A casting method for refining alloy phase in hypereutectic aluminum alloy

Abstract

The present invention belongs to the technical field of casting aluminum alloys, and discloses a casting method for refining alloy phases in hypereutectic aluminum alloys. Method: 1) According to the target alloy, a precursor mother alloy eutectic aluminum alloy and another precursor mother alloy hypereutectic aluminum alloy are determined, and the mixing ratio of the two is determined; according to the mixing ratio, the raw material containing aluminum intermediate alloy and / or pure aluminum are weighed respectively to obtain eutectic aluminum alloy raw material and hypereutectic aluminum alloy raw material; 2) The eutectic aluminum alloy raw material and the hypereutectic aluminum alloy raw material are respectively placed in a heating device for melting, standing and heat preservation, and refining and slag removal; 3) The two melts are mixed, standing and heat preservation, and cast. The method of the present invention effectively refines the alloy phase of the hypereutectic aluminum alloy containing Fe / Ni, so that the hypereutectic aluminum alloy has a uniform and fine structure, and the comprehensive performance effect is remarkable, and the thermal conductivity, mechanical and expansion properties of the aluminum alloy are simultaneously improved. The method is simple and easy to operate, with low production cost and wide applicability.

Description

Technical Field

[0001] The invention relates to the technical field of cast aluminum alloys, and in particular to a casting method for refining alloy phases in a hypereutectic aluminum alloy. Background Art

[0002] Aluminum has excellent properties such as low density, excellent thermal and electrical conductivity, and good corrosion resistance. Alloying it can further improve its mechanical properties, so that it has excellent comprehensive properties such as low density, high specific strength, and corrosion resistance. Aluminum alloy has become the second largest metal structural material after steel materials and is widely used in construction, automobiles and other fields. In addition to giving full play to the mechanical properties of aluminum alloys in the field of engineering structures, aluminum alloys are also widely used in the production and preparation of cables and heat dissipation devices by utilizing their functional properties such as thermal conductivity and electrical conductivity.

[0003] Si is the most widely used alloying element in aluminum alloys, among which Al-Si alloys are also common cast aluminum alloys. After Si is added, in addition to improving mechanics, it is also beneficial to improve the wear resistance of the alloy and reduce its thermal expansion coefficient, especially for Al-Si alloys with Si content exceeding the eutectic point (12.6%), such as A390 (16-18% Si, 4-5% Cu, 0.45-0.65% Mg, 0.2-0.5% Fe) alloy, which is widely used in engine pistons. However, Si will significantly reduce the thermal conductivity of aluminum alloys, especially when the Si phase is coarse and the solubility in the matrix is ​​large, the reduction is more significant. The thermal conductivity of A390 alloy produced based on casting process is generally 80-90W / (m·K), which is not suitable for fields with high requirements for heat dissipation performance, such as communication base station filters, heat dissipation substrates, etc. With the rapid development of new energy vehicles and other fields, it is more urgent to develop and control the organization and performance of aluminum alloys that have both high thermal conductivity and low thermal expansion properties, ensure the necessary mechanical properties, and are suitable for casting.

[0004] Among the common alloying elements of aluminum, Fe and Ni have low solubility in Al and have little effect on the thermal conductivity of Al. At the same time, Fe and Ni react with Al melt to form alloy phases with low thermal expansion coefficient, such as Al 13 Fe 4 , Al 3 Ni and Al 9FeNi. Comparing Fe and Ni, it is found that Fe is more conducive to reducing the thermal expansion coefficient, but the decrease in thermal conductivity is relatively large, while Ni has a relatively small effect on the thermal conductivity of aluminum alloys, but the decrease in thermal expansion coefficient is relatively low. Therefore, Al-Fe-Ni is a casting aluminum alloy system that is expected to achieve high thermal conductivity and low expansion performance. The thermal expansion coefficient of the material is mainly related to the volume fraction of the low expansion phase in the alloy. In order to reduce the thermal expansion coefficient of Al-Fe-Ni alloys, it is necessary to greatly increase the content of alloying elements to generate a large volume fraction of alloy phases. At this time, the alloy composition far exceeds the eutectic composition point, and the primary phase is bound to be coarse, resulting in poor product quality, which has an adverse effect on the mechanical, electrical and thermal conductivity of the alloy. Therefore, controlling the morphology and distribution of the primary phase is the key to preparing hypereutectic aluminum alloys with uniform structure, excellent mechanical and electrical / thermal conductivity. The methods of refining the primary phase can be mainly divided into two categories. One is the method of improving the casting process through technology, such as directional solidification, rapid solidification, electromagnetic solidification and semi-solid solidification technology, but the process is complicated, the equipment is expensive and the experimental conditions are relatively harsh; the other is the metamorphic refinement method, but it is easy to introduce other impurity elements.

[0005] For the typical hypereutectic Al-Si based casting aluminum alloy system, Chinese invention patent applications CN102839291A and CN102864350A disclose a method for preparing the primary silicon phase in the hypereutectic aluminum-silicon alloy without modification and refinement, and a hypereutectic aluminum-silicon alloy is obtained by mixing high silicon alloy and pure aluminum in different mass ratios. The preparation process is as follows: Al-25% Si and pure aluminum are melted in two electric furnaces respectively, and after refining and slag removal, the Al-25% Si alloy and the pure aluminum melt are mixed in a mass ratio of 2.57:1 to 7.33:1, and then properly stirred, left to stand and heat-insulated before casting. The prepared alloy does not need to be modified to obtain a primary silicon phase with small size and regular shape. The above two inventions are different from the traditional direct smelting to obtain specific component alloys. Instead, two different component alloys are melted separately at different temperatures, and then quickly cast after mixing, utilizing the more significant energy and concentration fluctuations in the melt to achieve microstructure refinement, especially the refinement of the primary Si phase in the hypereutectic Al-Si alloy.

[0006] The primary Si phase in the hypereutectic Al-Si alloy is directly precipitated from the Si component during the solidification process, while the primary phase of the hypereutectic Al alloy system containing Fe / Ni is precipitated through chemical reactions between components, which is significantly different from the hypereutectic Al-Si alloy system. Experiments show that the technology based on the above invention disclosure is not suitable for the primary phase refinement of the hypereutectic alloy system containing Fe / Ni.

[0007] For the alloy system containing Fe / Ni, Chinese patent application CN104658630A discloses a high electrical conductivity and high thermal conductivity aluminum-iron-nickel rare earth aluminum alloy. The application controls the addition of 0.2% to 0.6% Fe, 0.3% to 0.8% Ni, 0.2% to 0.6% mixed rare earth and 0.1% to 0.5% Mg / Cu / Mn additives to prepare an aluminum alloy with an electrical conductivity of ≥61.8% IACS and a thermal conductivity of ≥225W / (m·K). It has good electrical and thermal conductivity and is suitable for cable materials, but its linear expansion coefficient is relatively high. Chinese patent application CN113502419A discloses a high thermal conductivity and low expansion deformation aluminum alloy and its preparation method. The application improves the microstructure of the alloy by adding 1.5-2.5% Fe, 1.0-2.0% Ni, using Yb and / or Mg composite modification, and combining mechanical vibration casting, annealing and rolling deformation to achieve multi-objective balanced optimization of the alloy's thermal conductivity, thermal expansion coefficient and mechanical properties. However, the invention mainly achieves organizational refinement and performance improvement through rolling deformation, and the process is relatively complex and not suitable for the preparation of complex parts.

