In Situ Stress Measurements by Neutron Diffraction in α-γ Fe-Cr-Ni Alloys During Deformation

Abstract

In situ neutron diffraction experiments during tension-compression deformation were performed for five Fe-Cr-Ni alloys with the volume fraction of ferrite varied from 0.0 to 100 %. Specimens were strained by tensile deformation with a step by step manner up to a few percent plastic strain followed by unloading and then subsequently deformed in compression in the same manner. The lattice plane spacings of ferrite (α) and austenite (γ) single-phase alloy before loading were used as reference stress-free spacings to determine lattice strains in the α-γ dual phase alloys. It has been found that the large residual lattice strains generated by tensile deformation cause a large Bauschinger effect in the α-γ dual phase alloy. Due to high resolution of the used neutron diffractometer, microstrains in both phases could be extracted from diffraction profiles. The obtained microstrains do not vary during elastic deformation while a significant increase with an increase of plastic strain was observed.