Effect of Long-Term Elevated Temperatures on Mechanical Properties of AlSi₁₀Mg

In this study, specimens of AlSi₁₀Mg fabricated by laser-powder bed fusion were exposed to 200, 220, 240, 260, 275, and 300 °C for various times to characterize the changes in mechanical properties over time. The duration of each isothermal treatment was varied from 15 min to 1000 h; one group of specimens was left in the “as-printed” condition as a control. The resulting microstructure and mechanical properties were characterized. Percent elongation, 0.2% offset yield strength, ultimate tensile strength, and hardness were measured and compared. The morphology of the silicon-rich phase was observed at several time and temperature conditions using optical and scanning electron microscopy. The strength and hardness decreased while the elongation increased 1) with increasing time at a given temperature and 2) with increasing temperature for any given time of exposure. The properties never reached a stable value for the durations of the exposures in this study, as indicated by the change in measurements after 300 °C and 1000-h exposure. The effects of time and temperature on mechanical properties are modeled well with the Larson–Miller parameter. The microstructure changes from having a fine network of silicon-rich precipitates to a coarse, equiaxed silicon particles with increased temperature of exposure.