In situ neutron diffraction study on temperature dependent deformation mechanisms of ultrafine grained austenitic Fe–14Cr–16Ni alloy

Abstract

Using in situ neutron diffraction technique we investigated the temperature dependent deformation mechanisms in ultrafine grained (UFG) austenitic Fe–14Cr–16Ni alloy prepared by equal channel angular pressing. Tensile test studies show diminished ductility when testing temperature increased from 20 to 200°C. At 200°C, non-linear lattice strain deviation on [200] orientation proceeded plastic yielding by a large margin, accompanied by a greater distortion of crystal structure. In addition, the capability to accumulate dislocations was substantially reduced at 200°C as evidenced by lower dislocation density than that at 20°C. Dynamic recovery expedited at elevated temperature because of enlarged critical separation distance for annihilation of dislocation dipoles via climb. Calculations show that both high angle grain boundaries and thermal kinetic energy assisted the reduction of vacancy formation energy.