Composite microalloyed aluminum alloy and solidification forming preparation process thereof

Abstract

The invention discloses a composite microalloyed aluminum alloy which is prepared from the following components in percentage by mass: 0.7%-1.3% of Si, 0.6%-1.2% of Mg, 0.4%-1.0% of Mn, 0.2%-0.6% of microalloy elements and the balance of Al, wherein the microalloy elements are Sc and Cr, or the microalloy elements are Sc, Cr and Zr. By adding microalloy elements, the aluminum alloy obtained in the invention has excellent mechanical properties at room temperature and high temperature, the invention further discloses a solidification forming preparation process of the aluminum alloy, uniform dispersion of the elements is further promoted through ultrasonic-assisted vibration, and the overall performance is improved.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum alloys, and in particular to a composite microalloyed aluminum alloy and a solidification forming preparation process thereof. Background Art

[0002] In modern manufacturing, Al-Si-Mg-Mn alloy has been widely used in the manufacturing of various complex components due to its low density, high specific strength and excellent processing performance. With the continuous advancement of manufacturing technology, the squeeze casting process combines the advantages of traditional casting and forging processes and gradually becomes a key technical means for the production of aluminum alloy components. This process can not only achieve near-net forming of complex-shaped components, but also effectively improve the structural density and comprehensive mechanical properties of the components.

[0003] However, with the rapid development of the new energy vehicle industry, higher requirements are placed on the service performance of chassis and body structural parts. The existing Al-Si-Mg-Mn alloys can no longer meet the needs of high-performance application scenarios in terms of fatigue resistance, deformation resistance, and high-temperature service performance. Specifically, the traditional casting process will inevitably produce microscopic hole defects, which are very likely to cause stress concentration; at the same time, the existing Al-Si-Mg-Mn alloys are difficult to achieve the target requirements of 300MPa yield strength and 8% elongation at the same time; in addition, the non-equilibrium segregation of elements such as Mg at the grain boundaries in the alloy system will accelerate grain boundary sliding under high temperature conditions, thereby making the high-temperature mechanical properties of the alloy poor. Based on the above status quo, it is urgent to develop an aluminum alloy material with better performance and its preparation process. Summary of the invention

[0004] The purpose of the present application is to provide a composite micro-alloyed aluminum alloy and its solidification forming preparation process to solve the shortcomings of the existing Al-Si-Mg-Mn alloy and meet the growing demand for high-performance applications.

[0005] The embodiments of the present application can be implemented through the following technical solutions:

[0006] A composite microalloyed aluminum alloy, comprising the following components by mass percentage:

[0007] Si 0.7%-1.3%,

[0008] Mg 0.6%-1.2%,

[0009] Mn 0.4%-1.0%,

[0010] Micro alloying elements 0.2%-0.6%,

[0011] The balance is Al;

[0012] Wherein, the micro-alloying elements are Sc and Cr, or the micro-alloying elements are Sc, Cr and Zr.

[0013] Preferably, the alloy is composed of the following components in percentage by mass: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc 0.1%-0.5%, Cr 0.1%, and the balance is Al.

[0014] Preferably, the alloy is composed of the following components in percentage by mass: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance is Al.

[0015] A solidification forming preparation process of the above-mentioned composite microalloyed aluminum alloy comprises the following steps:

[0016] S1, complete the batching according to the designed alloy composition;

[0017] S2, placing the ingredients in a heating furnace until they are completely melted and mechanically stirred;

[0018] S3, applying ultrasonic vibration to the completely melted molten alloy;

[0019] S4, refining, slagging, temperature-controlled standing, and obtaining an aluminum alloy solution;

[0020] S5, pouring the metal solution after standing into a preheated mold, extrusion casting and pressure holding, and cooling to obtain an aluminum alloy casting;

[0021] S6, subjecting the aluminum alloy casting formed by extrusion casting to solid solution quenching treatment and aging treatment.

[0022] Further, the S2 comprises the following steps:

[0023] S21, placing Al, Si, Mg, and Mn raw materials in a heating furnace and maintaining the temperature at 750-780° C. until they are completely melted;

[0024] S22, maintaining the temperature at 750-780°C, and continuously adding Al-Sc, Al-Zr and Al-Cr master alloy raw materials until they are completely melted.

[0025] Furthermore, the specific parameters of applying ultrasonic vibration in S3 are: ultrasonic power of 1000-2000 W, amplitude of 0.1-100 μm, ultrasonic time of 100-1000 s, and ultrasonic frequency of 10-20 kHz.

