Effects of the microstructure and precipitation hardening on the thermal expansion behavior of ZK60 magnesium alloy

In this study, the thermal expansion behavior of ZK60 magnesium alloy was investigated under different precipitation hardening and extrusion conditions. The alloy samples were subjected to precipitation hardening at temperatures of 125, 175, and 225 degrees C for 6, 12, 18, 24, and 30 h, and extrusion process at ratios of 1:6, 1:8, 1:12, and 1:18 to evaluate the effects of volume fraction of precipitates and grain size on the thermal expansion behavior of the alloy. Microstructure characterizations showed that the precipitates with needle and cloudy morphologies and uniform distribution were formed in the samples. It was revealed that the size and volume fraction of the precipitates were highly dependent on the process conditions. Microhardness measurement results demonstrated that the sample treated at 175 degrees C for 12 h submitted the highest hardness. Also, the dilatometry test results confirmed that the presence of precipitates resulted in a decrease in the coefficient of thermal expansion; so that the lowest value was obtained for the sample aged at 175 degrees C. Furthermore, it was concluded that the matrix grain size and volume fraction of the precipitates affected the thermal expansion behavior of the ZK60 magnesium alloy. (c) 2021 Elsevier B.V. All rights reserved.