Rare earth aluminum alloy for high-pressure casting of thin-wall motor shell and preparation method of rare earth aluminum alloy

Abstract

The invention discloses a rare earth aluminum alloy for high-pressure casting of a thin-wall type motor shell and a preparation method of the rare earth aluminum alloy, and relates to the technical field of aluminum alloys, the rare earth aluminum alloy for high-pressure casting of the thin-wall type motor shell comprises the following components in percentage by mass: 6.0-9.0% of Si, 0.2-0.5% of Mg, 0.05-0.25% of Sn, 0.20-0.45% of Ti, 0.15-0.35% of Zn, 0.01-0.03% of Sr, 0.4-0.7% of Fe, 0.1-0.5% of Cu and 0.01-0.1% of Ni. Through matching of multi-element alloy elements such as Si, Mg and Sn, the multi-element alloy elements and rare earth elements such as Ce, Y and La form a synergistic effect, meanwhile, grains are refined, the form and distribution of a second phase are optimized, the structure is further refined by means of elements such as Ti and Zr, and therefore synchronous optimization and balanced improvement of the tensile strength, the yield strength and the percentage elongation after fracture of the alloy are achieved.

Description

Technical Field

[0001] This application relates to the field of aluminum alloy technology, and in particular to rare earth aluminum alloys for use in high-pressure die-casting thin-walled motor housings and their preparation methods. Background Technology

[0002] In the current era of rapid development in the new energy vehicle industry, lightweighting has become a core technological direction for improving vehicle range, power performance, and handling safety. Aluminum alloys, with a density only about one-third that of steel and possessing excellent mechanical properties and casting characteristics, are widely used in the manufacture of key components such as motor housings. Their usage has become one of the important indicators for measuring the competitiveness of new energy vehicle products. High-pressure casting, as a highly efficient forming process, can achieve integrated manufacturing of complex structural components, possessing irreplaceable advantages in the production of thin-walled motor housings. The development of high-performance aluminum alloy materials adapted to high-pressure casting is key to promoting the thinning and lightweighting of motor housings.

[0003] Currently, the aluminum alloys used for high-pressure casting of motor housings on the market are mainly traditional cast aluminum alloys such as A356.0. These alloys, through reasonable component ratios and heat treatment processes, can meet the basic usage requirements of conventional motor housings. Their typical composition uses Al as the matrix, combined with Si, Mg, and other major alloying elements. Si enhances the alloy's fluidity to adapt to the casting process, while Mg forms the Mg2Si strengthening phase with Si to improve mechanical properties. Some grades add small amounts of Ti, Fe, and other elements to optimize the microstructure and processing performance. In the preparation process, traditional aluminum alloys typically use a single melting furnace to add all raw materials at once. After heating, melting, and mixing, they are directly subjected to high-pressure casting. This process is relatively simple and mature, and has been used for a long time in the automotive parts manufacturing industry.

[0004] However, traditional cast aluminum alloys have a relatively simple composition, relying only on a few core elements such as Si and Mg to regulate performance. This results in large grain size and uneven distribution of the second phase in the alloy microstructure, leading to limited mechanical properties. Furthermore, it is difficult to balance tensile strength, yield strength, and elongation after fracture, which prevents the motor housing from being further thinned, thus hindering the improvement of the overall vehicle lightweighting effect. Summary of the Invention

[0005] The purpose of this invention is to provide a rare earth aluminum alloy for high-pressure casting of thin-walled motor housings and its preparation method, which at least solves the problem that traditional cast aluminum alloys have limited mechanical properties and it is difficult to balance tensile strength, yield strength and elongation after fracture, which prevents the motor housing from being further thinned and restricts the improvement of the overall vehicle lightweighting effect.

[0006] This invention provides the following solution:

[0007] In a first aspect, this application provides a rare earth aluminum alloy for use in high-pressure die-casting thin-walled motor housings, comprising the following components by mass percentage: Si 6.0~9.0%, Mg 0.2~0.5%, Sn 0.05~0.25%, Ti 0.20~0.45%, Zn 0.15~0.35%, Sr 0.01~0.03%, Fe 0.4~0.7%, Cu 0.1~0.5%, Ni 0.01~0.1%, Zr 0.05~0.2%, Mo 0.05~0.15%, V 0.05~0.25%, Cr 0.1~0.4%, Ce 0.1~0.3%, Y 0.1~0.3%, La 0.1~0.3%, with the remainder being Al and other unavoidable impurity elements.

