Composite microalloyed aluminum alloy and solidification forming preparation process thereof

Abstract

The application discloses a composite micro-alloyed aluminum alloy, which 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%, micro-alloying elements 0.2%-0.6%, and the balance of Al; wherein the micro-alloying elements are Sc and Cr, or the micro-alloying elements are Sc, Cr and Zr. By adding the micro-alloying elements, the aluminum alloy obtained in the application has excellent mechanical properties at room temperature and high temperature. The application also discloses a solidification forming preparation process of the aluminum alloy, and the ultrasonic auxiliary vibration is further used to promote the uniform dispersion of elements and improve the overall performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to a composite micro-alloyed aluminum alloy and a solidification forming preparation process thereof. BACKGROUND

[0002] In modern manufacturing industry, Al-Si-Mg-Mn alloy has been widely used in various complex component manufacturing fields due to its low density, high specific strength and excellent processing performance. With the continuous progress of manufacturing technology, extrusion casting process, which combines the advantages of traditional casting and forging process, has gradually become a key technology for aluminum alloy component production. This process not only realizes the near-net forming of complex-shaped components, but also effectively improves the organizational density and comprehensive mechanical properties of the components.

[0003] However, with the rapid development of the new energy automobile industry, higher requirements are put forward for the service performance of chassis and body structure parts. The existing Al-Si-Mg-Mn alloy has been difficult to meet the demand of high-performance application scenarios in terms of fatigue resistance, deformation resistance and high-temperature service performance. Specifically, the traditional casting process inevitably produces microscopic hole defects, which can easily cause stress concentration; at the same time, the existing Al-Si-Mg-Mn alloy is difficult to achieve the use target requirements of 300MPa yield strength and 8% elongation; in addition, the non-equilibrium segregation of elements such as Mg in the alloy at the grain boundary will accelerate the grain boundary sliding under high temperature conditions, thereby making the high-temperature mechanical properties of the alloy poor. Based on the above situation, it is urgent to develop an aluminum alloy material with better performance and its preparation process. SUMMARY

[0004] The purpose of the present application is to provide a composite micro-alloyed aluminum alloy and a solidification forming preparation process thereof, so as to solve the deficiencies 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 by the following technical solutions:

[0006] A composite micro-alloyed aluminum alloy, consisting of the following components in terms of mass percentage:

[0007] Si 0.7%-1.3%,

[0008] Mg 0.6%-1.2%,

[0009] Mn 0.4%-1.0%,

[0010] micro-alloying element 0.2%-0.6%,

[0011] the balance is Al;

[0012] 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 being 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 being Al.

[0015] A solidification forming preparation process of the composite micro-alloyed aluminum alloy as described above, comprising the following steps:

[0016] S1, completing the ingredient according to the designed alloy components;

[0017] S2, placing the ingredient in a heating furnace until completely melted and mechanically stirring;

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

[0019] S4, refining, skimming, temperature control and standing to obtain an aluminum alloy solution;

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

[0021] S6, solid solution quenching treatment and aging treatment of the aluminum alloy casting after extrusion casting forming.

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

[0023] S21, placing Al, Si, Mg and Mn raw materials in a heating furnace and maintaining a temperature of 750-780℃ until completely melted;

[0024] S22, maintaining a temperature of 750-780℃ and continuously adding Al-Sc, Al-Zr and Al-Cr intermediate alloy raw materials until completely melted.

[0025] Further, the ultrasonic vibration parameters in the S3 are as follows: ultrasonic power is 1000-2000W, amplitude is 0.1-100μm, ultrasonic time is 100-1000s, and ultrasonic frequency is 10-20kHz.

[0026] Further, the S4 specific process comprises: adding a refining agent to the completely melted metal solution for refining, the temperature is maintained at 750-780 DEG C during refining, slagging is performed after refining, and the temperature is controlled to maintain at 750-780 DEG C for 10 min.

