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 Al-2(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 beta-Mg17Al12 Precipitate and the alpha-Mg matrix was identified as (0001)(m)//(110)(p) and [01 (1) over bar0](m)//[(1) over bar 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. (C) 2015 Elsevier B.V. All rights reserved.