Formation of β′ phase in LPSO structures in an Mg88Co5Y7 alloy

Abstract

Formation of β′ phase in long-period stacking ordered (LPSO) structures in an Mg 88 Co 5 Y 7 (at.%) alloy after aging at 200 °C for 24 h or electron beam (EB) irradiation has been studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). β ′ phase was precipitated only in the Mg matrix but not in LPSO structures after aging at 200 °C for 24 h. LPSO structure containing stacking defects transforms into the β′ -long phase during EB irradiation, which plays a key role in accelerating solute atoms’ diffusion. New complex β ′(LPSO) structures formed in the alloy after EB irradiation, such as β ′(12H) structure with an orthorhombic lattice (Mg 7 Y, Cmcm, a = 2 a 0 = 0.642 nm, b = 4 3 a 0 = 2.27 nm, c = 6 c 0 = 3.12 nm).