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

[0028] Further, the specific process condition in S5 is that the mold preheating temperature is 280-300 DEG C, the pressure for extrusion casting is 150-200 Mpa, and the pressure maintaining condition is to maintain at 100-200 Mpa for 30-120 s.

[0029] Further, the solid solution quenching treatment in S6 is to maintain the aluminum alloy casting at a temperature of 520-540 DEG C for 10-12 h and then cool to room temperature, and the aging treatment is to maintain the aluminum alloy casting after the solid solution quenching treatment at a temperature of 170-190 DEG C for 11-13 h and then cool to room temperature.

[0030] The embodiment of the application provides a composite micro-alloyed aluminum alloy and a solidification forming preparation process thereof, and at least has the following beneficial effects:

[0031] The application adds trace amounts of Sc, Zr and Cr in the Al-Si-Mg-Mn alloy to obtain a new type of composite micro-alloyed aluminum alloy, forms Al3(Sc 1-x Zr x ) second phase particles and Al-(FeMnCr)Si phase, realizes fine grain strengthening and dispersion strengthening effect, and in combination with further improvement of the preparation process, can prepare the aluminum alloy component which is low in cost, dense in structure, excellent in comprehensive mechanical properties, maintains good mechanical properties and structural stability during high temperature service, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The metallographic microstructures of different embodiment and comparative example alloys are shown in (a) comparative example 1, (b) embodiment 1, (c) embodiment 2, (d) embodiment 3, (e) embodiment 4, and (f) embodiment 5. DETAILED DESCRIPTION

[0033] Hereinafter, the application is further described based on the preferred embodiments and with reference to the drawings. The various raw materials used in the application are all commercially available products, and the following embodiments will help the person skilled in the art to further understand the application, but do not limit the application in any form.

[0034] The application provides a composite micro-alloyed aluminum alloy, which is composed of the following components in percentage by mass:

[0035] Si 0.7%-1.3%,

[0036] Mg 0.6%-1.2%,

[0037] Mn 0.4%-1.0%,

[0038] Microalloying elements: 0.2%-0.6%,

[0039] The balance is Al;

[0040] Wherein, the microalloying elements are Sc and Cr, or the microalloying elements are Sc, Cr and Zr.

[0041] In some preferred embodiments, the composite microalloyed aluminum alloy of this 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%, with the balance being Al;

[0042] The addition of rare earth element Sc as a microalloying element improves the mechanical properties, weldability, creep resistance, and corrosion resistance of aluminum-based alloys. During solidification, it forms a large number of Al3Sc particles, and the lattice mismatch between the Al3Sc phase and the α-Al phase is 1.0% (<5%), meaning Al3Sc can act as a heterogeneous nucleant for α-Al, promoting grain refinement. While an appropriate amount of Al3Sc precipitates can refine grains and improve alloy strength, excessive Sc content can lead to excessive aggregation of Al3Sc particles at grain boundaries or within grains, affecting grain boundary movement and reducing the alloy's plasticity under high temperature or stress, thus increasing brittleness. Furthermore, a high Sc content may affect the alloy's heat treatment process, especially during aging treatment, where excessive Sc may alter the distribution and morphology of the precipitates, thereby affecting the alloy's strength and ductility.

[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 the Al-(FeMnCr)Si phase. This phase is distributed around the eutectic Si, which helps to transform the coarse eutectic Si particles into fine fibrous structures, thereby further improving the mechanical properties of the alloy. In addition, the Al-(FeMnCr)Si phase has higher stability than the Mg2Si phase at high temperatures, which enables the alloy to maintain good mechanical properties and structural stability during high-temperature service.

[0045] Although the addition of rare earth element Sc can effectively improve the mechanical properties of aluminum alloy, the cost of Sc is very high, therefore the present application further introduces Zr to partially replace Sc, which can reduce the cost and 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 by mass percentage: 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.