[0008] By adopting the above technical solution, a synergistic effect is achieved by combining multiple alloying elements such as Si, Mg, and Sn with rare earth elements such as Ce, Y, and La. On the one hand, the purification effect of rare earth elements is used to remove harmful impurities in the alloy melt, while refining the grains and optimizing the morphology and distribution of the second phase. On the other hand, through the complementary functions of each alloying element, Si is used to improve the casting fluidity of the alloy, while Mg, Cu and other elements form a strengthening phase, and Ti, Zr and other elements further refine the microstructure. This achieves simultaneous optimization and balanced improvement of the alloy's tensile strength, yield strength and elongation after fracture. This solves the problem that traditional cast aluminum alloys have limited mechanical properties and it is difficult to balance tensile strength, yield strength and elongation after fracture, which prevents the motor housing from being further thinned and restricts the improvement of the overall vehicle's lightweight effect.

[0009] Preferably, the raw material for Si is an Al-Si alloy, the raw material for Mg is pure Mg, the raw material for Sn is an Al-Sn alloy, the raw material for Ti is an Al-Ti alloy, the raw material for Zn is an Al-Zn alloy, the raw material for Sr is an Al-Sr alloy, the raw material for Fe is an Al-Fe alloy, the raw material for Cu is an Al-Cu alloy, the raw material for Ni is an Al-Ni alloy, the raw material for Zr is an Al-Zr alloy, the raw material for Mo is an Al-Mo alloy, the raw material for V is an Al-V alloy, the raw material for Cr is an Al-Cr alloy, the raw material for Ce is an Al-Ce alloy, the raw material for Y is an Al-Y alloy, the raw material for La is an Al-La alloy, and the raw material for Al is pure Al.

[0010] By adopting the above technical solutions, the combination of various types of raw materials can ensure that each alloying element is incorporated into the melt in the designed proportion, reduce element loss and composition fluctuation during the smelting process, promote uniform diffusion of each element, avoid local segregation, provide a guarantee for the stability and consistency of alloy performance, and give full play to the synergistic effect of multi-element alloying elements and rare earth elements.

[0011] Secondly, this application provides a method for preparing rare earth aluminum alloys for high-pressure die-casting thin-walled motor housings, comprising the following steps:

[0012] First processing: Calculate and weigh according to mass percentage, add pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy and Al-Cr alloy into a melting furnace, heat, stir and mix, and hold at the temperature to obtain the first alloy melt;

[0013] Secondary processing: Calculate and weigh according to mass percentage, add pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy and Al-La alloy to the first alloy melt, heat, stir and mix, and keep at the temperature to obtain the second alloy melt;

[0014] Three processes: Calculate and weigh the Al-Sr alloy and Al-Ti alloy by mass percentage, add them to the second alloy melt, heat, stir and mix, and hold at the temperature to obtain the third alloy melt;

[0015] Temperature-controlled casting: After controlling the temperature of the third alloy melt, high-pressure casting is performed to obtain a thin-walled motor housing.

[0016] By adopting the above technical solution and performing alloying treatment in batches according to the physicochemical properties of the elements, the problems of easily oxidized elements burning off and high-melting-point elements not dissolving sufficiently can be avoided, ensuring that each element reacts fully and is evenly distributed. At the same time, the melt composition and state are gradually optimized, laying the process foundation for the balanced improvement of the alloy's mechanical properties and casting fluidity, and adapting to the high-pressure casting molding requirements of thin-walled motor housings.

[0017] Preferably, in the first processing step, the preheating furnace is preheated to 190-210°C at a heating rate of 9-11°C / min before being added, and the heating temperature is 750-780°C.

[0018] By adopting the above technical solution, and by coordinating the preheating and heating rate of the melting furnace with the heating temperature, a suitable environment can be created for the full dissolution of high melting point elements, avoiding uneven melt composition caused by temperature fluctuations, while reducing reaction losses between the base metal and alloying elements, and ensuring the stability of the first alloy melt.

[0019] Preferably, in the first processing step, the stirring and mixing is carried out by electromagnetic stirring at a speed of 280-320 r / min for 16-17 min, the heat preservation time is 28-32 min, and the stirring is carried out once every 10 min during the heat preservation period, with each stirring time being 25-35 s.

[0020] By adopting the above technical solution, combining electromagnetic stirring with auxiliary stirring during heat preservation, it is possible to promote the rapid diffusion of various alloying elements, break the concentration gradient in the melt, avoid local component segregation, and extend the element reaction time to ensure the formation of a uniform and stable first alloy melt.

