Multi-element eutectic cast aluminum alloy suitable for brazing and preparation method of multi-element eutectic cast aluminum alloy

Abstract

The invention discloses a multi-element eutectic casting aluminum alloy suitable for brazing and a preparation method of the multi-element eutectic casting aluminum alloy. The multi-element eutectic casting aluminum alloy comprises Al, Mn, Ni, Fe, X, RE and unavoidable impurities. X is Ti and / or Cr, and RE is Ce and / or La; a plurality of eutectic reactions can occur in the solidification process to form an organization structure composed of primary alpha-Al and a multi-element eutectic organization; the multi-element eutectic structure comprises three or more of eutectic second phases of an alpha-Al phase, an Al6M phase, an Al11RE3 phase, an Al8REM4 phase, an Al23RE4M6 phase, an Al3M phase, an Al9M2 phase and the like, and M is at least one of Mn, Fe and Ni; during preparation, all the components are melted and refined and can be further cast into a casting; the aluminum alloy has good high-temperature structure stability, the mechanical property change before and after brazing is not large, and the requirements of castings for high-temperature brazing in the fields of electronic equipment, new energy automobiles and the like can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, in particular to the field of cast aluminum alloys, and specifically to a multi-element eutectic cast aluminum alloy suitable for brazing and a preparation method thereof. Background Art

[0002] At present, the water-cooled / liquid-cooled radiators of electronic equipment and the valve bodies of the thermal management systems of new energy vehicles are all made of aluminum alloy. These products are generally made of 6000 series aluminum alloys, which are forged and machined and then brazed and assembled with 3000 series or 6000 series plates. However, the production process of forgings is long, complex components cannot be prepared, and the effective yield rate is low, and the product cost is high. Casting, as a near-net-shape forming technology, can realize the forming of thin-walled, complex structures, and high-precision parts. Only a small amount of processing or even no processing is required to complete the preparation of parts. However, the solidus temperature of the current mainstream aluminum-silicon cast aluminum alloy is generally below 580℃, which cannot meet the brazing temperature requirement of 590-610℃ (brazing refers to a welding method in which the solder and the weldment below the melting point of the weldment are heated to the melting temperature of the solder at the same time, and the gap between the solid workpieces is filled with liquid solder to connect the metals).

[0003] An improved cast aluminum alloy suitable for brazing is disclosed. The cast aluminum alloy comprises the following components in terms of mass percentage: Mn 1.0-3.0%, Fe 0.1-1.0%, Cu 0.05-1.0%, M1 0.02-0.6%, M20.02-1.0%, the balance being Al and inevitable impurities, M1 being a combination of one or two selected from Ti and Zr, and M2 being a combination of one or more selected from V, Mo, and Cr; also disclosed is a brazable cast aluminum alloy, which comprises, in weight percentage, Mn: 1.0wt.%-2.2wt.%, Ni: 0.3wt.%-2.0wt.%, Fe: 0.05wt.%-0.8wt.%, Mg: 0.02wt.%-0.8wt.%, X: 0.01wt.%-0.8wt.%, X being a combination of one or more selected from Ti, Zr, and Cr; the balance being Al and inevitable impurities. However, practice has found that they have more or less deficiencies in the following aspects: 1. The requirements for process control are high, the temperature operation window is relatively narrow, and the requirements for equipment and operators are high; 2. Generally speaking, the higher the temperature of the melt before casting, the more conducive it is to control the thermal cracking tendency during casting, but for the equipment, it needs to accept a higher temperature melt, which increases the load on the equipment. If the temperature of the melt before casting is lowered, the thermal cracking tendency will be obvious and difficult to control; 3. It is impossible to take into account both strength and corrosion resistance, and there is a problem of losing one while gaining the other. Summary of the invention

[0004] The purpose of the present invention is to overcome one or more deficiencies in the prior art and to provide a new multi-element eutectic cast aluminum alloy suitable for brazing, which at least solves one problem existing in the prior art.

[0005] The present invention also provides a method for preparing a multi-element eutectic cast aluminum alloy suitable for brazing and an application of the same in preparing metal products.

[0006] In order to achieve the above object, a technical solution adopted by the present invention is:

[0007] A multi-element eutectic cast aluminum alloy suitable for brazing, the cast aluminum alloy comprising Al, Mn, Ni, Fe, X and RE, and unavoidable impurities;

[0008] Wherein, X is Ti and / or Cr, RE is Ce and / or La;

[0009] During the solidification process, a variety of eutectic reactions occur, forming an organizational structure composed of primary α-Al and multi-element eutectic structures;

[0010] The multi-element eutectic structure includes a eutectic second phase, and the eutectic second phase includes a eutectic α-Al phase, an Al6M phase, an Al 11 RE3 phase, Al8REM4 phase, Al 23 Three or more of RE4M6 phase, Al3M phase, Al9M2 phase, wherein M is one or a combination of two or a combination of three of Mn, Fe, and Ni;

[0011] The melting point of the eutectic second phase is above 620°C;

[0012] The unavoidable impurities include Mg, Cu, Si or Zn, and in terms of weight percentage, the Si content is controlled to be ≤0.2wt.%, the Mg content is ≤0.1wt.%, the Cu content is ≤0.1wt.%, the Zn content is ≤0.1wt.%, and the total impurity content is less than or equal to 0.3wt.%.

