The microstructure and mechanical properties of Mg-3Nd-0.2Zn-0.4Zr（wt.%）（NZ30 K） alloy in as-cast

solution-treated and aged condition were investigated. As-cast NZ30K alloy consisted of α-Mg matrix separated by coarse inter-granular Mg12Nd compounds. After solution treatment

the inter-granular Mg12Nd compounds disappeared and lots of fine Zr-containing particles distributed at grain interiors. During aging process

fine plate-like phases precipitated at the prismatic planes of α-Mg matrix

which strengthened the alloy

while the the Zr-containing particles were still at grain interiors. Different aging process led to different precipitates. The precipitates are probably β″ meta-stable phases with DO19 structure in 200 ℃ peak-aged alloy

while in 250 ℃×10 h aged alloy they are mainly β’ meta-stable phases with fcc structure. 200℃ peak-aged NZ30K alloy had the best mechanical properties at room temperature and yield strength

ultimate tensile strength and elongation are 142 MPa

305 MPa

11%

respectively. NZ30K alloy had different fracture pattern in different thermal conditions: as-cast alloy mainly fractured inter-granularly; solution-treated and 200 ℃ peak-aged alloy mainly fractured trans-granularly; 250 ℃×10 h aged alloy fractured in a mixture pattern.