[0008] To solve the above problems, the present invention discloses a casting process for refining the primary phase of a hypereutectic alloy system containing Fe / Ni, which can well achieve the simultaneous improvement of thermal conductivity and mechanical properties, and prepare a hypereutectic alloy with a low thermal expansion coefficient, thereby meeting the current needs of communication base station filters, heat dissipation substrates and other fields for high thermal conductivity and low expansion cast aluminum alloys and their preparation. Summary of the invention

[0009] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a casting method for refining the alloy phase in a hypereutectic aluminum alloy. The most significant difference between the present invention and the traditional process is that the eutectic component alloy and the hypereutectic component alloy are melted separately at different temperatures, and then mixed in a certain proportion to obtain a hypereutectic component alloy melt, and finally quickly stirred, cast and cooled to obtain an ingot. The method of the present invention is simple, and refines the alloy phase in the hypereutectic aluminum alloy, so that the casting has significant advantages such as refined structure, low segregation, and low thermal cracking tendency, and achieves simultaneous improvement of thermal conductivity and mechanical properties, and obtains a hypereutectic alloy with a lower thermal expansion coefficient.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A casting method for refining alloy phases in a hypereutectic aluminum alloy comprises the following steps:

[0012] (1) Preparation of master alloy: design the target aluminum alloy according to the performance requirements, first determine the precursor master alloy eutectic aluminum alloy corresponding to the target alloy, i.e., the eutectic component alloy, and then calculate the composition of the hypereutectic component alloy, i.e., the hypereutectic aluminum alloy, according to the mass mixing ratio of the eutectic aluminum alloy and another precursor master alloy hypereutectic component alloy, i.e., the hypereutectic aluminum alloy, so that the mass ratio of each element in the melt after mixing is consistent with that of the target alloy; or design the composition of the hypereutectic component alloy, i.e., the hypereutectic aluminum alloy, according to the target alloy and the eutectic component alloy, i.e., the eutectic aluminum alloy, and design the mixing ratio of the eutectic aluminum alloy and the hypereutectic aluminum alloy according to the composition of the eutectic aluminum alloy and the hypereutectic aluminum alloy, so that the mass ratio of each element in the melt after mixing is consistent with that of the target alloy; weigh the raw materials containing aluminum master alloy and / or pure aluminum according to the mass mixing ratio of the eutectic aluminum alloy and the hypereutectic aluminum alloy and the content of the elements in the two in their respective alloys, so as to obtain the eutectic aluminum alloy raw material and the hypereutectic aluminum alloy raw material; the target alloy is a nickel-containing aluminum alloy and / or an iron-nickel-containing aluminum alloy;

[0013] (2) Melting the aluminum alloy: placing the eutectic aluminum alloy raw material and the hypereutectic aluminum alloy raw material in a heating device for melting, and keeping them still to obtain a eutectic aluminum alloy melt and a hypereutectic aluminum alloy melt;

[0014] (3) Melt refining and slag removal: refining and slag removal of the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt in step (2);

[0015] (4) Mixing the master alloy melt: mixing the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt of step (3), and keeping them still to obtain a melt of the target alloy;

[0016] (5) Mixed melt casting;

[0017] The eutectic aluminum alloy is a eutectic aluminum alloy containing nickel or iron-nickel, and the hypereutectic aluminum alloy is a hypereutectic aluminum alloy containing nickel or iron-nickel.

[0018] The precursor mother alloy eutectic aluminum alloy is a low melting point eutectic component alloy, and the other precursor mother alloy hypereutectic aluminum alloy is a high melting point hypereutectic component alloy.

[0019] Preferably, in the present invention, the mass mixing ratio of the low melting point eutectic component alloy to the high melting point hypereutectic component alloy is 1:1 to 1:4.

[0020] The melting temperature of the eutectic aluminum alloy raw material is the liquidus temperature of the eutectic aluminum alloy + 30 to + 80°C, and the melting temperature of the hypereutectic aluminum alloy raw material is the liquidus temperature of the hypereutectic aluminum alloy + 30 to + 80°C; the melting temperature of the hypereutectic aluminum alloy raw material is higher than the melting temperature of the eutectic aluminum alloy.

[0021] When the target alloy is Al-yNi alloy, y>6, the eutectic aluminum alloy is Al-6Ni alloy, and the hypereutectic aluminum alloy is Al-xNi, x>6 and x>y; the melting temperature of the eutectic aluminum alloy Al-6Ni is 650-720°C; the melting temperature of the hypereutectic Al-xNi alloy is 700-850°C;

[0022] When the target alloy is Al-mFe-nNi alloy, m>1.75, n>1.25, the eutectic aluminum alloy is Al-1.75Fe-1.25Ni alloy, the hypereutectic aluminum alloy is Al-xFe-yNi, x>1.75, y>1.25, and x>m, y>n; the melting temperature of the Al-1.75Fe-1.25Ni eutectic alloy is 660~720℃; the melting temperature of the Al-xFe-yNi alloy is 700~1000℃ (preferably 700~950℃).

[0023] The mixing described in step (4) refers to placing the eutectic aluminum alloy melt in the hypereutectic aluminum alloy melt and mixing them evenly.

[0024] Before mixing, the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt are cooled by 30-50°C, but at the same time the temperature of the melt is at or above the liquidus temperature. At this time, the temperature of the hypereutectic aluminum alloy melt is higher than the temperature of the eutectic aluminum alloy melt.

[0025] The mixed melt casting molding in step (5) refers to casting the mixed melt into a mold and naturally cooling and solidifying it.

[0026] When the target alloy in step (1) is an Al-yNi (y>6) alloy composition (mass ratio), the eutectic component alloy, i.e., the eutectic aluminum alloy, is an Al-6Ni alloy, and the hypereutectic component alloy, i.e., the hypereutectic aluminum alloy, is an Al-xNi (x>6 and x>y);

[0027] When the target alloy is Al-mFe-nNi alloy (m>1.75, n>1.25) (mass ratio, same throughout the text), the eutectic component alloy, i.e. the eutectic aluminum alloy, is Al-1.75Fe-1.25Ni alloy, and the hypereutectic component alloy, i.e. the hypereutectic aluminum alloy, is Al-xFe-yNi (x>1.75, y>1.25, and x>m, y>n).

[0028] In order to better understand the process steps of the present invention, the present invention combines Al-Ni and Al-Fe-Ni hypereutectic alloy systems as specific application examples to further explain the detailed process flow. For two typical hypereutectic alloys, the morphology and distribution of the alloy structure are effectively regulated, and the primary phase refinement in the hypereutectic alloy and the multi-objective balanced optimization of the alloy thermal conductivity, thermal expansion and mechanical properties are achieved.

[0029] A casting method for refining alloy phases in a hypereutectic aluminum alloy of the present invention is used for preparing a hypereutectic Al-Ni based alloy, and comprises the following steps:

[0030] (1-1) Preparation of master alloy: design the alloy composition (mass ratio, the same as in the whole text) of the target alloy Al-yNi (y>6) according to the performance requirements, determine one of the precursor master alloys to be a low melting point eutectic alloy Al-6Ni alloy from the target alloy, design the mass mixing ratio, and calculate the other precursor master alloy hypereutectic alloy component Al-xNi (x>6 and x>y) according to the mass mixing ratio, the mass ratio of the elements after the eutectic alloy component and the hypereutectic alloy component are mixed is consistent with the target alloy; calculate the amount of raw materials of the eutectic alloy and the hypereutectic Al-xNi alloy according to the mass mixing ratio, use pure aluminum and aluminum-nickel master alloy as raw materials, weigh the corresponding mass of pure aluminum and aluminum-nickel master alloy of the two precursor master alloys according to the ratio, and prepare the eutectic component alloy and the Al-xNi hypereutectic alloy; the eutectic component alloy is Al-6Ni alloy; the mass ratio of the eutectic component alloy to the Al-xNi master alloy is 1:1 to 1:4; the aluminum-nickel master alloy is Al-20Ni;

[0031] (1-2) Master alloy smelting: The weighed pure aluminum and Al-20Ni master alloy required for the two groups of master alloys are melted in two furnaces respectively, and kept still to obtain eutectic component alloy Al-6Ni melt and hypereutectic Al-xNi melt; the time of the standing and keeping still is 5 to 20 minutes;

[0032] (1-3) Refining and slag removal: removing slag from the surface of the alloy melt after melting in step (1-2) and performing refining and slag removal treatment; specifically, adding a refining agent and a slag removal agent, refining and slag removal, standing and heat preservation, and the standing and heat preservation time is 2 to 10 minutes;

[0033] (1-4) Mixing the master alloy melts: The two precursor alloy melts in step (1-3) are cooled to 20 to 50° C. above their liquidus temperature and mixed, specifically by pouring the low-temperature Al-6Ni melt into a crucible of the higher-temperature Al-xNi hypereutectic melt, pre-mixing, stirring, and standing to keep warm for 2 to 30 minutes;

[0034] (1-5) Mixed melt casting: The mixed melt in step (1-4) is cast into a mold, naturally cooled and solidified to obtain a hypereutectic Al-Ni alloy casting.