[0013] Al is an aluminum element, Mn is a manganese element, Fe is an iron element, Ni is a nickel element, Ti is a titanium element, Cr is a chromium element, Ce is a cerium element, La is a lanthanum element, Mg is a magnesium element, Cu is a copper element, Si is a silicon element, and Zn is a zinc element.

[0014] In some embodiments of the present invention, the mass ratio of Ni to RE is 0.3-3.5:1.

[0015] Furthermore, the mass ratio of Ni to RE is 0.35-2.0:1.

[0016] In some embodiments of the present invention, the cast aluminum alloy includes, in terms of weight percentage: Mn: 1.0wt.%~2.0wt.%; Ni: 1.5wt.%~3.5wt.%; Fe: 0.05wt.%~0.5wt.%; RE: 0.05wt.%~5.5wt.%; X: 0.05wt.%~0.4wt.%.

[0017] Furthermore, in terms of weight percentage, the cast aluminum alloy includes: Mn: 1.2wt.% to 1.8wt.%; Ni: 1.8wt.% to 3.5wt.%; Fe: 0.1wt.% to 0.4wt.%; RE: 0.5wt.% to 5.5wt.%; X: 0.1wt.% to 0.35wt.%.

[0018] Furthermore, in terms of weight percentage, the cast aluminum alloy includes: Mn: 1.4wt.%~1.8wt.%; Ni: 1.9wt.%~3.3wt.%; Fe: 0.15wt.%~0.35wt.%; RE: 1.0wt.%~5.3wt.%; X: 0.15wt.%~0.30wt.%.

[0019] In some embodiments of the present invention, the mass ratio of Mn to X is 5-9:1.

[0020] In some embodiments of the present invention, the area of ​​the multi-element eutectic structure accounts for 30% to 60% of the total area of ​​the alloy structure. Further, according to some specific aspects of the present invention, the area of ​​the multi-element eutectic structure accounts for more than 31% of the total area of ​​the alloy structure.

[0021] In some embodiments of the present invention, the eutectic second phase is in the shape of blocks, lamellar sheets, fibers, short rods or worms.

[0022] In some embodiments of the present invention, when RE is Ce, the multi-element eutectic structure includes at least eutectic α-Al phase, Al6 (Fe, Mn, Ni) phase, Al3 (Ni, Mn), AlCeMn phase, Al 11 Ce3 phase.

[0023] In some embodiments of the present invention, the solidification interval value of the cast aluminum alloy is less than 30°C.

[0024] According to some specific aspects of the present invention, the melt temperature of the cast aluminum alloy before casting can be less than or equal to 725°C.

[0025] In some embodiments of the present invention, in the cast state, the cast aluminum alloy has a tensile strength of more than 170 MPa, a yield strength of more than 85 MPa, and an elongation of greater than or equal to 8% at room temperature.

[0026] In some embodiments of the present invention, after brazing, the cast aluminum alloy has a tensile strength of more than 165 MPa, a yield strength of more than 80 MPa, and an elongation of greater than or equal to 12% at room temperature.

[0027] Another technical solution provided by the present invention is a method for preparing the above-mentioned multi-element eutectic cast aluminum alloy suitable for brazing, the preparation method comprising:

[0028] Weigh each component according to the formula amount, melt it, and obtain a melt;

[0029] adding a refining aid to the melt to obtain a metal melt after refining;

[0030] The metal melt is cooled to obtain the cast aluminum alloy.

[0031] Another technical solution provided by the present invention is: an aluminum alloy casting suitable for brazing, which is made by melting and then casting the multi-element eutectic cast aluminum alloy suitable for brazing, or by melting and refining the raw material components of the multi-element eutectic cast aluminum alloy suitable for brazing;

[0032] The melt temperature before casting can be less than or equal to 725°C.

[0033] Another technical solution provided by the present invention is a metal product, which is made by brazing the above-mentioned aluminum alloy casting suitable for brazing with other metal materials; further, the brazing temperature is 590-620°C.

[0034] In some embodiments of the present invention, the metal product is a water-cooled and / or liquid-cooled radiator for electronic equipment, or a valve body for a thermal management system of a new energy vehicle.

