Dynamic Recrystallization Behavior of Cu-Cr-Nb-Zr Alloy

The dynamic crystallization behavior of the Cu-Cr-Nb-Zr alloy, produced through ingot metallurgy, was meticulously examined using hot compression tests across a temperature range of 850-950 degrees C and a strain rate range of 0.001-1 s-1. Optical microscopy and electron back-scattered diffraction (EBSD) were employed for comprehensive microstructural analysis. The critical conditions dictating dynamic recrystallization (DRX) were ascertained through the strain hardening rate (theta). The initiation of DRX was delineated by determining critical strain and stress, employing theta-sigma and ln theta-epsilon plots. Notably, both critical strain and critical stress exhibited a decreasing trend with increasing deformation temperature. The ratios of critical stress to peak stress and critical strain to peak strain were determined to be 0.90 and 0.57, respectively. The microstructure resulting from DRX exhibited a clear dependence on both the deformation temperature and strain rate. At 850 degrees C, partial DRX led to a heterogeneous microstructure characterized by a combination of large deformed grains with serrated boundaries and fine DRX grains. The recrystallized fraction (XDRX) for the specimens deformed at 850 degrees C displayed an increase with the strain rate, rising from 0.12 at 0.001 s-1 to 0.35 at 1 s-1. In contrast, the specimens deformed at 900 and 950 degrees C revealed fully developed DRX grains. The DRX grain size exhibited a decrease with increasing strain rate for a deformation strain of 0.7. A power-law relation was successfully formulated between the DRX grain size and the Zener-Holloman parameter (Z), demonstrating a good correlation coefficient. This study not only sheds light on the intricate processes involved in dynamic recrystallization but also provides a quantitative relationship between the DRX grain size and the Zener-Holloman parameter for the Cu-Cr-Nb-Zr alloy.