Effect of heat treatment parameters on microstructure, defects, and properties of Al-16Si-6Cu automotive shift fork: quantitative evaluation perspective

The current study investigated the effect of heat treatment parameters, including solution treatment temperature (STT), time, and quench rate, on the microstructure, defects, and hardness of an Al-16Si-6Cu Shift fork die-cast alloy. The changes in primary silicon particle (PSP) features were examined quantitatively by optical microscopy, coupled with image analysis and SEM equipped with EDS. The biggest PSPs (27 ± 8 µm) and the highest area fraction (23%) were found in the sample solution treated at 470°C and cooled in the furnace. The hardness value increased in heat-treated samples slightly (140–148 BHN). A lower STT (420°C) and a lower ageing time (1 h) are suitable conditions for the heat treatment of an Al-16Si-6Cu die-cast alloy, in which a lower pore area fraction, 1.18, smaller pore, 4.5 μm, along with finer primary silicon, 9.5 ± 3 μm, with higher circularity, 0.38 ± 0.04, was achieved.