[0021] Preferably, in the secondary processing step, the addition rate is ≤50g / min, and the heating temperature is 740-760℃.

[0022] By adopting the above technical solution, and by controlling the raw material addition rate and matching an appropriate heating temperature, it is possible to avoid the burning and splashing of easily oxidized and low-melting-point elements due to violent melt reactions during the addition process, ensuring that such elements are incorporated into the first alloy melt in the designed proportion, and guaranteeing the accuracy of the composition of the second alloy melt.

[0023] Preferably, in the secondary processing step, the stirring and mixing is carried out by electromagnetic stirring at a speed of 230-270 r / min for 8-12 min, the heat preservation time is 18-22 min, and argon gas is introduced for protection during the heat preservation period, with a flow rate of 0.5-1 L / min.

[0024] By adopting the above technical solution, and by using mild electromagnetic stirring parameters in combination with argon protection and holding time, it is possible to promote the uniform mixing of rare earth elements with other alloying elements, effectively isolate air, reduce the loss of easily oxidized elements, and provide sufficient time for synergistic reactions between elements, thereby optimizing the microstructure of the second alloy melt.

[0025] Preferably, in the three processing steps, the addition is made by crushing the Al-Sr alloy and Al-Ti alloy into particles of 5-10 mm before adding them; the heating temperature is 720-740℃; the stirring and mixing is carried out by electromagnetic stirring at a speed of 180-220 r / min for 4-6 min; and the holding time is 12-17 min.

[0026] By adopting the above technical solution, the raw materials are crushed into specific particle sizes and added at a suitable temperature. With gentle stirring and heat preservation parameters, the modifier and grain refiner can be rapidly and uniformly dispersed, avoiding their aggregation or volatilization failure, giving full play to their role in optimizing the melt structure, and ensuring the forming performance of the third alloy melt.

[0027] Preferably, before the temperature-controlled casting step, 0.1-0.2% of hexachloroethane refining agent by mass of the third alloy melt is added to the third alloy melt, and electromagnetic stirring is performed at a stirring rate of 200-250 r / min for 3-5 min, followed by standing for 8-12 min.

[0028] By adopting the above technical solution, and combining the refining agent with stirring and settling parameters, hydrogen and non-metallic inclusions in the melt can be effectively adsorbed, reducing defects such as porosity and inclusions inside the casting. At the same time, the purity and uniformity of the melt are further improved, providing a high-quality melt for subsequent high-pressure casting.

[0029] Preferably, in the temperature-controlled casting step, the temperature is 680-720℃, the high-pressure casting uses a die-casting machine with a pressure of 60-80MPa and an injection speed of 6.0-8.0m / s, and the mold is preheated to 200-250℃ before high-pressure casting.

[0030] By adopting the above technical solution, matching the melt temperature with the mold preheating temperature, and coordinating the die casting pressure and injection speed, the fluidity advantage of the alloy melt can be fully utilized to ensure the complete filling of the thin-walled cavity, while reducing defects such as cracks and shrinkage cavities caused by rapid cooling of the melt, thereby improving the forming quality and dimensional accuracy of the motor housing casting.

[0031] The above solution achieves the following beneficial technical effects:

[0032] This application combines multiple alloying elements such as Si, Mg, and Sn with rare earth elements such as Ce, Y, and La to form a synergistic effect. On the one hand, the purification effect of rare earth elements is used to remove harmful impurities in the alloy melt, while refining the grains and optimizing the morphology and distribution of the second phase. On the other hand, through the complementary functions of each alloying element, Si is used to improve the casting fluidity of the alloy, while Mg, Cu and other elements form a strengthening phase, and Ti, Zr and other elements further refine the microstructure. This achieves simultaneous optimization and balanced improvement of the alloy's tensile strength, yield strength and elongation after fracture. This solves the problem that traditional cast aluminum alloys have limited mechanical properties and it is difficult to balance tensile strength, yield strength and elongation after fracture, which prevents the motor housing from being further thinned and restricts the improvement of the overall vehicle's lightweight effect.

[0033] This application reduces harmful impurities in the melt by controlling the Si content and utilizing the purification effect of rare earth elements. At the same time, it ensures uniform dispersion of each element through a step-by-step melting process, thereby improving the fluidity of the alloy melt. In the high-pressure casting process, the excellent fluidity can ensure that the melt fills the thin-walled cavity quickly and completely, effectively reducing molding defects such as incomplete filling, porosity, and inclusions, and improving the molding qualification rate of thin-walled motor housings. It also provides process feasibility for the integrated casting of complex structure motor housings.

