Abstract:The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY (x=0, 0.5, 1.0, 1.5 and 2.0, mass fraction, %) (ZCK630+xY for short in this study) alloys were investigated by means of OM, XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced (from 57 μm to 39 μm) by Y addition. The analysis of XRD indicates the existence of I-phase (Mg₃Zn₆Y) and W-phase (Mg₃Zn₃Y₂) in ZCK630 alloys with Y addition. The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition, which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.

Key words: Mg-Zn-Cu-Zr alloy; yttrium; microstructure; mechanical property