【摘要】 本研究中，在A357合金中加入0.2%的Ni，采用光学显微镜和扫描电镜进行组织观察，对铸态、固溶态和时效态样品进行室温和250℃下拉伸实验，考察了Ni微合金化对A357组织和力学性能的影响。结果表明，0.2%Ni微合金化对A357合金铸态组织中枝晶α-Al相和共晶Si没有明显的影响，但降低了富Fe相的数量。铸态组织中出现富Ni相，固溶处理并不会使富Ni相发生明显的变化。从Ni微合金化前后合金在室温和250℃下屈服强度变化可知：对于室温强度，时效处理贡献显著，占支配地位；而对于高温强度，固溶处理的贡献占主导。Ni微合金能明显提高A357合金固溶态和固溶+时效态的室温和高温屈服强度，明显增强了固溶处理引起的室温与高温屈服强度增量，略微削弱了时效处理引起的室温与高温屈服强度增量。更多还原

【Abstract】 In this study,0.2wt.%Ni was added into A357 alloy to investigate the effect of Ni-microalloying on the microstructure and mechanical properties. Optical microscope and SEM was used to observe the microstructure.The mechanical properties of the samples with/without Ni-microalloying in as-cast,T4 and T6 states were examined at room temperature and at 250 ℃. The results indicates that addition of 0.2wt.% Ni in A357 alloy has no considerable influence on the dendritic α-Al phase and eutectic Si phase in as-cast microstructure. However,the amount of Fe-rich phase decreases. Ni-rich phase was observed in as-cast microstructure,but the solution treatment does not make it change greatly. From the changes of strength of the studied alloys in different states and at different testing temperatures,for room temperature strengthening,the contribution of aging treatment is significant and dominant;for high temperature strengthening,the contribution of solution treatment is dominant. Ni microalloy can considerably improve the yield strength of A357 alloy at room temperature and high temperature in T4 and T6 states,where,it greatly enhances the increment of yield strength at room temperature and high temperature caused by solution treatment and slightly weakens the increment of yield strength at room temperature and high temperature caused by aging treatment.更多还原