[0026] Furthermore, the specific process of S4 includes: adding a refining agent to the completely molten metal solution for refining, maintaining the temperature at 750-780°C during refining, skimming off the slag after refining, and controlling the temperature to maintain at 750-780°C for 10 minutes.

[0027] Furthermore, the refining agent is C2Cl6, and the amount of the refining agent added is 1wt% of the total mass of the metal solution.

[0028] Furthermore, the specific process conditions in S5 are: the mold preheating temperature is 280-300° C., the pressure of the extrusion casting is 150-200 MPa, and the pressure holding condition is to maintain the pressure at 100-200 MPa for 30-120 seconds.

[0029] Furthermore, the solution quenching treatment in S6 is to keep the aluminum alloy casting at a temperature of 520-540°C for 10-12 hours and then cool it to room temperature; the aging treatment is to keep the aluminum alloy casting after the solution quenching treatment at a temperature of 170-190°C for 11-13 hours and then cool it to room temperature.

[0030] The embodiments of the present application provide a composite microalloyed aluminum alloy and a solidification forming preparation process thereof, which have at least the following beneficial effects:

[0031] The present invention provides a novel composite microalloyed aluminum alloy by adding trace amounts of Sc, Zr and Cr to an Al-Si-Mg-Mn alloy. 1-x Zr x ) second phase particles and Al-(FeMnCr)Si phase, to achieve fine grain strengthening and dispersion strengthening, combined with further improvement of the preparation process, it is possible to prepare aluminum alloy components with low cost, dense organization, excellent comprehensive mechanical properties and which still maintain good mechanical properties and structural stability when serving at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The metallographic microstructures of the alloys of different embodiments and comparative examples are as follows: (a) comparative example 1, (b) embodiment 1, (c) embodiment 2, (d) embodiment 3, (e) embodiment 4, and (f) embodiment 5; DETAILED DESCRIPTION

[0033] The present application is further described below based on preferred embodiments and with reference to the accompanying drawings. Various raw materials used in the present application are commercially available products. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0034] The present application provides a composite microalloyed aluminum alloy, which is composed of the following components in terms of mass percentage:

[0035] Si 0.7%-1.3%,

[0036] Mg 0.6%-1.2%,

[0037] Mn 0.4%-1.0%,

[0038] Micro alloying elements 0.2%-0.6%,

[0039] The balance is Al;

[0040] Wherein, the micro-alloying elements are Sc and Cr, or the micro-alloying elements are Sc, Cr and Zr.

[0041] In some preferred embodiments, the composite microalloyed aluminum alloy of the present application is composed of the following components by mass percentage: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc 0.1%-0.5%, Cr 0.1%, and the balance is Al;

[0042] Among them, the rare earth element Sc is added as a microalloying element to improve the mechanical properties, welding properties, creep resistance and corrosion resistance of the aluminum-based alloy; a large number of Al3Sc particles are formed during the solidification process, and the lattice mismatch between the Al3Sc phase and the α-Al phase is 1.0% (<5%), that is, Al3Sc can serve as a heterogeneous nucleation material for α-Al to promote grain refinement. An appropriate amount of Al3Sc precipitated phase can refine the grains and improve the strength of the alloy, but too high a Sc content will cause Al3Sc particles to accumulate too much at the grain boundaries or within the grains, thereby affecting the movement of the grain boundaries, reducing the plasticity of the alloy under high temperature or stress, and increasing brittleness; in addition, a higher Sc content may affect the heat treatment process of the alloy, especially during the aging treatment process, too much Sc may change the distribution and morphology of the precipitated phase, thereby affecting the strength and ductility of the alloy;

[0043] Preferably, the content of Sc is 0.1%-0.5%, and more preferably, the content of Sc is 0.3%-0.5%.

[0044] By adding Cr, it can interact with Mn to form Al-(FeMnCr)Si phase, which is distributed around the eutectic Si and helps to transform the coarse eutectic Si particles into a fine fibrous structure, thereby further improving the mechanical properties of the alloy; in addition, the Al-(FeMnCr)Si phase has higher stability than the Mg2Si phase in a high temperature environment, which enables the alloy to maintain good mechanical properties and structural stability during high-temperature service.

