Understanding microstructural evolution and mechanical behaviour of AlSi10 alloy: insights from powder bed fusion laser beam and high pressure die casting processes

This investigation is focused on comprehending the impact of a broad spectrum of cooling rates ranging from 10^-2 to 10^5 K/s on the microstructure and mechanical properties of AlSi10 alloys. The AlSi10 alloys were manufactured using high pressure die casting (HPDC) and powder bed fusion-laser beam (PBF-LB) processes. A detailed comparison of microstructures was conducted to understand variations in tensile and bending properties. Subsequently, heat treatment process-property maps were formulated for the PBF-LB AlSi10Mg alloy to fine-tune the differences identified in the tensile properties of PBF-LB and HPDC alloy. These maps serve as valuable tools for advancing rapid prototyping application. Furthermore, an in-depth microstructure analysis of both alloys facilitated the development of a kinetic Al-Si phase diagram, delineating the extent of solute trapping and eutectic temperature depression as the cooling rate increases. The higher cooling rate associated with the PBF-LB process resulted in a refined and interconnected Al-Si eutectic microstructure, contributing to back stress generation during tensile deformation. This, in turn, resulted in elevated yield strength and strain hardening coefficient. Therefore, a novel strengthening model is proposed for the PBF-LB AlSi10Mg alloy, encompassing both conventional strengthening and back stress strengthening mechanisms.