[0035] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0036] Based on one or more of the problems of difficult control of existing processes, low strength before and after brazing, inability to balance strength and corrosion resistance, and insufficient hot cracking performance, the present invention innovatively provides a novel Al-Mn-Ni-Fe-RE-X multi-electroctic alloy formula system. The alloy abandons the strengthening elements Mg and Cu conventionally used for reinforcement. In fact, in the Al-Mn-Ni-Fe-RE-X system of the present invention, the addition of Mg and Cu will cause unexpected performance degradation and even serious hot cracking. In particular, the alloy system of the present invention can eliminate and / or inhibit hot cracking in a relatively narrow temperature operating window and at a relatively low melt temperature before casting, thereby reducing the difficulty of operation and the stringent requirements on equipment. In addition, the alloy system of the present invention also achieves balance and balance in terms of corrosion resistance and strength.

[0037] Furthermore, in the Al-Mn-Ni-Fe-RE-X system of the present invention, the appropriate addition of Mn can increase the eutectic content, improve the strength, and ensure good fluidity, which is also beneficial to the demoulding of the casting; in addition, the addition of Mn can also provide a part of the solid solution strengthening and post-weld precipitation strengthening effects, and the appropriate addition can also avoid the formation of large-sized primary phases;

[0038] In the Al-Mn-Ni-Fe-RE-X system of the present invention, the addition of appropriate Fe can optimize the morphology, quantity and size of the eutectic second phase, avoid the formation of a large-sized primary phase, and also promote demolding;

[0039] In the Al-Mn-Ni-Fe-RE-X system of the present invention, the addition of appropriate Ni can increase the eutectic content and reduce the tendency of thermal cracking; and the Ni-containing eutectic second phase has a fine fiber structure, which can effectively improve the strength; in particular, the presence of the Ni-containing phase usually reduces the corrosion resistance of the material, but in the Al-Mn-Ni-Fe-RE-X of the present invention, through the optimization and synergistic effect of the components, the present invention can still achieve the suppression of corrosion resistance and even improve it at a relatively high nickel content, thereby achieving a balance and consideration of various performance aspects;

[0040] In the Al-Mn-Ni-Fe-RE-X system of the present invention, the addition of appropriate Ce and / or La can increase the eutectic content, improve the strength, and improve the casting performance. At the same time, Ce and La will also have a certain positive and beneficial effect on the morphology, size, and type of the second phase, and can avoid the formation of a coarse phase, ensuring that the elongation meets the requirements; and the Ce / La phase can improve the corrosion resistance by optimizing the corrosion itself rather than the aluminum matrix during the corrosion process, thereby overcoming the negative impact of the presence of the Ni-containing phase on the corrosion resistance;

[0041] In the Al-Mn-Ni-Fe-RE-X system of the present invention, appropriate addition of Ti can increase the number of nucleation particles in the α-Al matrix, achieve grain refinement, and further delay the dendrite bridging time and reduce the thermal cracking tendency; at the same time, Ti and Cr are also important dispersed phase forming elements, which can promote the precipitation of dispersed phase after brazing, thereby ensuring the mechanical properties before and after brazing;

[0042] In addition, in the Al-Mn-Ni-Fe-RE-X system of the present invention, the addition of Mg, Si, Cu and Zn will significantly reduce the solidus line and expand the solidification range, so the thermal cracking tendency is more obvious; at the same time, Zn will volatilize during the brazing process and pollute the brazing furnace. Therefore, in the present invention, they are all regarded as impurities to reduce their content in the system as much as possible.

[0043] The present invention optimizes the alloy formula system to form a multi-element eutectic alloy system, and under the synergistic and complementary effects of various elements, while taking into account both strength and corrosion resistance, it can also eliminate and / or inhibit hot cracking in a relatively narrow temperature operation window and at a relatively low melt temperature before casting, thereby reducing the difficulty of operation and the stringent requirements on equipment, and facilitating large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The thermodynamic phase diagram calculation result diagram of the alloy composition corresponding to Example 3;

[0045] Figure 2 Obtain the as-cast structure diagram corresponding to the casting for Example 3;

[0046] Figure 3 The brazed state microstructure diagram of the casting after brazing treatment is obtained for Example 3;

[0047] Figure 4 The brazed structure diagram of the casting after brazing is obtained for Comparative Example 2;

[0048] Figure 5 The surface crack condition diagram of the casting obtained for comparative example 3;

[0049] Figure 6 The brazed structure diagram of the casting after brazing is obtained for Comparative Example 4;

[0050] Figure 7 The cross-sectional microstructure diagram of the casting obtained in Example 3 after 500 hours of corrosion test after brazing;

[0051] Figure 8 For comparative example 2, a cross-sectional metallographic structure diagram of the casting was obtained after a corrosion test of 500 hours after brazing. DETAILED DESCRIPTION

[0052] The present invention achieves the enhancement and strengthening of advantageous properties and the reduction or even avoidance of inferior properties by providing a new multi-element eutectic alloy system. Based on the multiple problems existing in the development process of existing brazed cast aluminum alloys, a feasible practical alloy system is provided.