[0045] Although adding the rare earth element Sc can effectively improve the mechanical properties of aluminum alloys, the cost of Sc is very high. Therefore, the present application further introduces Zr to partially replace Sc, which can reduce the cost and reduce the amount of rare earth element Sc while overcoming the shortcomings of the existing Al-Si-Mg-Mn alloy performance; in some preferred embodiments, the composite micro-alloyed aluminum alloy of the present application is composed of the following components in mass percentage: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc0.3%, Zr 0.2%, Cr 0.1%, and the balance is Al.

[0046] Sc and Zr effectively refine the grains through the heterogeneous nucleation mechanism and interact with matrix elements to form stable compounds or solid solutions, which significantly inhibit grain boundary migration and recrystallization. Zr and Sc form primary Al3(Sc) with L12 structure during solidification. 1-x Zr x ) phase, which can improve the strength of the alloy through the Orowan strengthening mechanism, and this phase has higher stability in high temperature environment; in addition, Al3(Sc,Zr) phase will precipitate during the solidification process, and because the lattice mismatch between the Al3Zr phase and the α-Al phase is about 0.5%, the partial replacement of Sc by Zr can also reduce the lattice mismatch with the α-Al phase, thereby improving the nucleation efficiency and further promoting grain refinement.

[0047] In the aluminum alloy of the present application, in addition to the above elements, there is also an impurity element Fe, which tends to accumulate at the solid-liquid interface during the solidification process to form a coarse, hard, brittle, and highly thermally shrinkable AlFeMnSi phase, which belongs to the impurity phase and will cause significant fragmentation of the matrix, increase hot brittleness, and make the casting more prone to cracking; in addition, the iron-rich impurity phase, as a stress concentration point, will also reduce the strength and ductility of the alloy. The present application can significantly change the morphology of the iron-rich impurity phase by adding the above-mentioned microalloying elements, so that it is transformed from a needle-like or coarse skeleton-like structure to a small, broken, spherical structure with blunted edges. This morphological change effectively alleviates the negative impact of the iron-rich impurity phase, avoids stress concentration during the stretching process, and thus improves the strength and ductility of the alloy.

[0048] In some preferred embodiments, the content of impurity Fe element in the composite microalloyed aluminum alloy of the present application is ≤0.25%.

[0049] The present application also provides a solidification forming preparation process of the above-mentioned microalloyed aluminum alloy, which comprises the following steps:

[0050] S1, weigh Al-Sc, Al-Zr and Al-Cr master alloy raw materials of Al, Si, Mg and Mn according to the designed alloy composition;

[0051] S2, placing the ingredients in S1 in a heating furnace to melt at a melting temperature of 750-780°C;

[0052] Furthermore, the S2 specifically includes the following steps:

[0053] S21, placing Al, Si, Mg, and Mn in a heating furnace until they are completely melted;

[0054] S22, adding Al-Sc, Al-Zr and Al-Cr master alloys to the completely melted metal solution in S21 until the metal solution is completely melted, and stirring;

[0055] In some specific embodiments, the heating furnace is a pit-type heating furnace;

[0056] In some specific embodiments, the stirring speed in S22 is 200-300 rpm, and the stirring time is 30 min;

[0057] S3, inserting an ultrasonic probe into the molten alloy to apply ultrasonic vibration; specifically, the ultrasonic power is 1000-2000W, the amplitude is 0.1-100μm, the ultrasonic time is 100-1000s, and the ultrasonic frequency is 10-20kHz; applying ultrasonic vibration can effectively break up the agglomerated particles in the alloy, promote the uniform distribution of different components, and thus improve the microstructure and performance of the alloy;

[0058] S4, refining, slagging, temperature-controlled standing, to obtain an aluminum alloy solution; specifically, adding a refining agent to the completely molten metal solution for refining, the temperature during refining is maintained at 750-780°C; specifically, the refining agent is C2Cl6, and the amount of the refining agent added is 1wt% of the total mass of the metal solution;

[0059] After refining, the slag is removed and the molten metal is placed under temperature control; specifically, the temperature is maintained at 750-780°C and the placement time is 10 minutes;

[0060] S5, pouring the metal solution after standing into the preheated mold, extrusion casting and holding the pressure, and taking out the casting after cooling; in some preferred embodiments, the mold preheating temperature is 280-300°C, and the appropriate mold preheating temperature is used to improve the fluidity of the metal solution, so that it is easier to fill the mold cavity and reduce the occurrence of insufficient filling; in some preferred embodiments, the pressure of extrusion casting is 150-200Mpa, and the pressure is applied to provide comprehensive liquid feeding and plastic deformation to offset the tensile stress caused by solidification shrinkage, avoid the generation of shrinkage gaps and microcracks, and reduce bubbles in the casting; in some preferred embodiments, the holding pressure condition is to maintain a pressure of 100-200MPa for 30-120s;

