Study on the assemblage of Y and Gd on microstructure and mechanical properties of hot extruded Mg-Al-Zn alloy

The microstructure and the mechanical properties of hot extruded Mg-Al-Zn alloy with the addition of Y and Gd were thoroughly investigated under two different conditions with and without aging treatments. The results showed that dynamic precipitation of Mg17Al12 phase occurred during hot deformation, and only Al2(Y,Gd) phase (no Al8Mn5 phase which was a common phase in Mg-Al-Zn alloy) was observed in the alloy. In addition, the basal texture intensity of Mg-Al-Zn alloy was weakened, which probably originates from both the promotion of nonbasal slip due to the addition of Y and Gd and the well-known particle-stimulated nucleation (PSN). Within the aged sample, there are less lamellar discontinuous precipitations (DPs), more globular DPs, and thinner continuous precipitation (CP) laths after Y and Gd addition. A new crystallographic orientation relationship (OR) between the β-Mg17Al12 precipitate and the α-Mg matrix was identified as (0001)m//(110)p and [011¯0]m//[1¯13]p. Finally, both tensile and compressive strengths are improved by the addition of Y and Gd, with the tension-compression yield asymmetry being reduced.