基于CALPHAD计算的铸造Al-Si-Cu-Mg合金热处理工艺优化研究

Optimization of Heat Treatment Process of Al-Si-Cu-Mg Cast Alloy Based on CALPHAD Calculation

热处理工艺参数的优化在铸造Al-Si-Cu-Mg合金组织性能调控方面扮演着重要角色。本工作以铸造Al-Si-Cu-Mg合金为研究对象,利用热力学计算和实验相结合的方法对合金的热处理工艺参数进行优化设计。热力学计算和差示扫描量热法(DSC)结果表明,Al-Si-Cu-Mg合金低熔点共晶相Al_(2)Cu相的形成温度是501℃,并且通过热力学软件动力学模块计算可知Si、Mg和Cu元素在495℃固溶温度下5 h内能够达到均匀化扩散。随着固溶温度的升高和时间的延长,共晶硅发生熔断、球化和粗化长大现象。另外,显微硬度受固溶程度以及共晶硅形貌的影响,在固溶过程中随着固溶温度的升高和时间的延长先升高后降低。当固溶温度为495℃、固溶时间为12 h时,显微硬度达到最大值(70.8±1.0)HV,球状共晶硅的Feret直径为2.8μm。在170℃下对合金进行时效处理时,合金的显微硬度逐渐升高,当时效时间为5 h时达到峰时效,其显微硬度达到(119.0±5.7)HV。

The optimization of heat treatment process parameters plays an important role in the regulation of microstructure and properties of Al-Si-Cu-Mg cast alloy.In this work,the heat treatment process parameters of Al-Si-Cu-Mg cast alloy were optimized by the combination of thermodynamic calculation and experiment.The results of thermodynamic calculation and differential scanning calorimetry(DSC)show that the formation temperature of low melting point eutectic Al_(2)Cu phase is 501℃,and the calculation of thermodynamic software dynamics module shows that Si,Mg and Cu elements reach homogenization diffusion within 5 h at 495℃.With the increase of solution temperature and time,eutectic Si gradually fragments,spheroidizes and coarsens.In addition,the microhardness is affected by the degree of solution heat treatment and the morphology of eutectic Si.During the solution heat treatment,the microhardness first increases and then decreases with the increase of solution temperature and time.When the solution temperature is 495℃and the solution time is 12 h,the microhardness reaches the maximum value of(70.8±1.0)HV,and the Feret diameter of spherical eutectic Si is 2.8μm.When the alloy is aged at 170℃,the microhardness of alloy increases gradually,and reaches the peak aging when the aging time is 5 h,and the microhardness reaches(119.0±5.7)HV.