[0046] Sc and Zr effectively refine the grains through a heterogeneous nucleation mechanism, and interact with the matrix elements to generate stable compounds or solid solutions, significantly inhibiting grain boundary migration and recrystallization process; Zr and Sc form Al3(Sc 1-x Zr x ) phase with L12 structure during solidification, which can improve the strength of the alloy through the Orowan strengthening mechanism, and this phase has higher stability at high temperature; in addition, Al3(Sc, Zr) phase will also precipitate during solidification, and since the lattice mismatch between Al3Zr phase and alpha-Al phase is about 0.5%, the partial substitution of Sc by Zr can also reduce the lattice mismatch with alpha-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-mentioned elements, there is also an impurity element Fe, which tends to accumulate at the solid-liquid interface during solidification, forming an AlFeMnSi phase that is coarse, hard and brittle, and has high thermal shrinkage. This phase is an impurity phase that will cause significant fragmentation of the matrix, increase thermal brittleness, and make the casting more prone to cracking; in addition, this iron-rich impurity phase also reduces the strength and ductility of the alloy as a stress concentration point. The addition of the above-mentioned micro-alloying elements can significantly change the morphology of the iron-rich impurity phase, converting it from a needle-like or coarse skeletal structure to a small, broken, spherical and edge-passivated structure, which effectively alleviates the negative effects of the iron-rich impurity phase, avoids stress concentration during stretching, and thus improves the strength and ductility of the alloy.

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

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

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

[0051] S2, melting the ingredients in S1 in a heating furnace, the melting temperature is 750-780℃;

[0052] Further, the S2 specifically comprises the following steps:

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

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

[0055] In some embodiments, the heating furnace is a pit furnace.

[0056] In some 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 and applying ultrasonic vibration; specifically, the ultrasonic power is 1000-2000 W, the amplitude is 0.1-100 μm, the ultrasonic time is 100-1000 s, and the ultrasonic frequency is 10-20 kHz; by applying ultrasonic vibration, the agglomerated particles in the alloy can be effectively broken, promoting the uniform distribution of different components, thereby improving the microstructure and performance of the alloy.

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

[0059] After refining, slagging is performed, and the metal solution is subjected to temperature control and standing; specifically, the standing temperature is maintained at 750-780℃, and the standing time is 10 min.

[0060] S5, casting the metal solution after standing into a preheated mold, extrusion casting forming and pressure holding, and then taking out the casting; in some preferred embodiments, the mold preheating temperature is 280-300℃, and by appropriately adjusting the mold preheating temperature, the flowability of the metal liquid is improved, making it easier to fill the mold cavity, and reducing the occurrence of underfilling; in some preferred embodiments, the pressure of the extrusion casting forming is 150-200 MPa, by applying pressure, comprehensive liquid feeding and plastic deformation are provided to offset the tensile stress generated due to solidification shrinkage, avoid the generation of shrinkage voids and micro-cracks, and at the same time, reduce the air bubbles in the casting; in some preferred embodiments, the pressure holding condition is to maintain 30-120 s under a pressure of 100-200 MPa.

[0061] S6, the aluminum alloy castings after extrusion casting are subjected to solid solution quenching treatment and aging treatment; specifically, the solid solution quenching treatment is to heat the aluminum alloy castings at a temperature of 520-540℃ for 10-12h, and then water-cooled to room temperature; the aging treatment is to heat the aluminum alloy castings after the solid solution quenching treatment at a temperature of 170-190℃ for 11-13h, and then furnace-cooled to room temperature.