[0053] The present invention provides a multi-element eutectic cast aluminum alloy suitable for brazing. The cast aluminum alloy comprises, in terms of weight percentage: Mn: 1.0wt.%-2.0wt.%; Ni: 1.5wt.%-3.5wt.%; Fe: 0.05wt.%-0.5wt.%; RE: 0.05wt.%-5.5wt.%; X: 0.05wt.%-0.4wt.%, wherein X is Ti and / or Cr, and RE is Ce and / or La.

[0054] During the solidification process of the multi-element eutectic alloy system, a variety of eutectic reactions will occur to form a structure composed of primary α-Al and multi-element eutectic structures. Furthermore, the multi-element eutectic structure includes a eutectic second phase with a melting point of more than 620°C, and the eutectic second phase includes a eutectic α-Al phase, an Al6M phase, an Al 11 RE3 phase, Al8REM4 phase, Al 23 Three or more of RE4M6 phase, Al3M phase, Al9M2 phase, wherein M is one or a combination of two or a combination of three of Mn, Fe, Ni, and the shape of the eutectic second phase is blocky, lamellar, fibrous, short rod or worm-like.

[0055] Through the design of the matching system, the area of ​​the multi-element eutectic structure in the present invention accounts for 30% to 60% of the total area of ​​the alloy structure. In a specific case, the area of ​​the multi-element eutectic structure accounts for more than 31% of the total area of ​​the alloy structure. Based on such a high fraction of eutectic content, the solidification range value of the cast aluminum alloy in the present invention is less than 30°C, which is beneficial to reduce the tendency of hot cracking, increase shrinkage compensation, and prevent cracking during casting.

[0056] In some embodiments, the cast aluminum alloy or aluminum alloy casting described in the present invention may have the element composition shown in Table 1.

[0057] Table 1

[0058]

[0059] The method for preparing a cast aluminum alloy or an aluminum alloy casting comprises:

[0060] (a) Prepare the raw materials according to the composition requirements. First, put the industrial pure Al ingot, Al-Mn master alloy or Mn agent, Al-Fe master alloy or Fe agent, Al-Ni master alloy or Ni agent, Al-RE master alloy, etc. into the melting furnace, completely melt them at 780-800°C, reduce the temperature of the aluminum liquid to 740-760°C, and keep it warm for 15-60 minutes;

[0061] (b) adding Al-X master alloy according to the designed amount, and after it is completely melted, heat preservation treatment is performed;

[0062] (c) adding a refining agent and a grain refiner, refining and degassing at 740-750°C, and after the degassing is completed, standing for 10-30 minutes before slagging;

[0063] (d) If the molten material after slag removal is cooled, a cast aluminum alloy can be obtained; if the molten material after slag removal is cast, an aluminum alloy casting can be obtained.

[0064] Furthermore, the temperature of the molten metal before casting can be controlled at 700-750°C, and the casting can be carried out by metal mold gravity casting or low-pressure casting or high-pressure casting or extrusion casting process, and the mold temperature is controlled at 150-400°C, that is, the expected casting effect can be achieved within this wider temperature operation window.

[0065] Furthermore, since the operating temperature window of the multi-element eutectic cast aluminum alloy suitable for brazing of the present invention is relatively wide, it is preferred that the metal melt temperature before casting can be controlled below 725°C to reduce the requirements for equipment (the higher the melt temperature, the higher the tolerance requirements for the equipment).

[0066] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0067] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0068] In the following, in order to facilitate the testing of the brazing and other properties of the cast aluminum alloy, the aluminum alloy casting is directly cast into an aluminum alloy casting during the aluminum alloy forming process for testing. The difference between the two is that the aluminum alloy is formed by directly cooling the melt after the refinement of each component, while the aluminum alloy casting is formed by pouring the melt after the refinement of each component into a preset shape and then cooling it. Therefore, the performance of the aluminum alloy casting can reflect the performance of the cast aluminum alloy.

[0069] In the art, the pre-designed quantities of aluminum alloy castings during preparation may have certain errors from the actual test values ​​at a later stage. The following description is based on the test values ​​after casting is completed, and the content of each metal is measured by a direct reading spectrometer.

