Microstructure and mechanical behavior of an AISI 304 austenitic stainless steel prepared by cold- or cryogenic-rolling and annealing

An AISI 304 austenitic stainless steel (ASS) with various ultrafine- or fine-grained structures was fabricated by cold- or cryogenic-rolling and annealing. The microstructure and mechanical properties of the ultrafine- or fine-grained ASS were investigated based on statistical data and physical metallurgy. The results showed that much more volume fraction of α′-martensite can be obtained by cryogenic-rolling in comparison with cold-rolling under a similar rolling strain, and ε-martensite was a medium to transform into α′-martensite finally during cryogenic-rolling. The deformed ASS with larger volume fraction of α′-martensite was beneficial to obtaining finer structure with a narrow distribution of grain sizes after the similar annealing process. The cycle annealing was a feasible method to make reverse transformation completely and to inhibit the structural coarsening simultaneously for the cold- or cryogenic-rolling ASS. The yield strength was enhanced by cryogenic-rolling and cycle annealing to be approximately 2.7 times higher than that of solution-treatment state. The tensile strength was not changed evidently, and the uniform strain was apparently decreased with reducing grain size. There is no significant relevance between the mechanical stability of austenite and average grain size for the ultrafine- or fine-grained ASS; however, their mechanical stability was less than that of solution-treatment state.