Eighty percent heavy cold thickness reduction and reversion transformation in the temperature range 700-950 • C for 60 s were performed to obtain the reverted ultrafine-grained (UFG) structure in 304 austenitic stainless steel. Through mechanical property experiments and transmission electron microscopy (TEM) of micro deformation of the UFG austenite structure, the tensile fractographs showed that for specimens annealed at 700-950 • C, the most frequent dimple sizes were approximately 0.1-0.3 µm and 1-1.5 µm. With the increase in annealing temperature, the dimple size distribution of nano-sized grains turned to micron-size. TEM micro deformation experiments showed that specimens annealed at 700 • C tended to crack quickly. In the grain annealed at 870 • C, partial dislocations were irregularly separated in the crystal or piled up normal to the grain boundaries; stacking faults were blocked by grain boundaries of small grains; twins held back the glide of the dislocations. In the grain annealed at 950 • C, the deformation twins were perpendicular to ε martensite. Fine grain was considered a strengthening phase in the UFG structure and difficult to break.

A constant amount of Ge was deposited on strained GexSi1−x layers of approximately the same thickness but with different alloy compositions, ranging from x=0.06 to x=0.19. From their atomic-force-microscopy images, we found that both the size and density of Ge islands increased with the Ge composition of the strained layer. By conservation of mass, this implies that these islands must incorporate material from the underlying strained layer.

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