[0035] The optimal mass mixing ratio of the two precursor master alloy melts in step (1-2) is 1:4. The melting temperature of the low-temperature Al-6Ni melt alloy is 660-720°C; the melting temperature of the hypereutectic Al-xNi alloy is 700-850°C. The melting process is stirred, and the stirring time is 2-20 minutes. Melting the pure aluminum and the aluminum-nickel master alloy means melting the pure aluminum first, and after the melting is complete, adding the aluminum-nickel master alloy and stirring evenly.

[0036] The refining and slag removal in step (1-3) is performed by adding a refining agent and a slag removal agent by nitrogen blowing method. The commercial grades of the refining agent and the slag removal agent are YT-J-1 and YT-D-4 respectively. The ingredients are prepared in a ratio of 1:1 and then mixed evenly. The total addition amount is 1% of the weight of the melt. The holding temperature after refining is controlled to be 20 to 80°C above the liquidus temperature of the alloy.

[0037] The mixing speed in step (1-4) is 0.05 kg / s to 0.2 kg / s; and the stirring time is 2 to 10 min.

[0038] A casting process for refining alloy phases in a hypereutectic aluminum alloy of the present invention is used for preparing a hypereutectic Al-Fe-Ni based alloy, and comprises the following steps:

[0039] (2-1) Master alloy ingredients: According to the performance requirements, a target alloy Al-mFe-nNi alloy (m>1.75, n>1.25) (mass ratio, the same throughout the text) is designed. According to the target alloy, one of the precursor master alloys can be determined to be a low-melting-point eutectic alloy Al-1.75Fe-1.25Ni alloy. The mass mixing ratio of the two precursor master alloy melts is designed, and the other precursor master alloy hypereutectic alloy component Al-xFe-yNi (x>1.75, y>1.25, and x>m, y>n) is calculated according to the mass mixing ratio; the eutectic alloy is calculated according to the mass mixing ratio. The raw material ratio of gold and hypereutectic Al-xFe-yNi alloy is as follows: pure aluminum, aluminum-iron and aluminum-nickel master alloy are used as raw materials; pure aluminum, aluminum-iron and aluminum-nickel master alloy of corresponding mass of two precursor master alloys are weighed respectively according to the ratio to prepare eutectic component alloy and Al-xFe-yNi hypereutectic alloy; the eutectic component alloy is Al-1.75Fe-1.25Ni alloy; the mass ratio of the eutectic component alloy melt to the Al-xFe-yNi master alloy melt is 1:1 to 1:4; the aluminum-iron master alloy is Al-20Fe, and the aluminum-nickel master alloy is Al-20Ni;

[0040] (2-2) Master alloy smelting: The weighed pure aluminum, aluminum-iron master alloy and aluminum-nickel master alloy required for the two groups of master alloys are melted in two furnaces respectively, and kept still to obtain a low-temperature Al-1.75Fe-1.25Ni melt and a high-temperature hypereutectic Al-xFe-yNi melt; the time for the standing and keeping still is 5 to 20 minutes;

[0041] (2-3) Refining and slag removal: The specific steps are the same as the above-mentioned Al-Ni binary alloy preparation process step (1-3).

[0042] (2-4) Mixing the master alloy melts: The two precursor alloy melts in step (2-3) are cooled to 20 to 50° C. above their liquidus temperature and mixed, specifically by placing the Al-1.75Fe-1.25Ni eutectic melt with a lower temperature into a crucible of the Al-xFe-yNi hypereutectic melt with a higher temperature, pre-mixing, stirring, and standing to keep warm for 2 to 30 minutes;

[0043] (2-5) Mixed melt casting: The mixed melt in step (2-4) is cast into a mold, naturally cooled and solidified to obtain a hypereutectic Al-Fe-Ni alloy casting.

[0044] The optimal mass mixing ratio of the two precursor master alloy melts in step (2-2) is 1:4. The smelting temperature of the Al-1.75Fe-1.25Ni eutectic alloy is 660-720°C; the melting temperature of the Al-xFe-yNi alloy is 700-1000°C. The melting process is stirred, and the stirring time is 2-20 minutes. Melting the pure aluminum, aluminum-iron master alloy and aluminum-nickel master alloy means melting pure aluminum first, and after the pure aluminum is completely melted, adding the aluminum-iron master alloy and the aluminum-nickel master alloy and stirring them evenly.

[0045] In step (2-3), the refining and slag removal is performed by adding a refining agent and a slag removal agent by nitrogen blowing method. The commercial grades of the refining agent and the slag removal agent are YT-J-1 and YT-D-4 respectively. The ingredients are prepared in a ratio of 1:1 and then mixed evenly. The total addition amount is 1% of the weight of the melt. The holding temperature after refining is controlled to be 20 to 80°C above the liquidus temperature of the alloy.

[0046] The mixing speed in step (2-4) is 0.05 kg / s to 0.2 kg / s; and the stirring time is 2 to 10 min.

[0047] In order to better understand the method of the present invention, combined with the solidification characteristics of Fe and Ni aluminum alloys, the basic principle of the present invention for achieving alloy phase refinement in hypereutectic alloys is described as follows:

[0048] Alloy solidification characteristics: The solid solubility of Fe and Ni elements in the aluminum matrix is ​​extremely low (≤0.05wt%), and they react with Al to form Al at the aluminum-rich end. 9 FeNi,Al 13 Fe 4 (Al 3 Fe) and Al 3 Ni phase. For Al-Ni and Al-Fe-Ni alloys, especially highly alloyed hypereutectic alloys, the primary phase is generated by the mutual reaction between components, and a eutectic reaction occurs during the subsequent solidification process to form a eutectic structure.

[0049] Process principle: The casting process of the present invention is to mix high-temperature melt and low-temperature melt of different compositions into a target composition melt in a certain proportion, and obtain a casting through casting and solidification. Since the two precursor melts have a large temperature difference, the temperature of the high-temperature melt drops and the temperature of the low-temperature melt rises after mixing. Compared with heat transfer, solute diffusion is relatively slow, and non-local energy and more significant composition fluctuations are easily formed in the mixed melt. Under the quenching effect of the low-temperature melt, the solute micro-regions of the high-temperature melt rapidly nucleate under large supercooling and grow towards the low-temperature and high-concentration area. The propulsion direction of the solid / liquid interface is opposite to the solute diffusion direction. Under the control of the reverse diffusion mode, the influence of composition supercooling is small, and the primary phase is more inclined to equiaxed growth.

[0050] In particular, a casting process for refining alloy phases in a hypereutectic aluminum alloy of the present invention is to prepare a hypereutectic component alloy melt by melting a low-melting-point eutectic component alloy and a high-melting-point hypereutectic component alloy at different temperatures, and then mixing them in a certain proportion. Compared with the existing process for preparing a hypereutectic alloy based on mixing pure aluminum and a large hypereutectic melt, when the two melts are mixed in this process, since the melting point of the eutectic alloy is lower than that of pure aluminum, the high-temperature melt is more strongly chilled by the low-temperature melt, resulting in a greater degree of supercooling, so that the melt solute micro-regions rapidly nucleate; on the other hand, compared with the pure aluminum melt, the eutectic alloy melt provides more solute atoms, so that the solute diffusion distance during nucleation is shorter. Therefore, the process for preparing a hypereutectic alloy based on mixing eutectic and large hypereutectic melts of the present invention has a better effect on refining the primary phase generated by the mutual reaction between components. While regulating the morphology and distribution of the primary phase and the eutectic phase of the alloy, it is beneficial to the thermal conductivity, thermal expansion and mechanical properties of the alloy.

