DEFORMATION-INDUCED MARTENSITIC CHARACTERISTICS IN 304-STAINLESS AND 316-STAINLESS STEELS DURING ROOM-TEMPERATURE ROLLING

The effect of grain size on the deformation-induced martensite (alpha' ) in 304 and 316 stainless steels (SS) during room-temperature rolling has been studied. Samples of four grain sizes of 52, 180, 229, and 28 5 mu m in 304 and three grain sizes of 77, 125, and 200 mu m in 316 SS have been rolled from 16 to 63 pet reduction in thicknesses to charac terize the microstructures during the rolling deformation. The amount of alpha' formed increases with increase in the emount of deformation in both SS for a given grain size. The volume fraction of martensite f ormed increases with a decrease in grain size in 304 SS, while the alp ha' martensite formation has been found to be grain size insensitive i n 316 SS. The volume fraction of alpha' formed in 304 SS is always hig her than that in 316 SS for a fixed percent reduction in thickness and grain size. This is attributed to the higher number of shear band int ersections observed in 304 SS, which are considered to be the nucleati on sites for the alpha' embryos. The lath martensite obtained at small true rolling strains changes to blocky type at higher true strains. T he morphology of alpha' formed has been discussed and its characterist ics obtained from rolling deformation have been compared with those ea rlier reported from the room-temperature tensile deformation.