Fig. 1. (a) and (b) are cross-sectional optical micrographs of as-cast AT72 alloys before and after SMAT deformation, respectively; (c) and (d) are cross-sectional optical micrographs of T4 and T6 AT72 alloys after SMAT deformation, respectively. “S” in each image represents the surface of the SMAT sample.

Fig. 2. (a) Bright-field TEM images of the layer that is 200-300 μm below the treated surface in T6 AT72 alloy; (b) SAED patterns with electron beam parallel to [1-210] zone axis of Mg matrix; (c) HRTEM image of phase boundary between α-Mg and precipitate; (d), (f), (h) are bright-field images under two-beam conditions; (e), (g), (i) are dark-field images under two-beam conditions.

Fig. 3. (a) Bright-field TEM image of the topmost layer with the thickness of 30 μm in the as-cast AT72 alloy after SMAT deformation; (b) is the SAED patterns of the particle circled in (a) with electron beam close to [011] of FCC crystal.

Fig. 4. HAADF-STEM images and EDS mapping results of the topmost layer with the thickness of 30 μm in SMATed cast AT72 alloy (Red, green and blue represent Mg, Al and Sn, respectively, and the overlapping images are at last.) (a) and (b) are recorded from two different specimens in order to verify this phenomenon. Rectangular marked area in (a) corresponds to EDS scanning area.

Fig. 5. Bright-field TEM image of the topmost layer with the thickness of 30 μm in the (a) T4 and (b) T6 AT72 alloys after SMAT deformation.