Heat-treatment-free Al-Mg series high-toughness die-casting aluminum alloy

Abstract

The invention discloses a heat-treatment-free Al-Mg series high-toughness die-casting aluminum alloy which comprises the following components in percentage by weight: 3-9% of Mg, 0-2.6% of S , 0.1-2.6% of Mn, 0.1-0.2% of T and less than or equal to 0.05% of auxiliary added trace elements besides aluminum, the auxiliary added trace elements are one or more of Zn, Cu and Be, the specific alloy components are A < 1-7 > Mg-3Si-Mn-T alloy, and on the basis of an aluminum-magnesium alloy, the Al-Mg series high-toughness die-casting aluminum alloy is prepared from the Al-Mg series high-toughness die-casting aluminum alloy, the Al-Mg series high-toughness die-casting aluminum alloy is prepared from the Al-Mg series high-toughness die-casting aluminum alloy. The mechanical property of the as-cast aluminum alloy can reach the performance standard of castings for automobiles through the alloy proportion of the added trace silicon and manganese elements.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly to a heat-treatment-free Al-Mg series high-strength and tough die-casting aluminum alloy. Background Art

[0002] The integrated die-casting technology is a new revolution in die-casting technology. Using the integrated die-casting technology, multiple original independent castings and stampings can be integrated into a complete casting. On the basis of omitting subsequent processes such as welding and riveting of multiple original parts, the one-time forming of large and complex castings can be completed. The integrated die-casting technology has obvious advantages in improving production efficiency, reducing weight, and lowering costs. The core of its technology lies in the design and manufacture of large die-casting machines, the development of heat-treatment-free materials, the design of large-size die-casting molds, and the optimization of die-casting processes.

[0003] At present, the heat-treatment-free aluminum alloys for integrated die-casting mainly include two major alloy series, namely the Al-Si series and the Al-Mg series. Although the Al-Si series alloys have better casting properties, the Al-Mg alloys have also become another type of heat-treatment-free aluminum alloy material that has attracted much attention at present due to their excellent plasticity and toughness and good corrosion resistance. The Al-Mg alloys in the traditional heat-treatment state have problems of poor casting properties and machinability, which limit their application in high-performance castings. At present, the comprehensive properties of the materials are mainly optimized by adjusting the alloy element composition and introducing micro-alloying methods.

[0004] Since the Al-Mg alloy cannot form nano-strengthening phases after heat treatment, it was once classified as a non-heat-treatable alloy. This characteristic makes this series of alloys usually used in the as-cast state. Table 1 lists the chemical compositions of several current heat-treatment-free die-casting alloys of the Al-Mg series.

[0005] The C446F alloy (i.e., 560) is an early-developed non-heat-treatable Al-Mg series die-casting alloy, which was once applied to the inner panel of the car door. The wall thickness of the part is about 2-3 mm, so as to achieve a weight reduction of 5.5 kg for a single car door. Although this type of alloy has excellent mechanical properties, such as high strength and good wear resistance, its solidification temperature range is relatively wide, resulting in a large temperature gradient and stress concentration during solidification, thus increasing the risk of hot crack formation. Especially when die-casting complex structural parts, such as parts with complex geometric shapes, uneven wall thickness distribution, or sharp transition regions, this problem is particularly prominent. Therefore, for die-casting parts with complex structures or significant thickness changes, such alloys have certain limitations in process adaptability and are difficult to be the most preferred material selection scheme.

[0006] Alloys A152 and A153 are developed by Alcoa on the basis of alloy C446F. By adding an appropriate amount of Si element, the solidification temperature range of the alloy is narrowed, thus effectively improving the hot cracking performance. By introducing about 1.3 wt.% of Si element into the alloy, its solidification temperature range is effectively reduced from the original wide range to about 40 °C, significantly reducing the accumulation of thermal stress during solidification, and thus significantly improving the hot cracking resistance of the alloy. This series of alloys also realizes precise control of properties by adjusting the Mg content to meet the mechanical property requirements of different die-cast parts.

