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

摘要

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.