The Bauschinger effect in a nitrogen-strengthened austenitic stainless steel

Abstract

The Bauschinger effect and yield strength anisotropy in an Fe-21wt.%Cr-6wt.%Ni-9wt.%Mn-0.29wt.%N austenitic stainless steel were measured after prestraining in uniaxial tension and in hemishells formed at 25 and 480 °C. The effect of stress relief heat treatment at 480 °C was also investigated. A new Bauschinger effect parameter, independent of process history, was introduced for this investigation and showed that the Bauschinger effect was generally reduced by both heat treating and warm forming. The reduction after warm forming was attributed to a decreased dislocation density and after stress relief heat treatment was attributed to strain aging. However, the interaction between the complex straining during hemishell formation and strain aging during heat treatment resulted in an increased Bauschinger effect for one direction in hemishells. Thus, warm forming is preferred to heat treating for reduction of the Bauschinger effect in complex shapes formed from alloys susceptible to strain aging.