Effect of deformation-induced martensitic transformation on the plastic behavior of metastable austenitic stainless steel

Abstract

The effect of deformation-induced martensite on the tensile behavior of metastable austenitic stainless steel has been investigated on a AISI Type 301 stainless steel containing a small amount of copper using the X-ray diffraction technique and transmission electron microscopy. The formation of martensite during tensile deformation increases the accumulation of dislocations in the austenitic phase, which leads to the enhanced work-hardening rate of this type of steel. The linear relationship between the flow stress and the square root of dislocation density in the austenitic phase can be obtained even when martensitic transformation occurs during tensile deformation as well as under the condition of single-phase deformation above the Md temperature. In conclusion, deformation-induced martensites behave not only as hardening bodies by themselves as usually considered, but also as the accelerator of accumulation of dislocations in the austenitic phase. This is because excess dislocations are introduced to accomodate the volume expansion through martensitic transformation and the martensites act as obstacles for slip which results in the increase of dislocation density in the austenitic phase. © 1989, The Japan Institute of Metals. All rights reserved.