[0034] This application utilizes the proportions of multiple alloying elements, the synergistic effect of rare earth elements and other alloying elements, and stepwise melting based on the physicochemical properties of the elements. This results in a balanced and excellent mechanical property in terms of tensile strength, yield strength, and elongation after fracture, enabling a reduction in the wall thickness of the motor housing compared to traditional products. This achieves weight reduction, decreases energy consumption during vehicle operation, and helps alleviate range anxiety in new energy vehicles. Simultaneously, the lighter vehicle body improves acceleration performance and handling agility, optimizing the driving experience. Furthermore, lightweight design promotes the green upgrading of the automotive industry chain, reducing carbon emissions during production and use, aligning with the energy-saving and environmentally friendly industrial development trend. Attached Figure Description

[0035] Figure 1 This is a flowchart of a method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings, provided by one or more embodiments of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Technical Concept: With the rapid development of the new energy vehicle industry, lightweighting has become a key direction for improving vehicle range and performance. As a critical component, the motor housing places higher demands on the mechanical properties and casting fluidity of aluminum alloy materials. Traditional high-pressure casting of aluminum alloys relies heavily on a few core elements such as Si and Mg to control performance, resulting in a single composition design. This leads to coarse alloy grains and uneven distribution of the second phase, making it difficult to simultaneously achieve high tensile strength, yield strength, and elongation after fracture, thus limiting mechanical properties. Furthermore, it restricts further thinning of the motor housing wall, failing to meet the demands of overall vehicle lightweighting upgrades. Simultaneously, the traditional single-melting process, which adds all raw materials at once, easily causes the loss of easily oxidized elements and insufficient dissolution of high-melting-point elements, further exacerbating compositional segregation and affecting alloy performance stability.

[0038] To address this technical challenge, this application employs a proportional combination of multi-element alloying elements such as Si, Mg, and Ti, along with rare earth elements Ce, Y, and La. The purification and refining effects of rare earth elements, combined with the complementary functions of other elements, optimize the alloy's microstructure and forming properties. Furthermore, the step-by-step melting process, which involves alloying elements in batches according to their physicochemical properties, avoids the shortcomings of traditional single-element melting, ensuring sufficient reaction and uniform distribution of each element. This achieves a simultaneous and balanced improvement in the alloy's mechanical properties and fluidity, supporting the thinning and lightweighting of motor housings.

[0039] Unless otherwise specified, all experimental methods used below are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in this field, which can be obtained commercially or prepared according to literature methods by those skilled in the art.

[0040] To better understand the above technical solutions, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0041] The following is a further description with reference to the embodiments:

[0042] Example 1:

[0043] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by mass percentage: Si 7.5%, Mg 0.35%, Sn 0.15%, Ti 0.325%, Zn 0.25%, Sr 0.02%, Fe 0.55%, Cu 0.3%, Ni 0.055%, Zr 0.125%, Mo 0.1%, V 0.15%, Cr 0.25%, Ce 0.2%, Y 0.2%, La 0.2%, with the remainder being Al and other unavoidable impurity elements.

[0044] The raw material for Si is Al-Si alloy, the raw material for Mg is pure Mg, the raw material for Sn is Al-Sn alloy, the raw material for Ti is Al-Ti alloy, the raw material for Zn is Al-Zn alloy, the raw material for Sr is Al-Sr alloy, the raw material for Fe is Al-Fe alloy, the raw material for Cu is Al-Cu alloy, the raw material for Ni is Al-Ni alloy, the raw material for Zr is Al-Zr alloy, the raw material for Mo is Al-Mo alloy, the raw material for V is Al-V alloy, the raw material for Cr is Al-Cr alloy, the raw material for Ce is Al-Ce alloy, the raw material for Y is Al-Y alloy, the raw material for La is Al-La alloy, and the raw material for Al is pure Al.

[0045] Please see the appendix Figure 1A method for preparing rare earth aluminum alloys for high-pressure casting thin-walled motor housings, applicable to the aforementioned rare earth aluminum alloys for high-pressure casting thin-walled motor housings, includes the following steps:

[0046] First processing: Calculate and weigh according to mass percentage, add pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy and Al-Cr alloy into a melting furnace, heat, stir and mix, and hold at the temperature to obtain the first alloy melt;

[0047] Secondary processing: Calculate and weigh according to mass percentage, add pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy and Al-La alloy to the first alloy melt, heat, stir and mix, and keep at the temperature to obtain the second alloy melt;

[0048] Three processes: Calculate and weigh the Al-Sr alloy and Al-Ti alloy by mass percentage, add them to the second alloy melt, heat, stir and mix, and hold at the temperature to obtain the third alloy melt;

[0049] Temperature-controlled casting: After controlling the temperature of the third alloy melt, high-pressure casting is performed to obtain a thin-walled motor housing.

