Effects of alloying elements on mechanical properties and deformation-induced martensite transformation in Cr-Mn-Ni austenitic stainless steels

Abstract

The effects of alloying elements on structures, mechanical properties and deformation-induced martensite transformation were investigated in five types of Cr-Mn-Ni austenitic stainless steels: 14%Cr-1%Ni-10%Mn-0.13%N, 15%Cr-4%Ni-8%Mn-0.05%N, 15%Cr-4%Ni-8%Mn-0.12%N, 17%Cr-5%Ni-1%Mn-0.10%N and 17%Cr-6.5%Ni-4%Mn-0.05%N. The relationships between the compositions and their properties were discussed. The constitutional diagram using Cr and Ni equivalents as Schaeffler's diagram did not correspond to the observed structures of cold rolled and annealed sheets in Cr-Mn-Ni stainless steels. The constitutional diagram of Cr-Mn-Ni stainless steels was described using the equations for the calculated ferrite content and the Ms temperature. The effects of alloying elements on 0.2% proof stress in Cr-Mn-Ni stainless steels was almost equal to that in Cr-Ni stainless steels. The effect of Mn on austenite stability, which reveals the ease of deformation-induced martensite transformation, in Cr-Mn-Ni stainless steels was larger than that in Cr-Ni stainless steels. Therefore, the new Ni equivalent which exhibits austenite stability was attained by regression analysis between deformation-induced martensite transformation contents and compositions. A high correlation between this Ni equivalent and the formability of Cr-Mn-Ni stainless steels was recognized.