Description of Grain Refinement by Dynamic Recrystallization Under Hot Compressions for As-Extruded 3Cr20Ni10W2 Heat-Resistant Alloy

Abstract

Abstract The dynamic recrystallization (DRX) behavior of as-extruded 3Cr20Ni10W2 heat-resistant alloy was investigated by hot compressions with a fixed height reduction of 60% over a temperature range from 1,203 to 1,403 K and a strain rate range from 0.01 to 10 s−1. Results show that DRX occurs more easily at lower temperatures and higher strain rates, the stress level increases significantly with the increase of deformation temperature or the decrease of strain rate. Under such wide range of deformation conditions the flow stress evolution generally indicates two characteristics: work hardening (WH) followed by DRX, or by dynamic recovery (DRV). The variation of the average size of grains refined by DRX behavior in the alloy is characterized by linking the deformation conditions during hot compression process. At a fixed temperature, the average grain size linearly decreases with increasing strain rate in log scale. At a lower strain rate, the average grain size rapidly increases with increasing temperature, while it remains almost constant at strain rate of 10 s−1. At a higher strain rate, grain size data sets tend to be closer to the average size value, which indicates that as strain rate increases, the microstructures become more and more uniform. The effects of the temperatures and strain rates on the average grain size can be represented by Zener–Hollomon parameter, Z, and the relationships between the average grain size and Z parameter can be described as a nonlinear equation, which indicates that the average grain size decreases with increasing Z parameter. On the plot of average grain size D A $${D_A}$$ – l n Z $${\rm{ln}}\,Z$$ , the regions corresponding to DRV ( l n Z ≤ 77.9 $${\rm{ln}}\ Z\,\le \,77.9$$ ) and DRX ( l n Z > 77.9 $${\rm{ln}}\ Z\,\gt \,77.9$$ ) were clarified clearly.