[0050] In one processing step, the material is preheated in a pre-melting furnace at 200°C with a heating rate of 10°C / min, and then heated to 765°C.

[0051] In one processing step, the stirring and mixing are carried out by electromagnetic stirring at a speed of 300 r / min for 16.5 min, and the holding time is 30 min. During the holding time, the stirring is carried out once every 10 min, and each stirring time is 30 s.

[0052] In the secondary processing step, the addition rate is ≤50g / min, and the heating temperature is 750℃.

[0053] In the secondary processing step, electromagnetic stirring is used for mixing at a speed of 250 r / min for 10 min, and the holding time is 20 min. During the holding time, argon gas is introduced for protection at a flow rate of 0.75 L / min.

[0054] In the three processing steps, Al-Sr alloy and Al-Ti alloy were added after being crushed into 7.5mm particles. The heating temperature was 730℃, and the stirring and mixing were carried out by electromagnetic stirring at a speed of 200r / min for 5min, followed by a holding time of 14.5min.

[0055] Before the temperature-controlled casting step, add 0.15% of the mass of the third alloy melt with hexachloroethane refining agent to the third alloy melt, and then perform electromagnetic stirring at a stirring rate of 225 r / min for 4 min, followed by standing for 10 min.

[0056] In the temperature-controlled casting process, the temperature is controlled at 700℃. High-pressure casting uses a die-casting machine with a pressure of 70MPa and an injection speed of 7.0m / s. Before high-pressure casting, the mold is preheated to 225℃.

[0057] Example 2:

[0058] The difference between this embodiment and Embodiment 1 above is that:

[0059] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 6.0%, Mg 0.2%, Sn 0.05%, Ti 0.20%, Zn 0.15%, Sr 0.01%, Fe 0.4%, Cu 0.1%, Ni 0.01%, Zr 0.05%, Mo 0.05%, V 0.05%, Cr 0.1%, Ce 0.1%, Y 0.1%, La 0.1%, with the remainder being Al and other unavoidable impurity elements.

[0060] Example 3:

[0061] The difference between this embodiment and Embodiment 1 above is that:

[0062] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 9.0%, Mg 0.5%, Sn 0.25%, Ti 0.45%, Zn 0.35%, Sr 0.03%, Fe 0.7%, Cu 0.5%, Ni 0.1%, Zr 0.2%, Mo 0.15%, V 0.25%, Cr 0.4%, Ce 0.3%, Y 0.3%, La 0.3%, with the remainder being Al and other unavoidable impurity elements.

[0063] Example 4:

[0064] The difference between this embodiment and Embodiment 1 above is that:

[0065] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 6.7 wt%, Mg 0.4 wt%, Sn 0.09 wt%, Ti 0.25 wt%, Zn 0.2 wt%, Sr 0.01 wt%, Fe 0.4 wt%, Cu 0.3 wt%, Ni 0.04 wt%, Zr 0.15 wt%, Mo 0.05 wt%, V 0.2 wt%, Cr 0.15 wt%, Ce 0.1 wt%, Y 0.1 wt%, La 0.2 wt%, with the remainder being Al and other unavoidable impurity elements.

[0066] Based on the chemical composition and mass percentage of the aforementioned alloys, the raw materials were weighed and pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy, and Al-Cr alloy were added to a melting furnace and heated to 760°C. The mixture was stirred and mixed for the first alloying treatment, yielding alloy melt 1. Pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy, and Al-La alloy were added to alloy melt 1, and the mixture was heated to 750°C and stirred for the second alloying treatment, yielding alloy melt 2. Al-Sr alloy and Al-Ti alloy were added to alloy melt 2, and the mixture was heated to 740°C and stirred for the third alloying treatment, yielding alloy melt 3. The resulting alloy melt 3 was then subjected to high-pressure casting at 720°C, with the die-casting machine pressure set to 60 MPa and the injection speed set to 6.0 m / s to obtain thin-walled motor housing parts.