[0051] Compared with the existing casting process, it has the following outstanding advantages and beneficial effects:

[0052] (1) The present invention provides a casting process for refining the alloy phase in a hypereutectic aluminum alloy. The process is simple to operate. A high-temperature hypereutectic melt and a low-temperature eutectic melt are mixed, and a primary phase is precipitated through component reaction. This allows the casting to have significant advantages such as refined structure and low segregation, and is particularly conducive to achieving effective refinement of the primary phase.

[0053] (2) The Al-Ni and Al-Fe-Ni alloy systems of the present invention are simple and easy to prepare, the addition amount is easy to control, the alloy system elements used are low in cost, and the comprehensive performance is excellent.

[0054] (3) The Al-Ni and Al-Fe-Ni alloys prepared by the present invention successfully obtain fine, uniform, and high volume fraction Al 13 Fe 4 , Al 3 Ni and Al 9 FeNi phase, and the thermal expansion coefficient of these precipitated phases is relatively low; in addition, due to the low solid solubility of Fe and Ni elements, the effect on the thermal conductivity of the alloy is relatively small, achieving the balanced optimization of thermal conductivity, thermal expansion and mechanical properties of Al-Fe-Ni alloy.

[0055] (4) The thermal conductivity of the hypereutectic Al-Ni / Al-Fe-Ni alloy prepared by mixing eutectic and hypereutectic melts can reach 201.6 W / (m·K), and the expansion coefficient can be reduced to 16.4×10 -6 / K, compared with the mixing method based on pure aluminum and hypereutectic melt, the thermal conductivity is increased by 12.0%, the expansion coefficient is reduced by 6.3%, and the mechanical properties of the alloy are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The optical microstructure of the Al-10Ni alloy prepared by mixing pure aluminum and hypereutectic Al-13.3Ni alloy in a ratio of 1:3 (mass ratio) in Comparative Example 1;

[0057] Figure 2 XRD spectrum of Al-10Ni alloy prepared by mixing pure aluminum and hypereutectic Al-13.3Ni alloy in a ratio of 1:3 (mass ratio) in Comparative Example 1;

[0058] Figure 3 The optical microstructure of the Al-10Ni alloy prepared by mixing the eutectic Al-6Ni and the hypereutectic Al-11.3Ni alloy in a ratio of 1:3 (mass ratio) in Example 1;

[0059] Figure 4 The optical microstructure of the Al-3.5Fe-2.5Ni alloy prepared by mixing pure aluminum and hypereutectic Al-5Fe-3.3Ni alloy in a ratio of 1:3 (mass ratio) in Comparative Example 2;

[0060] Figure 5 XRD spectrum of Al-3.5Fe-2.5Ni alloy prepared by mixing pure aluminum and hypereutectic Al-5Fe-3.3Ni alloy in a ratio of 1:3 (mass ratio) in Comparative Example 2;

[0061] Figure 6 This is an optical microstructure diagram of the Al-3.5Fe-2.5Ni alloy prepared by mixing the eutectic Al-1.75Fe-1.25Ni and the hypereutectic Al-4.1Fe-2.9Ni in a ratio of 1:3 (mass ratio) in Example 4. DETAILED DESCRIPTION

[0062] The present invention is described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0063] Taking two typical non-Si hypereutectic alloys, Al-Ni and Al-Fe-Ni, as examples, the process flow and implementation effects are explained based on comparative examples and embodiments.

[0064] Comparative Example 1: Preparation of Al-10Ni alloy by mixing pure aluminum with hypereutectic Al-13.3Ni

[0065] This comparative example is similar to the technical route disclosed in the inventions of CN102839291A and CN102864350A. The alloy prepared in this comparative example is an Al-10Ni hypereutectic alloy (mass ratio, the same as in the whole text). Pure aluminum and Al-20Ni alloy are used as raw materials for batching, and two precursor melts of pure aluminum and hypereutectic Al-Ni alloy are smelted separately, and then mixed in a certain proportion to prepare an Al-10Ni alloy melt, and finally cast into shape. The specific steps and process parameters are as follows:

[0066] (1) Preparation of master alloys. According to the target composition Al-10Ni alloy, the two precursor master alloy compositions are determined to be pure aluminum and hypereutectic Al-13.3Ni alloy according to a mixing ratio (mass ratio) of 1:3, and the pure aluminum and Al-20Ni master alloy required for preparing the two precursor master alloys are weighed respectively.

[0067] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys is melted in furnaces A and B respectively, with the melting temperatures being 720°C and 800°C respectively. After all the aluminum is melted, add Al-20Ni master alloy into furnace B, stir for 2 minutes to make the composition uniform, and keep it at room temperature for 5 minutes to obtain the required pure aluminum melt and Al-13.3Ni alloy melt.

[0068] (3) Refining and slag removal: Remove the slag on the surface of the alloy melt after melting in step (2), mix the commercially available YT-J-1 refining agent and YT-D-4 slag removal agent in a ratio of 1:1, add them to the alloy melt by nitrogen blowing method for refining and slag removal, and let it stand and keep warm for 10 minutes.

[0069] (4) Mixing of master alloy melts. Cool the pure aluminum melt and Al-13.3Ni melt in step (3) to 680°C and 750°C respectively, then skim off the slag, and then pour the pure aluminum melt with a lower temperature into the Al-13.3Ni melt with a higher temperature, complete pre-mixing, stirring, and standing to keep warm for 5 minutes.

[0070] (5) Casting of mixed melt: The mixed melt in step (4) is cast into a metal mold preheated to 200°C, the size of the casting is 100 mm × 45 mm × 15 mm, and naturally cooled and solidified to obtain a hypereutectic Al-Ni alloy casting, and finally a sample is taken from the casting for analysis.

[0071] In order to characterize the microstructure and performance characteristics of the above alloys, the microstructure of the alloys was observed using an optical microscope (model: Lecia DFC, standard: JB / T7946-2017). The linear expansion coefficient of the alloys was measured using a thermal mechanical analyzer (model: TMAQ400). The linear expansion coefficient of the alloys was measured using a flash thermal conductivity meter (model: NETZSCHLFA, size: Thermal conductivity was measured using an electronic universal material testing machine (model: AG-X-100KN, standard: GB / T228-2010) to obtain tensile curves. The thermal conductivity and mechanical properties test methods are described below.

[0072] Thermal conductivity test:

[0073] The present invention strictly tests the thermal diffusion coefficient of aluminum alloy according to the test standard ASTME 1461. The test instrument is a Netzsch LFA-457 laser thermal conductivity tester. The sample size is The upper and lower surfaces are polished with 400-grit sandpaper to ensure the parallelism of the sample. Before the thermal diffusion coefficient test, graphite needs to be sprayed on the surface to increase the infrared emissivity of the sample surface and the absorption ratio of light energy. The specific heat of the sample is calculated using the Neumann-Kopp criterion. The density test is carried out using the Archimedes drainage method and the DH-300 density balance according to the national standard GB / T 1423-19. The result of multiplying the above three physical quantities is the thermal conductivity of the alloy. The calculation formula is as follows:

[0074] λ=α·C p ·ρ

[0075] Where λ is the thermal conductivity of the material, W / (m·K); α is the thermal diffusivity of the material, mm 2 / s;C p is the specific heat of the material, J / (g·K); ρ is the density of the material, g / cm 3 .

[0076] Thermal expansion performance test:

[0077] The present invention strictly tests the thermal expansion coefficient of aluminum alloy in accordance with the current national standard GB / T 4339-2008. The test equipment adopts TMA Q400. The test prepares a 15mm×4mm×4mm cuboid sample by wire cutting and turning. The upper and lower cylindrical surfaces are polished with 400-mesh sandpaper to ensure the parallelism of the two end surfaces. In this test, each group of alloys is heated to 250°C at a heating rate of 5°C / min. The computer records the sample length-temperature curve to obtain the change curve of the thermal expansion coefficient. The specific linear expansion coefficient is as follows:

[0078]

[0079] In the formula, α represents the linear expansion coefficient, K -1 ; Δl represents the length change, mm; l 0 represents the original length of the sample, mm; Δt represents the change in temperature, K.