[0070] Example 1

[0071] This example provides a multi-element eutectic cast aluminum alloy suitable for brazing and a preparation method thereof. The preparation method of the multi-element eutectic cast aluminum alloy suitable for brazing comprises:

[0072] (1) placing industrial pure Al ingots, Al-Mn master alloys, Al-Fe master alloys, Al-Ni master alloys, and Al-Ce master alloys in a melting furnace and heating them to 790±10°C according to the designed amount; after the raw materials in the melting furnace are melted, cooling the melting furnace to 740±10°C and keeping the temperature for 40 minutes;

[0073] (2) Add Al-Ti master alloy and Al-Cr master alloy into the melting furnace according to the designed amount, melt them completely, and keep them at 740±10℃ for 10min;

[0074] (3) adding 2‰ of the mass of the melt into the smelting furnace, respectively, a solid refining agent (specifically Foseco Coveral78) and 5.0‰ of a refiner (specifically Shenzhen Xinxing Al-Ti5-B refiner), and degassing the molten metal by stirring with a rotating rotor at 745±5°C for 20 minutes. After the degassing is completed, the molten metal is allowed to stand for 20 minutes and then slag is removed to obtain a refined metal melt;

[0075] (4) When the temperature of the molten metal is 720±5°C, extrusion casting is performed. First, the molten metal is slowly pressed into a casting mold preheated at 175±10°C and maintained at a pressure of 100±10 MPa for 40 seconds, and then a casting is obtained;

[0076] The casting components and their weight percentages obtained in this example are: Mn: 1.5wt.%; Ni: 3.2wt.%; Fe: 0.3wt.%; Ce: 5.2wt.%; La: 0.0002wt.%; Ti: 0.12wt.%; Cr: 0.12wt.%; the rest are Al and inevitable impurities, among which Si: 0.07wt.%; Mg: 0.0022wt.%; Cu: 0.008wt.%, Zn: 0.005wt.%. La is not added in this example, and La should come from trace components contained in other raw materials.

[0077] Example 2

[0078] The method is basically the same as Example 1, except that the designed amounts of the component formulas are different.

[0079] The casting components and their weight percentages obtained in this example are: Mn: 1.6wt.%; Ni: 1.9wt.%; Fe: 0.18wt.%; Ce: 5.1wt.%; La: 0.0008wt.%; Ti: 0.08wt.%; Cr: 0.2wt.%; the rest are Al and inevitable impurities, among which Si: 0.09wt.%; Mg: 0.0012wt.%; Cu: 0.006wt.%; Zn: 0.009wt.%. La is not added in this example, and La should come from trace components contained in other raw materials.

[0080] Example 3

[0081] The method is basically the same as Example 1, except that the designed amounts of the component formulas are different.

[0082] The casting components and their weight percentages obtained in this example are: Mn: 1.6wt.%; Ni: 2.0wt.%; Fe: 0.2wt.%; Ce: 2.9wt.%; La: 0.0005wt.%; Ti: 0.09wt.%; Cr: 0.12wt.%; the rest are Al and inevitable impurities, among which Si: 0.08wt.%; Mg: 0.0015wt.%; Cu: 0.007wt.%, Zn: 0.007wt.%. La is not added in this example, and La should come from trace components contained in other raw materials.

[0083] Example 4

[0084] The method is basically the same as Example 1, except that the designed amounts of the component formulas are different.

[0085] The casting components and their weight percentages obtained in this example are: Mn: 1.7wt.%; Ni: 2.0wt.%; Fe: 0.17wt.%; Ce: 1.2wt.%; La: 0.0004wt.%; Ti: 0.09wt.%; Cr: 0.11wt.%; the rest are Al and inevitable impurities, among which Si: 0.05wt.%; Mg: 0.003wt.%; Cu: 0.003wt.%, Zn: 0.005wt.%. La is not added in this example, and La should come from trace components contained in other raw materials.

[0086] Example 5

[0087] The method is basically the same as Example 1, except that: the designed amounts of the component formulas are different;

[0088] (1) According to the designed amount, industrial pure Al ingots, Al-Mn master alloys, Al-Fe master alloys, Al-Ni master alloys, and Al-La master alloys are placed in a melting furnace and heated to 790±10°C. After the raw materials in the melting furnace are melted, the melting furnace is cooled to 740±10°C and kept warm for 40 minutes.

[0089] The casting components and their weight percentages obtained in this example are: Mn: 1.6wt.%; Ni: 1.9wt.%; Fe: 0.20wt.%; Ce: 0.0002wt.%; La: 5.1wt.%; Ti: 0.1wt.%; Cr: 0.15wt.%; the rest is Al and inevitable impurities, among which Si: 0.06wt.%; Mg: 0.002wt.%; Cu: 0.005wt.%, Zn: 0.006wt.%. Ce is not added in this example, and Ce should come from trace components contained in other raw materials.

[0090] Example 6

[0091] The method is basically the same as Example 1, except that the designed amounts of the component formulas are different.

[0092] The casting components and their weight percentages obtained in this example are: Mn: 1.5wt.%; Ni: 2.0wt.%; Fe: 0.15wt.%; Ce: 3.0wt.%; La: 0.0002wt.%; Ti: 0.08wt.%; Cr: 0.001wt.%; the rest are Al and inevitable impurities, among which Si: 0.07wt.%; Mg: 0.002wt.%; Cu: 0.004wt.%; Zn: 0.004wt.%. In this example, La and Cr are not added, and La and Cr should come from trace components contained in other raw materials.

