Multiple, comparative heat treatment and aging schedules for controlling the microstructures and mechanical properties of laser powder bed fusion fabricated AlSi10Mg alloy

Abstract

In this investigation, the optimization of mechanical properties with thermal post-processing treatments was analyzed across a wide range of variants. A major aspect of additive manufacturing is the correlation between heat treatments and the effects on the mechanical properties and microstructure of the printed materials. Therefore, the present paper describes a comprehensive overview of post-process heat treatments for Laser Powder Bed Fusion fabricated AlSi10Mg alloy consisting of stress relief anneals at 190 ̊C and 285 ̊C for 2 h, hot isostatic pressing at 515 ̊C for 3 h, hot isostatic pressing + T6 treatment for 6 h, and final aging of each of these conditions at 177 ̊C for up to 1000 h. This has resulted in 40 experimental variants: 20 in the vertical and 20 in the horizontal tensile direction. After tensile testing, the resulting mechanical properties (ultimate tensile strength, yield strength, and elongation) and stress–strain curves are analyzed for comparison between all variants. Ultra-fine cellular, micro dendritic structures (0.6–1.2 μm) along with melt-band structures dominated the asbuilt and stress relief anneal conditions. In contrast, hot isostatic pressing and hot isostatic pressing + T6 conditions were dominated by ~10 μm, equiaxed, recrystallized grain structures and pseudo-eutectic silicon particles with varying sizes and size distributions. Microhardness and fractography results also corresponded to their specific heat treatment and microstructure. The comparison and correlation of the heat treatments are presented to help advance the selection of design strategies for high performance applications.

Keywords

• AlSi10 Mg alloy
• Laser Powder Bed Fusion
• Heat treatments
• Microstructure analysis
• Mechanical properties
• Hardness