[0080] Mechanical properties test:

[0081] The present invention conducts mechanical property tests on a Shimadzu AG-X100KN universal testing machine according to the national standard GB / T 228.1. The test sample is processed into a dumbbell shape by wire cutting, and the upper and lower surfaces are polished with 400-mesh sandpaper to eliminate the influence of defects on the experimental results. In this test, each group of alloys is tested 3 times at a tensile speed of 1 mm / min and room temperature (25°C), and the stress-strain curve is recorded to obtain performance data, and the average value is taken as the final test data.

[0082] The image and data were processed according to GB / T228.1 standard, and the displacement of the sliding part of the clamping section was removed. The gauge length of the sample was 25 mm, and the elongation δ was calculated according to the following formula:

[0083]

[0084] Where, δ is the elongation, %; l 0 is the gauge length of the specimen, mm; l 1 It is the length of the gauge part of the specimen after breaking, in mm.

[0085] Figure 1 This is the optical microstructure of the Al-10Ni alloy prepared in Comparative Example 1. Figure 2 XRD analysis results of Al-10Ni alloy prepared in Comparative Example 1. The microstructure of Al-10Ni alloy prepared by mixing pure aluminum and hypereutectic Al-13.3Ni is mainly composed of α-Al and Al 3 Ni phase composition, primary Al 3The Ni phase is in the shape of long strips, indicating that the mixed preparation method of pure aluminum and hypereutectic Al-13.3Ni alloy has no significant effect on the refinement of the primary phase in the hypereutectic Al-Ni alloy.

[0086] The thermal conductivity of the Al-10Ni alloy prepared by mixing pure aluminum and hypereutectic Al-13.3Ni alloy melt in Comparative Example 1 was tested. The thermal conductivity of the alloy prepared by this mixing method was 180 W / (m·K), and the thermal expansion coefficient was 19.2×10 - 6 K -1 (@100℃). The tensile strength and elongation of the Al-10Ni alloy under this mixing method were tested, and its tensile strength was only 155MPa and its elongation was 8.5%.

[0087] To further illustrate the implementation effect of the present invention, the present invention is described below in conjunction with embodiments.

[0088] Example 1: Preparation of Al-10Ni alloy by mixing eutectic Al-6Ni and hypereutectic Al-11.3Ni

[0089] The alloy prepared in this embodiment is the same as that in comparative example 1, which is an Al-10Ni alloy. The raw materials for preparing the alloy are also the same as those in comparative example 1, which are pure Al and Al-20Ni alloy. Similarly, two precursor melts are mixed to prepare the Al-10Ni target alloy, but the difference is that one of the precursor melts is a eutectic alloy. The specific steps and process parameters are as follows:

[0090] (1) Preparation of master alloys. According to the target composition Al-10Ni alloy, the compositions of the two precursor master alloys are determined to be eutectic Al-6Ni alloy and hypereutectic Al-11.3Ni alloy according to a mixing ratio of 1:3, and the pure aluminum and Al-20Ni master alloy required for preparing the two precursor master alloys are weighed respectively.

[0091] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys was melted in two furnaces at 700°C and 780°C respectively. After all the aluminum was melted, the Al-20Ni intermediate alloy required for preparing the two precursor master alloys was added to two electric furnaces respectively, stirred for 2 minutes to make the composition uniform, and then kept at room temperature for 5 minutes to obtain the required Al-6Ni melt and Al-11.3Ni alloy melt.

[0092] (3) Refining and slag removal: The two precursor master alloy melts melted in step (2) were subjected to refining and slag removal treatment, and then left to stand and keep warm. The specific operation was the same as step (3) of comparative example 1.

[0093] (4) Mixing of master alloy melts. The Al-6Ni melt and the Al-11.3Ni melt in step (3) are cooled to 660°C and 730°C respectively, and then the slag is removed. Then, the Al-6Ni melt with a lower temperature is poured into the Al-11.3Ni melt with a higher temperature, and the mixture is pre-mixed, stirred, and allowed to stand for 5 minutes.

[0094] (5) Casting the mixed melt: The mixed melt in step (4) is cast and molded, and finally a sample is taken from the casting for analysis.

[0095] The microstructural characteristics of the alloy prepared in this example were observed and analyzed. Figure 3 Figure 1 is an optical microstructure of the Al-10Ni alloy prepared by mixing eutectic Al-6Ni and hypereutectic Al-11.3Ni in Example 1. Compared with the Al-10Ni alloy prepared in Comparative Example 1, the alloy prepared by mixing eutectic Al-6Ni melt with hypereutectic Al-11.3Ni melt has coarse primary Al 3 The Ni phase transforms into relatively fine particles.

[0096] The test results show that the thermal conductivity of the alloy in this embodiment is 199.6 W / (m·K), the tensile strength is 194 MPa, the elongation is 10.8%, and the thermal expansion coefficient is 18.1×10 -6 K -1 (@100°C). Compared with the alloy prepared in comparative example 1, the comprehensive performance of the alloy prepared in this embodiment is significantly improved, with thermal conductivity increased by 10.9%, tensile strength increased by 24.9%, elongation increased by 27.1%, and thermal expansion coefficient decreased by 5.7%. This mixing method improves the microstructure morphology of the Al-10Ni alloy, and at the same time improves the thermal conductivity, mechanical and thermal expansion properties of the alloy.

[0097] Example 2: Preparation of Al-10Ni alloy by mixing eutectic Al-6Ni and hypereutectic Al-14Ni

[0098] The alloy prepared in this embodiment is the same as that in Example 1, and the raw materials for preparing the alloy are also the same as those in Example 1. Similarly, the Al-10Ni target alloy is prepared by mixing the eutectic melt and the hypereutectic melt, and the difference is the mixing ratio and melting temperature of the precursor melt. The specific steps and process parameters are as follows:

[0099] (1) Preparation of master alloys. According to the target composition Al-10Ni alloy, the compositions of the two precursor master alloys are determined to be eutectic Al-6Ni alloy and hypereutectic Al-14Ni alloy in a mixing ratio of 1:1, and the pure aluminum and Al-20Ni master alloy required for preparing the two precursor master alloys are weighed respectively.

[0100] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys was melted in two furnaces at 700°C and 800°C respectively. After all the aluminum was melted, the required Al-20Ni master alloy was added to the two electric furnaces respectively, stirred for 2 minutes to make the composition uniform, and then kept at room temperature for 5 minutes to obtain the required Al-6Ni melt and Al-14Ni alloy melt.

[0101] (3) Refining and slag removal: The two precursor master alloy melts melted in step (2) are subjected to refining and slag removal treatment, and then left to stand and keep warm. The specific operation is the same as step (3) of Example 1.

[0102] (4) Mixing of master alloy melts. The Al-6Ni melt and the Al-14Ni melt in step (3) are cooled to 660°C and 750°C respectively, and then the slag is removed. Then, the Al-6Ni melt with a lower temperature is poured into the Al-14Ni melt with a higher temperature, and the mixture is pre-mixed, stirred, and allowed to stand for 5 minutes.

[0103] (5) Casting the mixed melt: The mixed melt in step (4) is cast and molded, and finally a sample is taken from the casting for analysis.

[0104] The microstructure characteristics of the alloy in this embodiment were observed and analyzed. Compared with Comparative Example 1, in the alloy prepared by mixing eutectic Al-6Ni melt and hypereutectic Al-14Ni melt in this embodiment, the coarse primary Al 3 The size of the Ni phase is significantly reduced.

[0105] The test results show that the alloy has a thermal conductivity of 190.5 W / (m·K), a tensile strength of 188 MPa, an elongation of 10.3%, and a thermal expansion coefficient of 18.4×10 -6 K -1 (@100°C). Compared with the alloy prepared in Comparative Example 1, the comprehensive performance of the alloy in this embodiment is improved to a certain extent, with thermal conductivity increased by 5.8%, tensile strength increased by 21.4%, elongation increased by 21.4%, and thermal expansion coefficient decreased by 4.2%.