[0062] Example 1

[0063] In this embodiment, an Al-Si-Mg-Mn aluminum alloy with Sc and Cr composite micro-alloying is prepared, which is specifically implemented according to the following steps:

[0064] According to the mass percentage: Si 0.7%, Mg 0.6%, Mn 0.4%, Sc 0.1%, Cr 0.1%, and the balance of Al, the raw materials are prepared, the Al, Si, Mg and Mn in the raw materials are added to the well-type heating furnace, the temperature in the furnace is controlled at 750-780℃, and the above-mentioned metals are completely melted, then the Al-Sc and Al-Cr intermediate alloy in the raw materials are added, after completely melted, the mechanical stirring equipment is used to stir at a speed of 200-300rpm for 30 minutes;

[0065] An ultrasonic probe is inserted into the above-mentioned molten alloy, and ultrasonic vibration is applied, 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] C2Cl6 is added to the above-mentioned molten alloy for refining, the addition amount of the refining agent is 1wt% of the total mass of the metal solution, and after the refining is completed, the slag is removed; the metal solution after refining is placed for 10 minutes, and the standing temperature is kept at 750-780℃;

[0067] The alloy solution after standing is poured into a mold preheated to 300℃, a four-column hydraulic machine is used to apply a pressure of 150Mpa for extrusion casting, then the pressure is kept for 60s under the pressure of 150Mpa, and the castings are taken out after cooling;

[0068] The aluminum alloy castings after extrusion casting are heated to 520℃-540℃ for solid solution treatment, and after holding for 10-12 hours, the furnace is discharged, and quickly water quenched to room temperature;

[0069] The aluminum alloy castings after quenching are heated to 170℃-190℃, and held for 11-13 hours for aging treatment, and then naturally cooled to room temperature after discharging.

[0070] Example 2

[0071] Example 2

[0072] The raw materials were prepared according to the following mass percentages: Si 1.0%, Mg 0.9%, Mn 0.7%, Sc 0.3%, Cr 0.1%, and the balance being Al.

[0073] Example 3

[0074] Example 3 was prepared according to the method of Example 1 to obtain an Al-Si-Mg-Mn aluminum alloy with Sc and Cr composite micro-alloying, and the difference from Example 1 was that:

[0075] The raw materials were prepared according to the following mass percentages: Si 1.3%, Mg 1.2%, Mn 1.0%, Sc 0.5%, Cr 0.1%, and the balance being Al.

[0076] Example 4

[0077] Example 4 was prepared according to the method of Example 1 to obtain an Al-Si-Mg-Mn aluminum alloy with Sc, Zr, and Cr composite micro-alloying, and the difference from Example 1 was that:

[0078] The raw materials were prepared according to the following mass percentages: Si 1.3%, Mg 1.2%, Mn 1.0%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance being Al.

[0079] The raw material of Cr was an Al-Cr intermediate alloy, which was added at the same time as Al-Sc and Al-Cr intermediate alloy at the melting stage.

[0080] Example 5

[0081] Example 5 was prepared according to the method of Example 4 to obtain an Al-Si-Mg-Mn aluminum alloy with Sc, Zr, and Cr composite micro-alloying, and the difference from Example 4 was that:

[0082] The raw materials were prepared according to the following mass percentages: Si 1.0%, Mg 0.9%, Mn 0.7%, Sc 0.3%, Zr 0.2%, Cr 0.1%, and the balance being Al.

[0083] The mold preheating temperature of Example 5 was 200°C, and the pressure for extrusion casting was 100Mpa, and the pressure holding condition was 30s at a pressure of 100Mpa.

[0084] Comparative Example 1

[0085] Comparative Example 1 was prepared according to the method of Example 1, except that no Sc, Zr, Cr was added, and the difference from Example 1 was that:

[0086] The raw materials were prepared according to the following mass percentages: Si 0.7%, Mg 0.6%, Mn 0.4%, and the balance being Al.

[0087] The room temperature mechanical properties and high temperature mechanical properties of Example 1-Example 5 and Comparative Example 1 were tested, and the results are shown in Table 1. It can be seen that the Al-Si-Mg-Mn aluminum alloy with Sc and Zr, or Sc, Zr and Cr composite micro-alloying has significantly improved tensile strength, yield strength and elongation at room temperature and at 250°C high temperature compared with the aluminum alloy without composite micro-alloying. Especially, Sc, Zr and Cr composite micro-alloying reduces the cost while improving the mechanical properties.

