Inference of grain boundary sliding and co-rotation of α/β phases during superplastic deformation of Zr-2.5%Nb at 700 °C through EBSD measurements

Abstract

Present study explains the micromechanics of superplastic deformation of Zr-2.5 wt.%Nb alloy using EBSD analysis. The alloy when deformed in tension at 700 °C and 10−3 s−1 exhibited superplastic flow with total elongation of 650%. Different samples were deformed to intermediate strain levels for characterizing microstructure evolution and subsequently, establishing the underlying micro-mechanisms. EBSD measurements showed that local misorientations within grains did not develop during the superplastic flow. Texture weakening in α and β-Zr phases was observed and it has been shown that the resultant texture is not due to slip-based deformation. Misorientation angle distribution plots revealed a peak at 45° that corresponded to the interface angle between the Burgers OR related α and β phases. The fraction of these interfaces remained unaffected during the superplastic flow. It is concluded that the superplastic flow in Zr-2.5Nb at 700 °C is accommodated by Rachinger grain boundary sliding and co-rotation of α/β grains.