[0093] Comparative Example 1

[0094] The method is basically the same as Example 3, except that no Al-Ni master alloy is added.

[0095] The casting components and their weight percentages obtained in this comparative example are: Mn: 1.6wt.%; Ni: 0.008wt.%; Fe: 0.2wt.%; Ce: 2.9wt.%; La: 0.0004wt.%; Ti: 0.08wt.%; Cr: 0.12wt.%; the rest are Al and inevitable impurities, among which Si: 0.05wt.%; Mg: 0.005wt.%; Cu: 0.006wt.%; Zn: 0.007wt.%. In this example, Ni and La are not added, and Ni and La should come from trace components contained in other raw materials.

[0096] Comparative Example 2

[0097] The method is basically the same as Example 3, except that no Al-Ce and Al-La master alloys are added.

[0098] The casting components and their weight percentages obtained in this comparative example are: Mn: 1.6wt.%; Ni: 2.0wt.%; Fe: 0.19wt.%; Ce: 0.0004wt.%; La: 0.0005wt.%; Ti: 0.08wt.%; Cr: 0.11wt.%; the rest are Al and inevitable impurities, among which Si: 0.09wt.%; Mg: 0.002wt.%; Cu: 0.002wt.%; Zn: 0.002wt.%. Ce and La are not added in this example, and Ce and La should come from trace components contained in other raw materials.

[0099] Comparative Example 3

[0100] It is basically the same as Example 3, except that Mg is added.

[0101] The casting components and their weight percentages obtained in this comparative example are: Mn: 1.6wt.%; Ni: 2.1wt.%; Fe: 0.19wt.%; Ce: 2.8wt.%; La: 0.0006wt.%; Ti: 0.09wt.%; Cr: 0.13wt.%; Mg: 0.5wt.%; the rest are Al and unavoidable impurities, among which Si: 0.09wt.%; Cu: 0.002wt.%; Zn: 0.002wt.%. La is not added in this example, and La should come from trace components contained in other raw materials.

[0102] Comparative Example 4

[0103] The method is basically the same as Example 3, except that no Al-Ni, Al-Ce and Al-La master alloys are added.

[0104] The casting components and their weight percentages obtained in this comparative example are: Mn: 1.6wt.%; Ni: 0.0004wt.%; Fe: 0.21wt.%; Ce: 0.0002wt.%; La: 0.0003wt.%; Ti: 0.09wt.%; Cr: 0.12wt.%; the rest are Al and inevitable impurities, among which Si: 0.07wt.%; Mg: 0.003wt.%; Cu: 0.004wt.%; Zn: 0.002wt.%. In this example, no Ni, Ce and La are added, and Ni, Ce and La should come from trace components contained in other raw materials.

[0105] Performance Testing

[0106] (1) The Scheil solidification curve corresponding to the alloy composition in Example 3 was calculated using Thermo-Calc thermodynamic calculation software, as shown in FIG. Figure 1 As shown in the figure, it can be seen that in the early stage of solidification, the primary α-Al phase is first precipitated in the melt, and then the alloy undergoes multiple eutectic reactions to generate eutectic α-Al, Al6Mn, Al 23 A variety of second phases including Ce4Ni6, Al3Ni, Al9FeNi, etc. These second phases with high melting point and high stability can form a three-dimensional continuous network structure, effectively achieving the strengthening and high-temperature stability of aluminum alloys. At the same time, it can be seen that under this alloy composition, the temperature of ending solidification is 635°C, which is significantly higher than the 590-620°C required for general brazing, ensuring the stability of the organization during brazing. In addition, the solidification range of the alloy is less than 15°C, and it has a high molar fraction of eutectic content, which is conducive to reducing the tendency of hot cracking, increasing shrinkage compensation, and preventing cracking during casting.

[0107] The scanning photo of the casting obtained in Example 3 at 500 times is as follows Figure 2 As shown in the figure, the microstructure of the cast aluminum alloy provided in Example 3 is composed of primary α-Al and eutectic structure, wherein the eutectic structure is composed of eutectic α-Al phase, Al6 (Fe, Mn, Ni) phase, Al3 (Ni, Mn), AlCeMn phase, Al 11 Ce3 phase and other eutectic second phases. These eutectic second phases have different shapes, including block, lamellar, fibrous, short rod and worm. Therefore, through the above alloy composition design and process control, a multi-element eutectic structure was successfully obtained. Based on the metallographic photos, it can be calculated that the area fraction of the eutectic structure in the structure of Example 3 is about 37%, which ensures that the material has good casting properties and mechanical properties before and after brazing.