[0061] S6, subjecting the aluminum alloy casting formed by extrusion casting to solid solution quenching treatment and aging treatment; specifically, the solid solution quenching treatment is to keep the aluminum alloy casting at a temperature of 520-540°C for 10-12h, and then water-cool it to room temperature; the aging treatment is to keep the aluminum alloy casting after the solid solution quenching treatment at a temperature of 170-190°C for 11-13h, and then cool it to room temperature with the furnace.

[0062] Example 1

[0063] This embodiment prepares an Al-Si-Mg-Mn aluminum alloy using Sc and Cr composite microalloying, which is specifically implemented according to the following steps:

[0064] Prepare the materials by mass percentage: Si 0.7%, Mg 0.6%, Mn 0.4%, Sc 0.1%, Cr 0.1%, and the balance Al, add Al, Si, Mg, and Mn in the raw materials into a pit-type heating furnace, control the temperature in the furnace at 750-780°C, melt the above metals completely, then add Al-Sc and Al-Cr master alloy in the raw materials, and after they are completely melted, use a mechanical stirring device to stir at a speed of 200-300rpm for 30 minutes;

[0065] Inserting an ultrasonic probe into the molten alloy, applying ultrasonic vibration, the ultrasonic power is set to 1000W to 2000W, the amplitude range is 0.1μm to 100μm, the application time is 100 seconds to 1000 seconds, and the ultrasonic frequency is 10kHz to 20kHz;

[0066] Add C2Cl6 to the above molten alloy for refining, the amount of refining agent added is 1wt% of the total mass of the metal solution, and slag treatment is performed after the refining is completed; the refined metal solution is allowed to stand for 10 minutes, and the standing temperature is maintained at 750-780°C;

[0067] The alloy solution after standing is poured into a mold preheated to 300°C, and a four-column hydraulic press is used to apply a pressure of 150Mpa for extrusion casting. Then, the pressure is maintained at 150Mpa for 60s, and the casting is taken out after cooling;

[0068] The aluminum alloy casting after extrusion casting is heated to 520℃-540℃ for solution treatment, kept at this temperature for 10-12 hours, then taken out of the furnace and quickly quenched with water to room temperature;

[0069] The quenched aluminum alloy casting is heated to 170℃-190℃, kept warm for 11-13 hours for aging treatment, and naturally cooled to room temperature after being taken out of the furnace.

[0070] Example 2

[0071] In this embodiment 2, a Sc and Cr composite microalloyed Al-Si-Mg-Mn aluminum alloy is prepared according to the method of embodiment 1, and the difference from embodiment 1 is that:

[0072] The materials are prepared according to mass percentage: Si 1.0%, Mg 0.9%, Mn 0.7%, Sc 0.3%, Cr 0.1% and the balance is Al.

[0073] Example 3

[0074] In this embodiment 3, a Sc and Cr composite microalloyed Al-Si-Mg-Mn aluminum alloy is prepared according to the method of embodiment 1, and the difference from embodiment 1 is that:

[0075] The materials are prepared according to mass percentage: Si 1.3%, Mg 1.2%, Mn 1.0%, Sc 0.5%, Cr 0.1% and the balance is Al.

[0076] Example 4

[0077] In this embodiment 4, a Sc, Zr, Cr composite microalloyed Al-Si-Mg-Mn aluminum alloy is prepared according to the method of embodiment 1, and the difference from embodiment 1 is that:

[0078] The materials are prepared in percentage by mass: Si 1.3%, Mg 1.2%, Mn 1.0%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance is Al.

[0079] The raw material of Cr is Al-Cr master alloy, which is added simultaneously with Al-Sc and Al-Cr master alloy in the melting stage.

[0080] Example 5

[0081] In this embodiment 5, a Sc, Zr, Cr composite microalloyed Al-Si-Mg-Mn aluminum alloy is prepared according to the method of embodiment 4, and the difference from embodiment 4 is that:

[0082] The materials are prepared by mass percentage: Si 1.0%, Mg 0.9%, Mn 0.7%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance is Al;

[0083] The mold preheating temperature of this embodiment 5 is 200° C., the pressure during extrusion casting is 100 MPa, and the pressure holding condition is to hold the pressure at 100 MPa for 30 seconds.

