Investigation of the Quench Sensitivity of an AlSi10Mg Alloy in Permanent Mold and High-Pressure Vacuum Die Castings.

The quench sensitivities of an AlSi10Mg alloy in permanent mold (PM) and high-pressure vacuum die (HPVD) castings were investigated with time-temperature-transformation and time-temperature-property diagrams using an interrupted quench technique. The quench-sensitive temperature range of the HPVD casting sample is 275-450 °C, and its nose temperature is 375 °C. The quench-sensitive range of the PM casting sample is 255-430 °C, and the nose temperature is 350 °C. The mechanical strength versus the cooling rate in both casting samples were predicted via a quench factor analysis and verified experimentally. The critical cooling rate of the HPVD casting sample is 20 °C/s whereas it is 17 °C/s for the PM casting sample. With a shorter critical time, higher nose temperature, and higher critical cooling rate, the HPVD casting sample exhibits a higher quench sensitivity than the PM casting sample. The differences in the quench sensitivities of the AlSi10Mg alloy due to the different casting processes is explained via the different precipitation behavior. At the nose temperature, coarse β-MgSi precipitates mainly precipitate along the grain boundaries in the HPVD casting sample, whereas rod-like β-MgSi precipitates distribute in the aluminum matrix in the PM casting.