Microstructures and Tensile Properties of Mg-6Gd-3Y-1.4Zn-0.4Zr Alloys

Microstructures and tensile mechanical properties of Mg–6Gd–3Y–1.4Zn–0.4Zr (wt.%) alloy were systematically studied. Three phases were found in the as-cast specimen: α-Mg, Mg5(GdYZn), Mg12(GdY)Zn. The long-period stacking order (LPSO) structure was found in the alloy, which is the phase of Mg12(GdY)Zn. Two LPSO structures with different images were found in the homogenized alloys: the block-shaped ones at grain boundaries and needle-like ones in the inner grains. The homogenized Mg–6Gd–3Y–1.4Zn–0.4Zr (wt.%) alloy was subjected to multidirectional forging (MDF) at 480°C. It was shown that the average grain size decreased to ~5.2μm after 9 passes with the cumulative strain of 2.7. The ageing hardening behavior of as-forged specimens at 200°C has been investigated. Peak hardness was obtained after 26 h, with a value of 110 HV. The ultimate tensile strengths of the as-forged and peak-aged alloys were 398 MPa and 431 MPa, the yield strengths were 351MPa and 398MPa, and the elongations were 11.24% and 8% respectively.