Characterization of β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy

Abstract As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1Nd-0.5Zr alloy, the β precipitate phase was assumed to be one of the main strengthening phases in peak-aged samples. This study aimed to determine the crystal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy using transmission electron microscopy and high-resolution electron microscopy. The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a =2.22 nm. The orientation relationship between the β precipitate phase and the α-Mg matrix was ( 1 ¯ 12 ) β / / ( 1 ¯ 100 ) α , [ 110 ] β / [ 0001 ] α . The β plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations. A single β plate often contained several domains of ( 1 1 ¯ 1 ) β twin-related variants. A composition of Mg 5 (Y 0.4 Gd 0.4 Nd 0.2 ) was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.