Microstructure and mechanical properties of as-cast and different heat treated Mg
x2013;3Nd
x2013;0.2Zn
x2013;0.4Zr (wt.%) (NZ30K) alloys were investigated. The as-cast alloy was comprised of
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magnesium matrix and Mg
12Nd eutectic compounds. After solution treatment at 540 °C for 6 h, the eutectic compounds dissolved into the matrix and small Zr-containing particles precipitated at grain interiors. Further aging at low temperatures led to plate-shaped metastable precipitates, which strengthened the alloy. Peak-aged at 200 °C for 10
x2013;16 h, fine β″ particles with DO
19 structure was the dominant strengthening phase. The alloy had ultimate tensile strength (UTS) and elongation of 300
x2013;305 MPa and 11%, respectively. Aged at 250 °C for 10 h, coarse β′ particles with fcc structure was the dominant strengthening phase. The alloy showed UTS and elongation of 265 MPa and 20%, respectively. Yield strengths (YS) of these two aged conditions were in the same level, about 140 MPa. Precipitation strengthening was the largest contributor (about 60%) to the strength in these two aged conditions. The hardness of aged NZ30K alloy seemed to correspond to UTS not YS.