[0007] Magsimal 59 alloy, with the composition of AlMg5Si2Mn, is a non-heat-treatable die-casting aluminum alloy. Similar to A152 / 153 alloys, Magsimal 59 alloy also contains about 2 wt.% of Si element, which helps to improve the hot cracking resistance of the alloy and the fluidity of the melt during die-casting. Since the Si content in this alloy is much lower than the eutectic composition of Al-Si alloys, its overall solidification characteristics are significantly different from those of traditional Al-Si alloys, resulting in relatively poor casting performance. For example, it is inferior to eutectic or near-eutectic Al-Si alloys with high Si content in terms of fluidity, filling ability and crack resistance, which is particularly prominent when die-casting complex thin-walled structural parts. In addition, this alloy has high requirements for melting process conditions and is easily affected by melt temperature, atmosphere control and inclusions, increasing the process difficulty and quality control cost in actual production. It should be noted that the eutectic structure of Magsimal 59 alloy is relatively scarce, its mechanical properties are closely related to the dendrite spacing of α-Al, and the wall thickness of the casting has a significant impact on the solidification rate of the alloy. A thinner wall thickness corresponds to a higher cooling rate, which can obtain a denser tissue structure; while in the thick-walled area, due to slow cooling, it is easy to cause coarse dendrites and local property fluctuations.

[0008] Castaduct 42 alloy is a non-heat-treatable die-casting alloy of the Al-Mg-Fe system. The content of Fe element in this alloy is close to the critical composition of the Al-Fe eutectic reaction (about 2 wt.% Fe), and theoretically has good fluidity, which is particularly beneficial for die-casting complex structural parts, helping to improve the filling ability and reduce the occurrence of defects such as cold shuts and misruns. Although the regulation of Fe content theoretically helps to improve the fluidity of the melt, it is still uncertain whether the overall casting performance is better than that of the widely used C446F alloy, and further verification is needed through systematic process tests and performance evaluations.

[0009] The JDA2x alloy, including SJTU-Al-Mg-Cu-Mn and SJTU-Al-Mg-Si-Mn, is a non-heat-treatable die-cast aluminum alloy developed by Shanghai Jiao Tong University. Its main goal is to improve the yield strength of the material while ensuring good toughness. For the Al-Mg-Si-Mn alloy, with the increase in the content of magnesium (Mg), the yield strength and fatigue limit of the material increase to a certain extent, but the elongation decreases significantly. Therefore, in this alloy, by increasing the content of magnesium (Mg) and silicon (Si) elements and regulating their ratio, and introducing alloying elements such as titanium (Ti), zirconium (Zr), and vanadium (V) to improve the microstructure, and using a Re / Ca composite modifier to refine the eutectic silicon, excellent mechanical properties with a yield strength exceeding 180 MPa and an elongation exceeding 10% are obtained. The SJTU-Al-Mg-Cu-Mn alloy enhances its properties by adding copper (Cu) elements and introduces rare earth elements (such as yttrium (Y), erbium (Er), and cerium (Ce)) to refine the Al2CuMg phase, ultimately achieving comprehensive mechanical properties with a yield strength greater than 180 MPa, a tensile strength exceeding 320 MPa, and an elongation exceeding 8%.

[0010] The present invention proposes a new type of Al-Mg-based alloy, which can be used as a heat-treatment-free aluminum alloy for integrated die-casting molding. At the same time, during the melting process, the defined range of iron can be appropriately increased (0.15 - 0.50 wt.%), and the morphology and structure of the Fe phase can be controlled by alloying methods, which can increase the application ratio of recycled aluminum in the raw materials for integrated die-casting. Summary of the Invention

[0011] The purpose of the present invention is to solve the deficiencies existing in the prior art and propose a heat-treatment-free Al-Mg-based high-strength and high-toughness die-cast aluminum alloy.

[0012] To achieve the above purpose, the present invention adopts the following technical solutions:

[0013] A heat-treatment-free Al-Mg-based high-strength and high-toughness die-cast aluminum alloy, with Mg 3 - 9 wt.%, Si 0 - 2.6 wt.%, Mn 0.1 - 2.6 wt.%, Ti 0.1 - 0.2 wt.%, and the trace elements added as auxiliaries ≤ 0.05 wt.%.

[0014] The above technical solution further includes:

[0015] The specific alloy composition is: Al-7Mg-3Si-Mn-Ti alloy.

[0016] The trace elements added as auxiliaries are one or more of Zn, Cu, and Be.