[0088] Figure 1 The metallographic microstructure of the aluminum alloy prepared in Comparative Example 1 and Example 1-Example 5 is shown respectively, and it can be seen that Example 1-Example 5 has significantly smaller grain size than Comparative Example 1.

[0089] Table 1

[0090]

[0091] The specific embodiments of the application are described above in detail, and those skilled in the art can make some improvements and modifications to the application without departing from the principles of the application. These improvements and modifications also belong to the protection scope of the claims of the application.

Claims

1. A composite microalloyed aluminum alloy characterized by, consists of the following components by mass percentage: Si 0.7%-1.3%, Mg 0.6%-1.2%, Mn 0.4%-1.0%, micro-alloying elements 0.2%-0.6%, the balance being Al; wherein the micro-alloying elements are Sc, Cr and Zr, and the contents are respectively Sc 0.3%, Zr 0.2%, and Cr 0.1%; the composite micro-alloyed aluminum alloy is obtained by a solidification forming preparation process, the solidification forming preparation process comprising the following steps: S1, completing ingredient according to the designed alloy components; S2, placing the ingredient in a heating furnace until completely melted, and performing mechanical stirring; S3, applying ultrasonic vibration to the completely melted molten alloy; S4, refining, skimming, temperature control and standing to obtain an aluminum alloy solution; S5, casting the metal solution after standing into a preheated mold, extrusion casting forming and pressure maintaining, and cooling to obtain an aluminum alloy casting; S6, solid solution quenching treatment and aging treatment of the aluminum alloy casting after extrusion casting forming; the specific parameters of the ultrasonic vibration in S3 are: ultrasonic power is 1000-2000 W, amplitude is 0.1-100 μm, ultrasonic time is 100-1000 s, and ultrasonic frequency is 10-20 kHz; the solid solution quenching treatment in S6 is to heat the aluminum alloy casting at a temperature of 520-540℃ for 10-12 h and then cool to room temperature; the aging treatment is to heat the aluminum alloy casting after the solid solution quenching treatment at a temperature of 170-190℃ for 11-13 h and then cool to room temperature.

2. A process for the production of a solidification formed composite microalloyed aluminium alloy as claimed in claim 1, characterised in that, comprising the following steps: S1, completing ingredient according to the designed alloy components; S2, placing the ingredient in a heating furnace until completely melted, and performing mechanical stirring; S3, applying ultrasonic vibration to the completely melted molten alloy; S4, refining, skimming, temperature control and standing to obtain an aluminum alloy solution; S5, casting the metal solution after standing into a preheated mold, extrusion casting forming and pressure maintaining, and cooling to obtain an aluminum alloy casting; S6, solid solution quenching treatment and aging treatment of the aluminum alloy casting after extrusion casting forming.

3. The coagulatively forming production process according to claim 2, characterized in that the S2 comprises the following steps: S21, placing Al, Si, Mg and Mn raw materials in a heating furnace, and maintaining a temperature of 750-780℃ until completely melted; S22, maintaining the temperature of 750-780℃, and continuously adding Al-Sc, Al-Zr and Al-Cr intermediate alloy raw materials until completely melted.

4. The coagulatively forming production process according to claim 2, characterized in that the S4 comprises the following specific process: adding a refining agent to the completely melted metal solution for refining, maintaining the temperature at 750-780℃ during refining, skimming after refining, and controlling the temperature at 750-780℃ for standing for 10 min.

5. The coagulatively forming production process according to claim 4, characterized in that the refining agent is C2Cl6, and the addition amount of the refining agent is 1wt% of the total mass of the metal solution.

6. The coagulatively forming production process according to claim 2, characterized in that the specific process conditions in S5 are: the mold preheating temperature is 280-300℃, the pressure of the extrusion casting forming is 150-200 MPa, and the pressure maintaining condition is to maintain at a pressure of 100-200 MPa for 30-120 s.

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