Strain-induced submicrocrystalline grains developed in austenitic stainless steel under severe warm deformation

Strain-induced grain evolution in a 304 type austenitic stainless steel has been studied in multiple compression with the loading direction being chan ged in each pass. The tests were carried out to total strains above 6 at 87 3 K (0.5T(m)) at a strain rate of about 10(-3) s(-1). Multiple deformation promotes the rapid formation of many mutually crossing subboundaries becaus e various slip systems operate from pass to pass. The gradual rise in misor ientations across dislocation subboundaries with increasing strain finally leads to the evolution of very fine grains with large-angle boundaries. It is concluded that a new grained structure can result From a kind of continu ous reaction during deformation, namely continuous dynamic recrystallizatio n. Such deformation-induced grains are characterized by relatively low dens ities of dislocations, and considerable lattice curvatures developed in the ir interiors. The latter observations suggest that high elastic distortions are developed in the grain interiors and so such strain-induced grain stru ctures are in a non-equilibrium state.