Effects of heat treatments on Microstructure and mechanical properties of Mg-4Y-4Sm-0.5Zr alloy

Microstructure and mechanical properties of Mg-4Y-4Sm-0.5Zr alloy during heat treatments were investigated. The eutectic phase dissolved into the matrix and there was no evident grain growth after solutionized at 798 K for 8 h. The alloy showed very fine scale precipitates in the grains and along the grain boundaries after ageing at 473 K for 16 h. And the ultimate tensile strength of 348 MPa, yield strength of 217 MPa and elongation of 6.9% were attained in this under-aged state. The elongation of alloy greatly decreased, and the ultimate tensile strength decreased respectively with increasing the ageing time, for increasing amount and coalescence of the precipitates along the grain boundaries. The mechanical properties of the alloy could hold up to 473 K, and decreased steeply at temperatures higher than 523 K, for the softening of the precipitates and activation of non-basal slip systems.