[0108] The scanning photos of the casting of Example 3 after brazing are as follows Figure 3 As shown. Among them, the brazing conditions are 605℃ and 20min. As can be seen from the figure, after brazing, there is no obvious overburned area in the organization, the original eutectic organization is spheroidized, and the edge becomes "blunt", which helps to improve the elongation of the material. In general, the eutectic organization does not change much before and after brazing, which ensures the stability of the mechanical properties before and after brazing. In addition, a certain number of dispersed particles are precipitated in the α-Al matrix during the brazing process. These dispersed particles include Al6Mn and Al3X dispersed particles formed by Ti and the like. The presence of these dispersed particles is conducive to improving the post-weld strength and avoiding a significant reduction in strength due to brazing.

[0109] The area fraction of eutectic structure in the aluminum alloy obtained in the above examples and comparative examples, as well as the room temperature mechanical properties in the cast and brazed states are shown in Table 2. The area fraction of eutectic structure was calculated using metallographic photographs, and the room temperature mechanical properties of the aluminum alloy castings before and after brazing were tested using an electronic universal testing machine.

[0110] Table 2

[0111]

[0112] The test standard for mechanical properties in cast state and mechanical properties in brazed state is GB / T228.1-2010.

[0113] As can be seen from Table 2, in Example 1, by adding Mn, Ni, Fe, Ce / La, X and other elements at the same time, the eutectic structure content can be increased, which can effectively improve the mechanical properties of the alloy before and after brazing. Comparing the tensile properties of Examples 2 to 4, it can be seen that as the Ce content increases from 1.2wt.% to 5.1wt.%, the eutectic structure content in the alloy increases from 31% to 44%, the strength of the alloy gradually increases, and the elongation decreases slightly. Comparing Example 2 and Example 5, adding La and adding Ce have similar results. It can also be seen from Example 6 that the addition of elements such as Cr will also have a certain effect on the improvement of mechanical properties. In addition, by comparing the mechanical properties before and after brazing, it can be seen that after brazing, the strength of all alloys is slightly reduced and the elongation is slightly improved, which is also due to the good high temperature stability of the above-mentioned alloys and the precipitation of dispersed phases.

[0114] In Comparative Example 1, since no Ni element is added, there is no Ni-containing eutectic phase in the matrix, while in the alloy system of the present invention, the Ni-containing eutectic phase has a fine fiber structure, which is very helpful for improving the strength of the alloy. Therefore, compared with Example 3, the eutectic structure area fraction of Comparative Example 1 is lower, and the strength in the cast and brazed state is also lower, with the tensile strength in the cast state being only 149 MPa and the yield strength being only 69 MPa.

[0115] The metallographic structure photograph of the casting obtained in Comparative Example 2 after brazing treatment at a magnification of 500 times is as follows Figure 4 As shown. Figure 4 It can be seen that in Comparative Example 2, since Ce and La elements are not added, the eutectic structure content in the alloy system of the present invention is only 25%, which leads to its tensile strength being lower than 165 MPa and its yield strength being lower than 76 MPa.

[0116] Figure 5 The micro cracks on the surface of the casting obtained in Comparative Example 3. For castings, cracks are a type of defect that cannot be allowed to exist. Under the same process conditions, in the alloy system of the present invention, the addition of Mg will increase the hot cracking tendency and reduce the yield rate of the product.

[0117] The metallographic structure photograph of the casting obtained in Comparative Example 4 after brazing treatment at a magnification of 500 times is as follows Figure 6 As shown. Figure 6 It can be seen that without adding elements such as Ni, Fe, Ce / La, etc., in the alloy system of the present invention, there is only a small amount of Al6Mn eutectic second phase on the grain boundary, which also causes its strength to be significantly lower than that of other alloys.

[0118] In addition, an acetic acid cyclic salt spray test was carried out in accordance with the ASTM-85A3 standard, and the corrosion resistance of Example 3 and Comparative Example 2 was compared. It can be seen that due to the relatively stringent corrosion standard, both alloys have undergone obvious corrosion. However, in comparison, the corrosion depth of the alloy of Example 3 (618μm) is significantly less than the corrosion depth of the alloy of Comparative Example 2 (1108μm). The main reasons are speculated as follows: the potential of the Ni-containing phase is significantly higher than that of the matrix, which easily leads to the priority of the matrix near it, and then the corrosion quickly expands inward, while the potential of the Ce / La-containing phase is slightly lower than that of the matrix, and it is alternately distributed with the Ni-containing phase on the grain boundary, which is conducive to slowing down the corrosion process. Therefore, after adding the RE element, the corrosion resistance of the alloy is improved.