[0106] Example 3: Preparation of Al-10Ni alloy by mixing eutectic Al-6Ni and hypereutectic Al-11Ni

[0107] The alloy prepared in this embodiment is the same as that in embodiment 1, and the raw materials for preparing the alloy are also the same as those in embodiment 1. Similarly, the Al-10Ni target alloy is prepared by mixing the eutectic melt and the hypereutectic melt. The difference is the mixing ratio and melting temperature of the precursor melt. The specific steps and process parameters are as follows:

[0108] (1) Preparation of master alloys. According to the target composition Al-10Ni alloy, the compositions of the two precursor master alloys are determined to be eutectic Al-6Ni alloy and hypereutectic Al-11Ni alloy according to a mixing ratio of 1:4, and the pure aluminum and Al-20Ni master alloy required for preparing the two precursor master alloys are weighed respectively.

[0109] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys was melted in two furnaces at 700°C and 760°C respectively. After all the aluminum was melted, the required Al-20Ni master alloy was added to the two electric furnaces respectively, stirred for 2 minutes to make the composition uniform, and then kept at room temperature for 5 minutes to obtain the required Al-6Ni melt and Al-11Ni alloy melt.

[0110] (3) Refining and slag removal: The two precursor master alloy melts melted in step (2) are subjected to refining and slag removal treatment, and then left to stand and keep warm. The specific operation is the same as step (3) of Example 1.

[0111] (4) Mixing the master alloy melts. The Al-6Ni melt and the Al-11Ni melt in step (3) are cooled to 660°C and 720°C respectively, and then the slag is removed. Then, the Al-6Ni melt with a lower temperature is poured into the Al-11Ni melt with a higher temperature, stirred, and allowed to stand for 5 minutes.

[0112] (5) Casting the mixed melt: The mixed melt in step (4) is cast and molded, and finally a sample is taken from the casting for analysis.

[0113] The microstructure characteristics of the alloy in this embodiment were observed and analyzed. Compared with Comparative Example 1, the alloy prepared by mixing eutectic Al-6Ni melt with hypereutectic Al-11Ni high temperature melt has coarse primary Al 3 The Ni phase transforms into relatively fine particles, and the second phase is finely and evenly distributed on the aluminum matrix.

[0114] The test results show that the alloy has a thermal conductivity of 201.6 W / (m·K), a tensile strength of 201 MPa, an elongation of 11.3%, and a thermal expansion coefficient of 18.0×10 -6 K -1 (@100℃). Compared with the alloy prepared in Comparative Example 1, the comprehensive performance of the alloy prepared in this embodiment is significantly improved, with thermal conductivity increased by 12.0%, tensile strength increased by 29.7%, elongation increased by 33.2%, and thermal expansion coefficient decreased by 6.3%. This embodiment improves the microstructure morphology of the Al-10Ni alloy by mixing the eutectic melt with the hypereutectic melt, and achieves alloy structure refinement, multi-objective balanced optimization of thermal conductivity, mechanical and thermal expansion properties.

[0115] To further illustrate the implementation effect of the present invention, Al-Fe-Ni hypereutectic alloy is taken as an example below to illustrate the process flow and implementation effect based on comparative examples and embodiments.

[0116] Comparative Example 2: Preparation of Al-3.5Fe-2.5Ni alloy by mixing pure aluminum with hypereutectic Al-5Fe-3.3Ni

[0117] This comparative example is similar to the technical route disclosed in the inventions of CN102839291A and CN102864350A. The alloy prepared in this comparative example is Al-3.5Fe-2.5Ni hypereutectic alloy (mass ratio, the same as in the whole text). Pure aluminum, Al-20Fe and Al-20Ni alloy raw materials are used for batching, and two precursor melts of pure aluminum and hypereutectic Al-Fe-Ni alloy are smelted respectively, and then mixed in a certain proportion to prepare Al-3.5Fe-2.5Ni alloy melt, and finally cast into shape. The specific steps and process parameters are as follows:

[0118] (1) Preparation of master alloys. According to the target composition Al-3.5Fe-2.5Ni alloy, the compositions of the two precursor master alloys are determined to be pure aluminum and hypereutectic Al-5Fe-3.3Ni alloy in a mixing ratio of 1:3, and the pure aluminum, Al-20Fe and Al-20Ni master alloys required for preparing the two precursor master alloys are weighed respectively.

[0119] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys is melted in furnaces A and B, respectively, at melting temperatures of 720°C and 850°C. After all the aluminum is melted, the required Al-20Fe and Al-20Ni master alloys are added to furnace B, stirred for 2 minutes to make the composition uniform, and then left to stand for 5 minutes to obtain the required pure aluminum melt and Al-5Fe-3.3Ni alloy melt.

[0120] (3) Refining and slag removal: Remove the slag on the surface of the alloy melt after melting in step (2), mix the commercially available YT-J-1 refining agent and YT-D-4 slag removal agent in a ratio of 1:1, add them to the alloy melt by nitrogen blowing method for refining and slag removal, and let it stand and keep warm for 10 minutes.

[0121] (4) Mixing of master alloy melts. The pure aluminum melt and Al-5Fe-3.3Ni melt in step (3) are cooled to 680°C and 800°C respectively, and then the slag is removed. Then, the pure aluminum melt with a lower temperature is poured into the Al-5Fe-3.3Ni melt with a higher temperature, and the mixture is pre-mixed, stirred, and allowed to stand for 5 minutes.

[0122] (5) Casting of mixed melt: The mixed melt in step (4) is cast into a metal mold preheated to 200°C, the size of the casting is 100 mm × 45 mm × 15 mm, and naturally cooled and solidified to obtain a hypereutectic Al-Fe-Ni alloy casting, and finally a sample is taken from the casting for analysis.

[0123] The microstructure characteristics and phase composition of the alloy in this comparative example were observed and analyzed. Figure 4 is the optical microstructure diagram of the Al-3.5Fe-2.5Ni alloy in Comparative Example 2, Figure 5 XRD analysis results of Al-3.5Fe-2.5Ni alloy prepared by mixing pure aluminum and hypereutectic Al-5Fe-3.3Ni. The microstructure of the alloy prepared by mixing pure aluminum and hypereutectic Al-5Fe-3.3Ni is coarse (α-Al+Al 9 FeNi) and strip-shaped Al 13 Fe 4 , indicating that the process has limited effect on the refinement of the primary phase in the hypereutectic Al-Fe-Ni alloy formed by the reaction of the components. According to the test, the alloy of this comparative example has a thermal conductivity of 165W / (m·K), a tensile strength of 145MPa, an elongation of 6.5%, and a thermal expansion coefficient of 17.8×10 -6 K -1 (@100℃).

[0124] To further illustrate the implementation effect of the present invention, the present invention is described below in conjunction with embodiments, taking hypereutectic Al-3.5Fe-2.5Ni as an example.

[0125] Example 4: Preparation of Al-3.5Fe-2.5Ni alloy by mixing eutectic Al-1.75Fe-1.25Ni and hypereutectic Al-4.1Fe-2.9Ni

[0126] The alloy prepared in this embodiment is the same as that in comparative example 2, which is also an Al-3.5Fe-2.5Ni hypereutectic alloy. Pure aluminum, Al-20Fe and Al-20Ni alloy raw materials are used for batching, and two precursor melts of eutectic A1-1.75Fe-1.25Ni alloy and hypereutectic Al-Fe-Ni alloy are smelted respectively, and then mixed in a certain proportion to prepare Al-3.5Fe-2.5Ni alloy melt, and finally cast into shape. The specific steps and process parameters are as follows:

[0127] (1) Preparation of master alloys. According to the target composition of Al-3.5Fe-2.5Ni alloy, the compositions of the two precursor master alloys are determined to be Al-1.75Fe-1.25Ni and hypereutectic Al-4.1Fe-2.9Ni alloy at a mixing ratio of 1:3. The pure aluminum, Al-20Fe and Al-20Ni master alloys required to prepare the two precursor master alloys are weighed respectively.

