Atomic-resolution investigation of Y-rich solid solution with an invariable orientation in Mg−Y binary alloy

After solid solution and aging treatment, Mg−10 wt.% Y alloys were characterized using high angle annular dark field scanning transmission electron microscopy (HAADF−STEM) technique. An aggregation of yttrium (Y) can be identified as a type of Y-rich solid solution (YSS) based on observations from [ 0001 ] Mg and [ 11 2 ¯ 0 ] Mg directions. The YSS is generally in nanometer size and crystalizes in face-centered cubic (FCC) structure with lattice parameter a = 5.20 A. Moreover, an invariable orientation relationship between YSS and Mg matrix can be determined. The existence of interfacial mismatch reveals that the interface between YSS and Mg matrix is semi-coherent. It theoretically suppresses the coarsening of YSS.