Intermetallic phases in Mg-Co-Y alloys

The microstructural details and phase evolution of the as-cast and annealed Mg88Co5Y7(at.%) alloys were characterized by means of electron microscopies. Two new crystalline phases were revealed in the Mg-Co-Y alloys. They are hexagonal with composition of about Mg70-73Co5Y22-25 (Mg3(Co,Y)) (a = 1.04 nm, c = 2.25 nm, P63/mmc) and face-centered cubic with a composition of about Mg15Y21Co64 (MgYCo4) (a = 0.707 nm, F 4¯3m), isostructural to MgSnCu4. In addition, a new crystallographic orientation relationship between Mg and Mg24Y5 has been observed.