[0017] The as-cast tensile strength of the Al-7Mg-3Si-Mn-Ti alloy is 316.7 MPa, the yield strength is 185.4 MPa, the elongation is 10.7%, and the microhardness value is 113.4 HV.

[0018] The as-cast structure of the alloy consists of α-Al phase, (α-Al + Mg2Si) eutectic phase, Al3Ti phase, and Al(Fe,Mn)Si phase.

[0019] The fracture mode of the as-cast Al-7Mg-3Si-Mn-Ti alloy at room temperature is a ductile-brittle mixed fracture.

[0020] The present invention has the following beneficial effects:

[0021] Based on the aluminum-magnesium alloy, through the alloy ratio with the addition of trace amounts of silicon and manganese elements, the mechanical properties of the as-cast aluminum alloy meet the performance standards of automotive castings. Description of the Drawings

[0022] Figure 1 It is the first experimental diagram of a heat-treatment-free Al-Mg series high-strength and tough die-casting aluminum alloy proposed by the present invention;

[0023] Figure 2 It is the second experimental diagram in the present invention;

[0024] Figure 3 It is the third experimental diagram in the present invention;

[0025] Figure 4 It is the fourth experimental diagram in the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment

[0028] Except for aluminum, Mg is 3 - 9 wt.%, Si is 0 - 2.6 wt.%, Mn is 0.1 - 2.6 wt.%, Ti is 0.1 - 0.2 wt.%, and the trace elements added as auxiliaries ≤ 0.05 wt.%. The trace elements added as auxiliaries are one or more of Zn, Cu, and Be.

[0029] The specific alloy composition obtained is: Al-7Mg-3Si-Mn-Ti alloy

[0030] The as-cast tensile strength of the Al-7Mg-3Si-Mn-Ti alloy is 316.7 MPa, the yield strength is 185.4 MPa, the elongation is 10.7%, and the microhardness value is 113.4 HV. The as-cast microstructure of the alloy consists of α-Al phase, (α-Al+Mg2Si) eutectic phase, Al3Ti phase, and Al(Fe,Mn)Si phase. The Mg2Si phase exists in spherical, near-spherical, and short rod-like shapes, is relatively evenly distributed, and has relatively small sizes, being the strengthening phase with the largest volume ratio. The Al3Ti phase is mainly strip-shaped, and the Al(Fe,Mn)Si phase is distributed in the form of polygons and particles within the grains and at the grain boundaries. The room-temperature fracture mode of the as-cast Al-7Mg-3Si-Mn-Ti alloy is a ductile-brittle mixed fracture.

[0031] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An as-cast heat-treatable Al-Mg series high-strength and tough die-casting aluminum alloy, characterized in that, In addition to aluminum, it also includes: Mg 3-9 wt.%, Si 0-2.6 wt.%, Mn 0.1-2.6 wt.%, Ti 0.1-0.2 wt.% and trace elements added as auxiliary ≤0.05 wt.%.

2. The heat-treatment-free Al-Mg series high-strength and tough die-casting aluminum alloy according to claim 1, characterized in that, The specific alloy composition is: Al-7Mg-3Si-Mn-Ti alloy.

3. An as-cast heat-treatable Al-Mg series high-strength and tough die-casting aluminum alloy according to claim 1, wherein, The trace elements added as auxiliary are one or more of Zn, Cu and Be.

4. A heat-treatment-free Al-Mg series high-strength and tough die-casting aluminum alloy according to claim 1, characterized in that, The as-cast tensile strength of the Al-7Mg-3Si-Mn-Ti alloy is 316.7 MPa, the yield strength is 185.4 MPa, the elongation is 10.7%, and the microhardness value is 113.4 HV.

5. An as-cast heat-treatable Al-Mg series high-strength and tough die-cast aluminum alloy according to claim 1, characterized in that, The as-cast microstructure of the alloy consists of α-Al phase, (α-Al+Mg2Si) eutectic phase, Al 3Ti phase, and Al(Fe,Mn)Si phase.

6. The as-cast high-strength and tough Al-Mg series die-casting aluminum alloy according to claim 1, characterized in that The room-temperature fracture mode of the as-cast Al-7Mg-3Si-Mn-Ti alloy is a ductile-brittle mixed fracture.

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