[0084] Comparative Example 1

[0085] In this comparative example 1, an Al-Si-Mg-Mn aluminum alloy without adding Sc, Zr, and Cr is prepared according to the method of Example 1. The difference from Example 1 is that:

[0086] The materials are prepared by mass percentage: Si 0.7%, Mg 0.6%, Mn 0.4% and the balance Al.

[0087] The room temperature mechanical properties and high temperature mechanical properties of Examples 1 to 5 and Comparative Example 1 were tested respectively, and the results are shown in Table 1. It can be seen that the Al-Si-Mg-Mn aluminum alloys micro-alloyed with Sc and Zr or Sc, Zr and Cr have significantly improved tensile strength, yield strength and elongation at room temperature and at a high temperature of 250°C compared with the aluminum alloys without micro-alloying, especially the micro-alloying of Sc, Zr and Cr, which reduces the cost and improves the mechanical properties.

[0088] Figure 1 The metallographic microstructures of the aluminum alloys prepared in Comparative Example 1 and Examples 1 to 5 are shown respectively. It can be seen that Examples 1 to 5 have significantly smaller grain sizes than Comparative Example 1.

[0089] Table 1

[0090]

[0091] The above is a detailed introduction to the specific implementation methods of the present application. For those skilled in the art, several improvements and modifications may be made to the present application without departing from the principles of the present application. These improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A composite microalloyed aluminum alloy, characterized in that: According to mass percentage, it is composed of the following components: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Micro alloying elements 0.2%-0.6%, The balance is Al; Wherein, the micro-alloying elements are Sc and Cr, or the micro-alloying elements are Sc, Cr and Zr.

2. The composite microalloyed aluminum alloy according to claim 1, characterized in that: Calculated by mass percentage, it is composed of the following components: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc 0.1%-0.5%, Cr 0.1%, and the balance is Al.

3. The composite microalloyed aluminum alloy according to claim 1, characterized in that: Calculated by mass percentage, it is composed of the following components: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance is Al.

4. A solidification forming preparation process of a composite microalloyed aluminum alloy as claimed in claim 1, characterized in that: The steps include: S1, complete the batching according to the designed alloy composition; S2, placing the ingredients in a heating furnace until they are completely melted and mechanically stirred; S3, applying ultrasonic vibration to the completely melted molten alloy; S4, refining, slagging, temperature-controlled standing, and obtaining an aluminum alloy solution; S5, pouring the metal solution after standing into a preheated mold, extrusion casting and pressure holding, and cooling to obtain an aluminum alloy casting; S6, subjecting the aluminum alloy casting formed by extrusion casting to solid solution quenching treatment and aging treatment.

5. The solidification forming preparation process according to claim 4, characterized in that: The S2 comprises the following steps: S21, placing Al, Si, Mg, and Mn raw materials in a heating furnace and maintaining the temperature at 750-780° C. until they are completely melted; S22, maintaining the temperature at 750-780°C, and continuously adding Al-Sc, Al-Zr and Al-Cr master alloy raw materials until they are completely melted.

6. The solidification forming preparation process according to claim 4, characterized in that: The specific parameters of applying ultrasonic vibration in S3 are: ultrasonic power of 1000-2000W, amplitude of 0.1-100 μm, ultrasonic time of 100-1000s, and ultrasonic frequency of 10-20kHz.

7. The solidification forming preparation process according to claim 4, characterized in that: The specific process of S4 includes: adding a refining agent to the completely molten metal solution for refining, maintaining the temperature at 750-780°C during refining, skimming the slag after refining, and controlling the temperature to maintain at 750-780°C for 10 minutes.

8. The solidification forming preparation process according to claim 7, characterized in that: The refining agent is C2Cl6, and the amount of the refining agent added is 1wt% of the total mass of the metal solution.

9. The solidification forming preparation process according to claim 4, characterized in that: The specific process conditions in S5 are: the mold preheating temperature is 280-300° C., the pressure of extrusion casting is 150-200 MPa, and the pressure holding condition is to maintain the pressure at 100-200 MPa for 30-120 seconds.

10. The solidification forming preparation process according to claim 4, characterized in that: The solution quenching treatment in S6 is to keep the aluminum alloy casting at a temperature of 520-540°C for 10-12 hours and then cool it to room temperature; the aging treatment is to keep the aluminum alloy casting after the solution quenching treatment at a temperature of 170-190°C for 11-13 hours and then cool it to room temperature.

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