[0067] Example 5:

[0068] The difference between this embodiment and Embodiment 1 above is that:

[0069] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 8.5 wt%, Mg 0.3 wt%, Sn 0.2 wt%, Ti 0.4 wt%, Zn 0.3 wt%, Sr 0.02 wt%, Fe 0.6 wt%, Cu 0.1 wt%, Ni 0.08 wt%, Zr 0.1 wt%, Mo 0.15 wt%, V 0.15 wt%, Cr 0.2 wt%, Ce 0.2 wt%, Y 0.3 wt%, La 0.1 wt%, with the remainder being Al and other unavoidable impurity elements.

[0070] Based on the chemical composition and mass percentage of the aforementioned alloys, the raw materials were weighed and pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy, and Al-Cr alloy were added to a melting furnace and heated to 780℃. The mixture was stirred and mixed for the first alloying treatment, yielding alloy melt 1. Pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy, and Al-La alloy were added to alloy melt 1, and the mixture was heated to 740℃ and stirred for the second alloying treatment, yielding alloy melt 2. Al-Sr alloy and Al-Ti alloy were added to alloy melt 2, and the mixture was heated to 730℃ and stirred for the third alloying treatment, yielding alloy melt 3. The obtained alloy melt 3 was then subjected to high-pressure casting at 710℃, with the die-casting machine pressure set to 70MPa and the injection speed set to 7.0m / s to obtain thin-walled motor housing parts.

[0071] Example 6:

[0072] The difference between this embodiment and Embodiment 1 above is that:

[0073] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 7.5 wt%, Mg 0.15 wt%, Sn 0.12 wt%, Ti 0.3 wt%, Zn 0.25 wt%, Sr 0.03 wt%, Fe 0.5 wt%, Cu 0.4 wt%, Ni 0.05 wt%, Zr 0.15 wt%, Mo 0.12 wt%, V 0.2 wt%, Cr 0.3 wt%, Ce 0.3 wt%, Y 0.2 wt%, La 0.3 wt%, with the remainder being Al and other unavoidable impurity elements.

[0074] Based on the chemical composition and mass percentage of the aforementioned alloys, the raw materials were weighed and pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy, and Al-Cr alloy were added to a melting furnace and heated to 770°C. The mixture was stirred and mixed for the first alloying treatment, yielding alloy melt 1. Pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy, and Al-La alloy were added to alloy melt 1, and the mixture was heated to 750°C and stirred for the second alloying treatment, yielding alloy melt 2. Al-Sr alloy and Al-Ti alloy were added to alloy melt 2, and the mixture was heated to 740°C and stirred for the third alloying treatment, yielding alloy melt 3. The obtained alloy melt 3 was then subjected to high-pressure casting at 700°C, with the die-casting machine pressure set to 65 MPa and the injection speed set to 6.5 m / s to obtain thin-walled motor housing parts.

[0075] Comparative Example 1:

[0076] The difference between this comparative example and Example 1 above is that:

[0077] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by weight percentage: Si 7.5%, Mg 0.35%, Sn 0.15%, Ti 0.325%, Zn 0.25%, Sr 0.02%, Fe 0.55%, Cu 0.3%, Ni 0.055%, Zr 0.125%, Mo 0.1%, V 0.15%, Cr 0.25%, with the remainder being Al and unavoidable impurity elements.

[0078] Preparation method: No Al-Ce alloy, Al-Y alloy, or Al-La alloy is added in the secondary processing step; otherwise, it is the same as in Example 1.

[0079] Comparative Example 2:

[0080] The difference between this comparative example and Example 1 above is that:

[0081] Rare earth aluminum alloys used for high-pressure die-casting thin-walled motor housings comprise the following components by mass percentage: Si 7.5%, Mg 0.35%, Sn 0.15%, Ti 0.325%, Zn 0.25%, Sr 0.02%, Fe 0.55%, Cu 0.3%, Ni 0.055%, Zr 0.125%, Mo 0.1%, V 0.15%, Cr 0.25%, Ce 0.4%, Y 0.4%, La 0.4%, with the remainder being Al and unavoidable impurity elements.

[0082] Comparative Example 3:

[0083] The difference between this comparative example and Example 1 above is that:

[0084] The preparation method of rare earth aluminum alloy for high-pressure casting of thin-walled motor housings includes the following steps: weigh all raw materials according to the component mass percentage, add them all at once to a melting furnace preheated to 200°C, heat to 765°C at 10°C / min, electromagnetically stir at 300r / min for 30min, hold at that temperature for 20min, and manually stir for 30s every 10min during the holding period; the subsequent melt purification and temperature-controlled casting process parameters are exactly the same as in Example 1; there are no first, second, or third treatments.

