THE EFFECT OF STRESS-STATE ON THE LARGE-STRAIN INELASTIC DEFORMATION-BEHAVIOR OF 304L STAINLESS-STEEL

In metals, large strain inelastic deformation processes arch as the fo rmation of a preferred crystallographic orientation (crystallographic texture) and strain hardening processes such as the formation and evol ution of dislocation substructures depend on stress-state. Much of the current large strain research has focused on texture. Crystallographi c texture development and strain-hardening processes each contribute t o the overall material behavior, and a complete description of large s train inelastic material response should reflect both. An investigatio n of the large strain behavior of 304L stainless steel (SS 304L) subje cted to compression, torsion, and sequences of compression followed by torsion and torsion followed by tension is reported. This paper focus es on the stress-state dependence of strain-hardening processes as wel l as the relative effect such processes have on the overall material b ehavior, To characterize these processes, transmission electron micros copy (TEM) as well as magnetization investigations were conducted at d ifferent strain levels and under different deformation modes. The gamm a --> alpha' martensitic transformation which occurs in this material was found to be related to both the strain level and stress state. Dis location substructures in the form of Taylor lattices dense dislocatio n walls, and microbands were also present. The ramifications of using a thin-walled tubular torsion specimen were also explored.