不同慢压射速度高真空压铸制备rA390铝合金及其性能表征

摘要

The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390 alloy at different slow shot speeds were evaluated. Plate-shaped specimens of hypereutectic A390 aluminum alloy were produced on a TOYO BD-350V5 cold chamber die casting machine incorporated with a self-improved TOYO vacuum system. According to the results, the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling. Meanwhile, tensile properties of vacuum die castings were deteriorated by the porosity content. In addition, the average primary silicon size decreased from 23 to 14 μm when the slow shot speed increased from 0.05 to 0.2 m/s, which has a binary functional relationship with the slow shot speed. After heat treatment, microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved intoα(Al) matrix. Furthermore, the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment.%对真空辅助不同慢压射速度条件下制备的A390高硅铝合金铸件组织及力学性能进行研究.在装备自行改进TOYO真空系统的TOYO BD-350V5型冷室压铸机上制备片状A390压铸件.结果表明,型腔中的真空度与初始充模阶段慢压射速度呈线性关系.拉伸试验结果表明,试样的拉伸强度随试样内部的孔洞含量升高而降低.另外,当慢压射速度从0.05 m/s增大到0.2 m/s时,初晶Si尺寸由23μm降低到14μm,初晶Si的平均尺寸与慢压射速度存在二元次数关系.经热处理后,初始铸态α(Al)边界上的Al2Cu因融入Al基体中而大幅减少,并且针状或带状共晶Si球化.断裂形貌表明,断裂形式由热处理前的脆性沿晶断裂转变为热处理后的含有大量韧窝的韧性穿晶断裂.