Dynamic recrystallization mechanisms operating in a Ni–20%Cr alloy under hot-to-warm working

The structural mechanisms responsible for the development of new grains in a Ni–20%Cr alloy during hot-to-warm working were studied in compression at temperatures of 500–950 °C. A bilinear relationship between the flow stresses and the dynamic grain sizes was obtained with an inflection point at 7 × 10−3G. The dynamic grain size can be related to the flow stress through power-law functions with grain size exponents of −0.7 and −0.25 for low and high flow stresses, respectively. The variation of the stress versus grain size dependence is attributed to the change in mechanisms of new grain development from discontinuous to continuous reactions with increasing flow stress. The former is associated with the grain boundary bulging and the latter is related to a strain-induced phenomenon involving the development of large angular misorientations between deformation subgrains after large strains.