[0085] The mechanical properties and alloy fluidity of the above embodiments and comparative examples were tested, and compared with those of traditional A356.0 die-cast aluminum alloy after T6 heat treatment. The test results are shown in Table 1:

[0086] Mechanical properties: According to GB / T 228.1-2010 standard, circular standard tensile specimens with a diameter of 10 mm and a gauge length of 50 mm were cut from the uniform wall thickness section of the casting, and 5 parallel specimens were prepared for each group. At 23±5℃, a WDW-100 universal tensile testing machine was used to stretch the specimens at a speed of 2 mm / min until fracture. The tensile strength, 0.2% yield strength, and elongation after fracture were calculated using force-displacement curves. Outliers were removed, and the average value was taken as the final result.

[0087] Alloy flowability: The spiral die casting method was used with H13 steel molds. The spiral diameter was 8 mm and the effective length was 200 mm. The mold was preheated to 225±5℃ and held for 30 min. The alloy melt was injected according to the corresponding group's die casting parameters. After cooling, the casting was removed, and the spiral forming length was measured using a vernier caliper with an accuracy of 0.01 mm. Each group was tested 5 times. After removing abnormal data caused by sticking or oxidation, the average value was taken as the flow distance result.

[0088] Table 1

[0089] Group Tensile strength Rm (MPa) Yield strength Rp0.2 (MPa) Elongation after fracture A (%) Flow distance (mm) Example 1 328 262 9.2 183 Example 2 310 245 9.0 172 Example 3 335 268 9.3 188 Example 4 315 255 9.0 175 Example 5 321 247 9.0 181 Example 6 306 238 9.0 173 Comparative Example 1 298 235 8.0 145 Comparative Example 2 290 228 7.8 138 Comparative Example 3 285 222 7.6 132 A356.0 293 229 7.5 124

[0090] As can be seen from Examples 1 to 6 and Comparative Example 1, along with Table 1, there is a significant synergistic effect between rare earth elements and other alloying elements. Rare earth elements can effectively refine the alloy microstructure, promote the uniform distribution of the second phase, and thus improve the mechanical properties and casting fluidity of the alloy. In the absence of rare earth elements, the microstructure refinement effect of the alloy is insufficient, and the performance improvement is significantly limited, thus confirming the crucial role of rare earth elements in optimizing the overall performance of the alloy.

[0091] Based on Examples 1 to 6 and Comparative Example 2, and in conjunction with Table 1, it can be seen that the amount of rare earth elements added needs to be controlled within a reasonable range so that the rare earth elements can fully exert their purification and refining effects and form a beneficial synergistic effect with other elements. However, excessive rare earth elements will form brittle intermetallic compounds with other elements, resulting in a decrease in the mechanical properties and fluidity of the alloy. This indicates that an appropriate amount of rare earth elements can ensure the performance of the alloy.

[0092] As can be seen from Examples 1 to 6 and Comparative Example 3, and in conjunction with Table 1, the stepwise melting process can improve alloy performance. Adding raw materials in batches according to the physicochemical properties of the elements avoids the burn-off of easily oxidized elements and the incomplete dissolution of high-melting-point elements, ensuring that all alloying elements are uniformly incorporated into the matrix. In contrast, the traditional single-melting process easily causes component segregation, thus affecting the overall performance of the alloy.

[0093] As can be seen from Examples 1 to 3 and Table 1, the combination of various alloy components enables rare earth aluminum alloys to maintain excellent mechanical properties and casting fluidity, achieving a balanced improvement in performance. This satisfies the filling requirements of high-pressure casting while ensuring the structural strength and toughness required for the motor housing.

[0094] As can be seen from Examples 1 to 6 and Table 1, the synergistic combination of multiple elements in the alloy can improve the overall performance of rare earth aluminum alloys. Specifically, Si provides good fluidity, Mg forms strengthening phases with other elements, Ti and Zr refine the grains, and rare earth elements further optimize the microstructure. These elements work together synergistically to achieve a balance between mechanical properties and casting performance. Furthermore, by matching the die-casting process parameters with the characteristics of the alloy melt, the fluidity of the alloy melt can be fully adapted, ensuring complete filling of the thin-walled cavity, reducing internal defects in the casting, and further maximizing the potential of the alloy's mechanical properties.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rare earth aluminum alloy for use in high-pressure die-casting thin-walled motor housings, characterized in that, It includes the following components by mass percentage: Si 6.0~9.0%, Mg 0.2~0.5%, Sn 0.05~0.25%, Ti 0.20~0.45%, Zn 0.15~0.35%, Sr 0.01~0.03%, Fe 0.4~0.7%, Cu 0.1~0.5%, Ni 0.01~0.1%, Zr 0.05~0.2%, Mo 0.05~0.15%, V 0.05~0.25%, Cr 0.1~0.4%, Ce 0.1~0.3%, Y 0.1~0.3%, La 0.1~0.3%, with the remainder being Al and other unavoidable impurity elements.

