T6热处理对铸造铝硅合金组织与硬度的影响

Effect of T6 Heat Treatments on Microstructure and Hardness Property of Cast Al-Si Alloy

通过金相组织分析和硬度测试,研究了铸造Al-9Si-2Cu-Mg合金在不同热处理工艺下的组织与硬度变化规律,并对铸造Al-9Si-2Cu-Mg合金的T6热处理工艺进行了优化。结果表明,铸造Al-9Si-2Cu-Mg合金经495℃固溶处理6 h后,合金的DSC曲线上几乎没有第二相的吸热峰,而合金微观组织中θ-Al_(2)Cu相发生了破碎,并几乎完全溶解;经过515℃与530℃下超过2 h的第二阶段固溶处理后,合金微观组织及其硬度均无明显变化;经过190℃保温4 h的人工时效处理后,合金的硬度趋于稳定,并且随着人工时效温度的升高,合金的硬度下降。最终优化后的T6热处理工艺为:第一阶段495℃固溶处理6 h;第二阶段515℃固溶处理2 h;第三阶段190℃人工时效4 h。

The T6 heat treatment process of cast Al-9Si-2Cu-Mg alloy was optimized by metallographic structure analysis and hardness test,after the changing rules of its microstructure and hardness affected by the T6 heat treatments was studied.The experimental results show that there is almost no endothermic peak on the DSC curve of the cast Al-Si alloy after solution treatment at 495℃ for 6 h,and the θ-Al_(2)Cu phase in its microstructure is broken and almost completely dissolved.After suffering from the second stage of solution treatment at 515℃ or 530℃ for more than 2 h,there is no obvious changes for the microstructure and the hardness of the alloy.The hardness of the samples tends to be stable after the artificial aging treatment at 190℃ holding for 4 h,and is decreased with the increase of the artificial aging temperature.Finally,the T6 heat treatment process was optimized as follows:At the first stage,solution treatment is performed at 495℃.for 6 h,at the second stage,solution treatment is performed at 515℃.for 2 h,and at the third stage,artificial aging is performed at 190℃ for 4 h.