[0128] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys was melted in two furnaces at 700°C and 820°C respectively. After all the aluminum was melted, the Al-20Fe and Al-20Ni intermediate alloys required for preparing the two precursor master alloys were added to two electric furnaces respectively, stirred for 2 minutes to make the composition uniform, and then kept at room temperature for 5 minutes to obtain the required Al-1.75Fe-1.25Ni melt and Al-4.1Fe-2.9Ni alloy melt.

[0129] (3) Refining and slag removal. The alloy melt after melting in step (2) is subjected to refining and slag removal treatment, and is allowed to stand for heat preservation. The specific operation is the same as step (3) in comparative example 2.

[0130] (4) Mixing of master alloy melts. The Al-1.75Fe-1.25Ni melt and the Al-4.1Fe-2.9Ni melt in step (3) are cooled to 670°C and 780°C respectively, and then the slag is removed. Then, the Al-1.75Fe-1.25Ni melt with a lower temperature is poured into the Al-4.1Fe-2.9Ni melt with a higher temperature, and the mixture is pre-mixed, stirred, and allowed to stand for 5 minutes.

[0131] (5) Casting of the mixed melt: The mixed melt in step (4) is cast to obtain a hypereutectic Al-Fe-Ni alloy casting, and finally a sample is taken from the casting for analysis.

[0132] The microstructural characteristics of the alloy of this example were observed and analyzed. Figure 6 Figure 2 is an optical microstructure diagram of the Al-3.5Fe-2.5Ni alloy in Example 4. Compared with Comparative Example 2, the alloy prepared by mixing the eutectic melt with the hypereutectic melt has a coarse microstructure (α-Al+Al 9 FeNi) and primary Al 13 Fe 4 Phase transformation into fine alloy structure.

[0133] The alloy prepared in this embodiment has a thermal conductivity of 186.9 W / (m·K), a tensile strength of 182 MPa, an elongation of 8.1%, and a thermal expansion coefficient of 16.5×10 -6 K -1(@100°C). Compared with the alloy prepared in Comparative Example 2, the comprehensive performance of the alloy in this embodiment is significantly improved, with thermal conductivity increased by 13.3%, tensile strength increased by 25.7%, elongation increased by 25.1%, and thermal expansion coefficient decreased by 7.3%.

[0134] Example 5: Preparation of Al-3.5Fe-2.5Ni alloy by mixing eutectic Al-1.75Fe-1.25Ni and hypereutectic Al-5.3Fe-3.8Ni

[0135] The alloy prepared in this embodiment is the same as that in embodiment 4, and the raw materials for preparing the alloy are also the same as those in embodiment 4. Similarly, the eutectic Al-1.75Fe-1.25Ni melt and the hypereutectic Al-Fe-Ni melt are mixed to prepare the Al-3.5Fe-2.5Ni target alloy, and the difference is the mixing ratio and melting temperature of the precursor melt. The specific steps and process parameters are as follows:

[0136] (1) Preparation of master alloys. According to the target composition of Al-3.5Fe-2.5Ni alloy, the compositions of the two precursor master alloys are determined to be Al-1.75Fe-1.25Ni and hypereutectic Al-5.3Fe-3.8Ni alloy in a mixing ratio of 1:1. The pure aluminum, Al-20Fe and Al-20Ni master alloys required to prepare the two precursor master alloys are weighed respectively.

[0137] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys is melted in two furnaces at 700°C and 850°C respectively. After all the aluminum is melted, the required Al-20Fe and Al-20Ni master alloys are added to two electric furnaces respectively, stirred, and allowed to stand to keep warm, to obtain the required Al-1.75Fe-1.25Ni melt and Al-5.3Fe-3.8Ni alloy melt.

[0138] (3) Refining and slag removal: The alloy melt after the melting in step (2) is refined and slag removed, and then left to stand and keep warm. The specific operation is the same as step (3) in Example 4.

[0139] (4) Mixing of master alloy melts. The Al-1.75Fe-1.25Ni melt and the Al-5.3Fe-3.8Ni melt in step (3) are cooled to 670°C and 800°C respectively, and then the slag is removed. Then, the Al-1.75Fe-1.25Ni melt with a lower temperature is poured into the Al-5.3Fe-3.8Ni melt with a higher temperature, and the pre-mixing is completed, stirred, and allowed to stand for 5 minutes.

[0140] (5) Casting of the mixed melt: The mixed melt in step (4) is cast to obtain a hypereutectic Al-Fe-Ni alloy casting, and finally a sample is taken from the casting for analysis.

[0141] The microstructure characteristics of the alloy of this embodiment were observed and analyzed. Compared with Comparative Example 2, the alloy prepared by mixing the eutectic melt and the hypereutectic melt has a coarse microstructure (α-Al+Al 9 FeNi) and Al 13 Fe 4 After testing, the alloy prepared in this embodiment has a thermal conductivity of 182W / (m·K), a tensile strength of 179MPa, an elongation of 7.9%, and a thermal expansion coefficient of 17.0×10 -6 K -1 (@100°C). Compared with the alloy prepared by mixing pure aluminum with hypereutectic Al-5.3Fe-3.8Ni in comparative example 2, the comprehensive performance of the alloy in this embodiment is improved, with thermal conductivity increased by 10.3%, tensile strength increased by 23.3%, elongation increased by 21.9%, and thermal expansion coefficient decreased by 4.5%.

[0142] Example 6: Preparation of Al-3.5Fe-2.5Ni alloy by mixing eutectic Al-1.75Fe-1.25Ni and hypereutectic Al-3.9Fe-2.8Ni

[0143] The alloy prepared in this embodiment is the same as that in embodiment 4, and the raw materials for preparing the alloy are also the same as those in embodiment 4. Similarly, the Al-3.5Fe-2.5Ni eutectic melt and the Al-Fe-Ni hypereutectic melt are mixed to prepare the Al-3.5Fe-2.5Ni target alloy. The difference is the mixing ratio of the precursor melt and the melting temperature. The specific steps and process parameters are as follows:

[0144] (1) Preparation of master alloys. According to the target composition Al-3.5Fe-2.5Ni alloy, the compositions of the two precursor master alloys are determined to be Al-1.75Fe-1.25Ni and hypereutectic Al-3.9Fe-2.8Ni alloy according to a mixing ratio of 1:4, and the pure aluminum, Al-20Fe and Al-20Ni master alloys required for preparing the two precursor master alloys are weighed respectively.

[0145] (2) Master alloy smelting. The weighed pure aluminum required for the two sets of master alloys is melted in two furnaces at 700°C and 800°C respectively. After all the aluminum is melted, the required Al-20Fe and Al-20Ni intermediate alloys are added to two electric furnaces respectively, stirred, and allowed to stand to keep warm to obtain the required Al-1.75Fe-1.25Ni melt and Al-3.9Fe-2.8Ni alloy melt.

[0146] (3) Refining and slag removal: The alloy melt after the melting in step (2) is refined and slag removed, and then left to stand and keep warm. The specific operation is the same as step (3) in Example 4.

[0147] (4) Mixing the master alloy melts. The Al-1.75Fe-1.25Ni melt and the Al-3.9Fe-2.8Ni melt in step (3) are cooled to 670°C and 760°C respectively, and then the slag is removed. Then, the Al-1.75Fe-1.25Ni melt with a lower temperature is poured into the Al-3.9Fe-2.8Ni melt with a higher temperature, stirred, and allowed to stand to keep warm.

[0148] (5) Casting of the mixed melt: The mixed melt in step (4) is cast to obtain a hypereutectic Al-Fe-Ni alloy casting, and finally a sample is taken from the casting for analysis.

[0149] The microstructure characteristics and phase composition of the alloy of this embodiment were observed and analyzed. Compared with Comparative Example 2, the alloy prepared by mixing the eutectic melt and the hypereutectic melt has a coarse microstructure (α-Al+Al 9 FeNi) and Al 13 Fe 4 It transforms into a relatively fine alloy structure, and the second phase is finely and evenly distributed on the aluminum matrix.