2. The rare earth aluminum alloy for high-pressure die-casting thin-walled motor housings according to claim 1, characterized in that, The raw material for Si is an Al-Si alloy, the raw material for Mg is pure Mg, the raw material for Sn is an Al-Sn alloy, the raw material for Ti is an Al-Ti alloy, the raw material for Zn is an Al-Zn alloy, the raw material for Sr is an Al-Sr alloy, the raw material for Fe is an Al-Fe alloy, the raw material for Cu is an Al-Cu alloy, the raw material for Ni is an Al-Ni alloy, the raw material for Zr is an Al-Zr alloy, the raw material for Mo is an Al-Mo alloy, the raw material for V is an Al-V alloy, the raw material for Cr is an Al-Cr alloy, the raw material for Ce is an Al-Ce alloy, the raw material for Y is an Al-Y alloy, the raw material for La is an Al-La alloy, and the raw material for Al is pure Al.

3. A method for preparing rare earth aluminum alloys for high-pressure casting thin-walled motor housings, characterized in that, The application of the rare earth aluminum alloy for high-pressure casting thin-walled motor housings as described in claim 1 or 2 includes the following steps: First processing: Calculate and weigh according to mass percentage, add pure Al, Al-Si alloy, Al-Fe alloy, Al-Ni alloy, Al-Zr alloy, Al-Mo alloy, Al-V alloy, Al-Zn alloy and Al-Cr alloy into a melting furnace, heat, stir and mix, and hold at the temperature to obtain the first alloy melt; Secondary processing: Calculate and weigh according to mass percentage, add pure Mg, Al-Sn alloy, Al-Cu alloy, Al-Ce alloy, Al-Y alloy and Al-La alloy to the first alloy melt, heat, stir and mix, and keep at the temperature to obtain the second alloy melt; Three processes: Calculate and weigh the Al-Sr alloy and Al-Ti alloy by mass percentage, add them to the second alloy melt, heat, stir and mix, and hold at the temperature to obtain the third alloy melt; Temperature-controlled casting: After controlling the temperature of the third alloy melt, high-pressure casting is performed to obtain a thin-walled motor housing.

4. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the first processing step, the preheating furnace is preheated to 190-210℃ at a heating rate of 9-11℃ / min, and the heating temperature is 750-780℃.

5. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the first processing step, the stirring and mixing is carried out by electromagnetic stirring at a speed of 280-320 r / min for 16-17 min. The heat preservation time is 28-32 min, and the stirring is carried out once every 10 min during the heat preservation period, with each stirring time lasting 25-35 s.

6. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the secondary processing step, the addition rate is ≤50g / min, and the heating temperature is 740-760℃.

7. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the secondary processing step, the stirring and mixing is carried out by electromagnetic stirring at a speed of 230-270 r / min for 8-12 min. The heat preservation time is 18-22 min, and argon gas is introduced for protection during the heat preservation period at a flow rate of 0.5-1 L / min.

8. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the three processing steps, the addition is made by crushing the Al-Sr alloy and Al-Ti alloy into 5-10mm particles before adding them; the heating temperature is 720-740℃; the stirring and mixing is done by electromagnetic stirring at a speed of 180-220r / min for 4-6min; and the holding time is 12-17min.

9. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, Before the temperature-controlled casting step, 0.1-0.2% of the mass of the third alloy melt is added to the third alloy melt as a refining agent. After electromagnetic stirring at a stirring rate of 200-250 r / min for 3-5 min, the mixture is allowed to stand for 8-12 min.

10. The method for preparing rare earth aluminum alloy for high-pressure casting thin-walled motor housings according to claim 3, characterized in that, In the temperature-controlled casting step, the temperature is controlled at 680-720℃. The high-pressure casting uses a die-casting machine with a pressure of 60-80MPa and an injection speed of 6.0-8.0m / s. Before high-pressure casting, the mold is preheated to 200-250℃.

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