[0119] In summary, the Al-Mn-Ni-Fe-RE-X casting alloy provided by the present invention has a multi-element eutectic structure with a high melting point and a high area fraction, and has good casting performance, good brazing performance, excellent mechanical properties and corrosion resistance, and can meet the needs of high-temperature brazing castings; further, the room temperature tensile strength of the above-mentioned cast aluminum alloy in the cast state is above 170MPa, and the elongation is greater than or equal to 8%, and the room temperature tensile strength in the brazed state is above 165MPa, and the elongation is greater than or equal to 12%. Therefore, the above-mentioned cast aluminum alloy can meet the needs of high-temperature brazing castings in the fields of electronic equipment, new energy vehicles, etc.

[0120] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0121] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A multicomponent eutectic cast aluminum alloy suitable for brazing, characterized in that: The cast aluminum alloy comprises Al, Mn, Ni, Fe, X and RE, and unavoidable impurities; Wherein, X is Ti and / or Cr, RE is Ce and / or La; During the solidification process, a variety of eutectic reactions occur, forming an organizational structure composed of primary α-Al and multi-element eutectic structures; The multi-element eutectic structure includes a eutectic second phase, and the eutectic second phase includes a eutectic α-Al phase, an Al6M phase, an Al 11 RE3 phase, Al8REM4 phase, Al 23 Three or more of RE4M6 phase, Al3M phase, Al9M2 phase, wherein M is one or a combination of two or a combination of three of Mn, Fe, and Ni; The melting point of the eutectic second phase is above 620°C; The unavoidable impurities include Mg, Cu, Si or Zn, and in terms of weight percentage, the Si content is controlled to be ≤0.2wt.%, the Mg content is ≤0.1wt.%, the Cu content is ≤0.1wt.%, the Zn content is ≤0.1wt.%, and the total impurity content is less than or equal to 0.3wt.%.

2. The multicomponent eutectic cast aluminum alloy suitable for brazing according to claim 1, characterized in that: The mass ratio of Ni to RE is 0.3-3.5:

1.

3. The multicomponent eutectic cast aluminum alloy suitable for brazing according to claim 2, characterized in that: The mass ratio of Ni to RE is 0.35-2.0:

1.

4. The multicomponent eutectic cast aluminum alloy suitable for brazing according to claim 1, characterized in that: Measured in weight percentage, the cast aluminum alloy includes: Mn: 1.0wt.% to 2.0wt.%; Ni: 1.5wt.% to 3.5wt.%; Fe: 0.05wt.% to 0.5wt.%; RE: 0.05wt.% to 5.5wt.%; X: 0.05wt.% to 0.4wt.%.

5. The multicomponent eutectic cast aluminum alloy suitable for brazing according to claim 4, characterized in that: Measured in weight percentage, the cast aluminum alloy includes: Mn: 1.2wt.% to 1.8wt.%; Ni: 1.8wt.% to 3.5wt.%; Fe: 0.1wt.% to 0.4wt.%; RE: 0.5wt.% to 5.5wt.%; X: 0.1wt.% to 0.35wt.%.

6. The multicomponent eutectic cast aluminum alloy suitable for brazing according to claim 5, characterized in that: Measured in weight percentage, the cast aluminum alloy includes: Mn: 1.4wt.% to 1.8wt.%; Ni: 1.9wt.% to 3.3wt.%; Fe: 0.15wt.% to 0.35wt.%; RE: 1.0wt.% to 5.3wt.%; X: 0.15wt.% to 0.30wt.%.

7. The multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 6, characterized in that: The area of ​​the multi-element eutectic structure accounts for 30% to 60% of the total area of ​​the alloy structure; and / or the shape of the eutectic second phase is block-shaped, lamellar, fibrous, short rod-shaped or worm-shaped.

8. The multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 6, characterized in that: When RE is Ce, the multi-element eutectic structure at least includes eutectic α-Al phase, Al6 (Fe, Mn, Ni) phase, Al3 (Ni, Mn), AlCeMn phase, Al 11 Ce3 phase.

9. The multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 6, characterized in that: The solidification interval value of the cast aluminum alloy is less than 30°C; and / or the melt temperature of the cast aluminum alloy before casting can be less than or equal to 725°C.

10. The multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 6, characterized in that: In the cast state, the cast aluminum alloy has a tensile strength of more than 170 MPa, a yield strength of more than 85 MPa, and an elongation of more than 8% at room temperature.

11. The multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 6, characterized in that: After brazing, the cast aluminum alloy has a tensile strength of more than 165 MPa, a yield strength of more than 80 MPa, and an elongation of more than 12% at room temperature.

12. A method for preparing a multicomponent eutectic cast aluminum alloy suitable for brazing according to any one of claims 1 to 11, characterized in that: The preparation method comprises: Weigh each component according to the formula amount, melt it, and obtain a melt; adding a refining aid to the melt to obtain a metal melt after refining; The metal melt is cooled to obtain the cast aluminum alloy.

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