基于CALPHAD 计算的铸造Al-Si-Cu-Mg 合金热处理工艺优化研

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 Al₂ 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. 8 μm. 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.