Effect of heat treatment on the microstructures and mechanical properties of the sand-cast Mg–2.7Nd–0.6Zn–0.5Zr alloy

Abstract

The tensile testing bars of the Mg–2.7Nd–0.6Zn–0.5Zr (wt.%) alloy were prepared by sand casting. The effect of solution temperature and aging time on the microstructures and mechanical properties were investigated. The as-cast alloy was composed of α magnesium matrix and Mg12Nd eutectic compounds. After solution treatment at 500 °C for 18 h, the volume fraction of eutectic compounds decreased from ∼7.8% to ∼2.3%, and some small Zr-containing particles were observed to precipitate at grain interiors. As the solution temperature increased to 525 °C for 14 h, most of the eutectic compounds dissolved into the matrix. Peak-aged at 200 °C for 12 h, fine β″ particles was the dominant strengthening phase. The yield strength, ultimate tensile strength and elongation in the peak-aged condition were 191 MPa, 258 MPa and 4.2%, respectively. Moreover, the Mg–2.7Nd–0.6Zn–0.5Zr alloys under different heat treatment conditions exhibited different tensile fracture modes.