[0150] The test results show that the alloy has a thermal conductivity of 190 W / (m·K), a tensile strength of 191 MPa, an elongation of 8.3%, and a thermal expansion coefficient of 16.4×10 -6 K -1 (@100°C). Compared with the alloy prepared by mixing pure aluminum with hypereutectic Al-5Fe-4Ni in comparative example 2, the comprehensive performance of the alloy prepared in this embodiment is significantly improved, with thermal conductivity increased by 15.2%, tensile strength increased by 31.7%, elongation increased by 27.8%, and thermal expansion coefficient decreased by 7.9%. This embodiment improves the microstructure morphology of the Al-3.5Fe-2.5Ni alloy, realizes alloy structure refinement, and multi-objective balanced optimization of improved thermal conductivity, mechanical and thermal expansion properties.

[0151] In order to better compare and illustrate the differences in the processes and effects of each comparative example and embodiment, the experimental parameters and performance data are summarized in Table 1 and Table 2, respectively. All embodiments of the present invention prepare hypereutectic alloys by a process based on mixing a eutectic melt with a large hypereutectic melt, and this process can simultaneously improve the microstructure, thermal conductivity, mechanical and thermal expansion properties of the alloy. In particular, the comprehensive performance of Example 3 and Example 6 prepared based on the mixing of a eutectic melt and a hypereutectic melt is better than that of Al-10Ni and Al-3.5Fe-2.5Ni alloys prepared based on the mixing of pure aluminum and a hypereutectic melt in Comparative Examples 1 and 2, while refining the microstructure, the thermal conductivity, mechanical properties and thermal expansion properties of the hypereutectic Al-Fe-Ni cast aluminum alloy are simultaneously improved.

[0152] Table 1 Experimental parameters of Comparative Examples 1-2 and Examples 1-6

[0153]

[0154] Table 2 Properties of alloys in comparative examples and examples

[0155]

[0156] Note: The improvement is calculated for the same target alloy under the same conditions.

[0157] The implementation methods of the present invention are not limited to the embodiments described, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A casting method for refining alloy phase in hypereutectic aluminum alloy, characterized in that: The steps include: (1) Preparation of master alloy: design the target aluminum alloy according to the performance requirements, first determine the corresponding precursor master alloy eutectic aluminum alloy according to the target alloy, and then calculate the composition of the hypereutectic aluminum alloy according to the mass mixing ratio of the eutectic aluminum alloy and another precursor master alloy hypereutectic aluminum alloy, so that the mass ratio of each element in the melt after mixing is consistent with the target alloy; or design the composition of the hypereutectic aluminum alloy according to the target alloy and the eutectic aluminum alloy, and design the mixing ratio of the eutectic aluminum alloy and the hypereutectic aluminum alloy according to the eutectic aluminum alloy and the hypereutectic aluminum alloy, so that the mass ratio of each element in the melt after mixing is consistent with the target alloy; according to the mass mixing ratio of the eutectic aluminum alloy and the hypereutectic aluminum alloy and the content of the elements in the two in their respective alloys, weigh the raw material containing aluminum master alloy and / or pure aluminum respectively, so as to obtain the eutectic aluminum alloy raw material and the hypereutectic aluminum alloy raw material; the target alloy is a nickel-containing aluminum alloy and / or an iron-nickel-containing aluminum alloy; (2) melting the aluminum alloy: placing a eutectic aluminum alloy raw material and a hypereutectic aluminum alloy raw material in a heating device for melting, respectively, and keeping the temperature, thereby obtaining a eutectic aluminum alloy melt and a hypereutectic aluminum alloy melt; (3) melt refining and slag removal: refining and slag removal of the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt in step (2); (4) Mixing the master alloy melt: mixing the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt of step (3), and keeping them still to obtain a melt of the target alloy; (5) Mixed melt casting; The eutectic aluminum alloy is a eutectic aluminum alloy containing nickel or iron-nickel, and the hypereutectic aluminum alloy is a hypereutectic aluminum alloy containing nickel or iron-nickel; After melting in step (2), stir and mix, and then let stand and keep warm; the time of standing and keeping warm is 5 to 20 minutes; Step (3) refining and deslagging treatment refers to adding a refining agent and a deslagging agent, refining and deslagging, and standing to keep warm; Before mixing in step (4), the eutectic aluminum alloy melt and the hypereutectic aluminum alloy melt are cooled by 30-50° C., but at the same time, the temperature of the melt is at or above the liquidus temperature, and the temperature of the hypereutectic aluminum alloy melt is higher than the temperature of the eutectic aluminum alloy melt; The time of keeping the mixture at room temperature in step (4) is 2 to 30 minutes; The raw material aluminum-containing master alloy in step (1) is an aluminum-nickel master alloy and / or an aluminum-iron master alloy; when the target alloy is Al- y When the Ni alloy is used, the raw material contains an aluminum master alloy, which is an aluminum-nickel master alloy; The target alloy is Al- m Fe- n When the Ni alloy is used, the raw material contains aluminum master alloys such as aluminum-nickel master alloy and aluminum-iron master alloy; The casting temperature in step (5) is maintained at 700-850°C; The target alloy is Al- y When Ni alloy is used, y >6, eutectic aluminum alloy is Al-6Ni alloy, hypereutectic aluminum alloy is Al- x Ni, x >6 and x > y ; The melting temperature of the eutectic aluminum alloy Al-6Ni is 660~720℃; the hypereutectic aluminum alloy Al- x The melting temperature of Ni alloy is 700~850℃; The target alloy is Al- m Fe- n When Ni alloy is used, m >1.75, n >1.25, eutectic aluminum alloy is Al-1.75Fe-1.25Ni alloy, hypereutectic aluminum alloy is Al- x Fe- y Ni, x >1.75, y >1.25, and x > m , y > n ; The melting temperature of the Al-1.75Fe-1.25Ni eutectic alloy is 660~720℃; x Fe- y The melting temperature of Ni alloy is 700~1000℃.

2. The casting method for refining the alloy phase in a hypereutectic aluminum alloy according to claim 1, characterized in that: The mass mixing ratio of the eutectic aluminum alloy to the hypereutectic aluminum alloy is 1:1 to 1:

4.

3. The casting method for refining the alloy phase in a hypereutectic aluminum alloy according to claim 1, characterized in that: The melting temperature of the eutectic aluminum alloy raw material is the liquidus temperature of the eutectic aluminum alloy + 30~+80°C, and the melting temperature of the hypereutectic aluminum alloy raw material is the liquidus temperature of the hypereutectic aluminum alloy + 30~+80°C; the melting temperature of the hypereutectic aluminum alloy raw material is higher than the melting temperature of the eutectic aluminum alloy.

4. The casting method for refining the alloy phase in a hypereutectic aluminum alloy according to claim 1, characterized in that: The refining and slag removal in step (3) is performed by adding a refining agent and a slag removal agent by nitrogen blowing method. The commercial grades of the refining agent and the slag removal agent are YT-J-1 and YT-D-4, respectively. The ingredients are prepared in a 1:1 ratio and then mixed evenly. The total addition amount is 1% of the weight of the melt. The standing and heat preservation time in step (3) is 2 to 30 minutes.

5. The casting method for refining the alloy phase in a hypereutectic aluminum alloy according to claim 1, characterized in that: The mixing in step (4) refers to adding the eutectic aluminum alloy melt into the hypereutectic aluminum alloy melt and mixing them, and the mixing rate is maintained at 0.05kg / s to 0.2kg / s; the mixing method is to pour the low-temperature melt into the high-temperature melt; In step (4), the stirring time after mixing is 2 to 20 minutes.

6. The casting method for refining the alloy phase in a hypereutectic aluminum alloy according to claim 1, characterized in that: The aluminum-nickel master alloy is Al-20Ni; the aluminum-iron master alloy is Al-20Fe.

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