The dependence of Zener-Hollomon parameter on softening behavior and dynamic recrystallization mechanism of a biodegradable Zn-Cu-Mg alloy

•The Zn-Cu-Mg alloy exhibits excellent heat resistance.•The mechanisms of TDRX/CDRX/DDRX and their corresponding effects on the nucleation of new orientations and texture evolution are thoroughly studied.•The promotion of DRX and the enhancement of strain hardening rate can be achieved by increasing the strain rate at high lnZ.•The deformation processing at high lnZ is feasible, which is significant for understanding the hot workability of degradable Zn alloy due to its high efficiency and low cost. The Zn-Cu-Mg alloy exhibits good strength, ductility, anti-aging and antibacterial properties, which lays the foundation for developing high performance Zn-based biodegradable alloys. However, the constitutive equation and dynamic recrystallization (DRX) behavior of this alloy remain unclear, making the optimization of hot processing parameters almost dependent on trial and error. This work aims to address these issues by investigating the hot compression process. The calculated average activation energy Q of this alloy is 141.338 KJ⋅mol-1, exhibiting excellent heat resistance. The deformed microstructure strongly depends on the Zener-Hollomon parameter (Z=ε˙exp(QRT)). Discontinuous DRX (DDRX) dominates at low lnZ, which has a significantly different orientation from the parent grain. Continuous DRX (CDRX) occurs within the grain and at grain boundaries, and is dominant at middle lnZ, mainly through activation 〈a〉 or/and 〈c+a〉 slip systems. Additionally, the activation of prismatic slip further promote CDRX, and most CDRX grains inherit the 30°[0001] orientation from the parent grains. The volume fraction of DRX demonstrates a decreasing trend followed by an increasing trend with increasing lnZ. At high lnZ, the increase of DRX grains is conducive to weakening the texture, and twin-induced DRX (TDRX) is significantly promoted, leading to an increase in both peak stress and strain hardening rate. Furthermore, the grains with c-axis aligned parallel to the compression direction (CD) are more prone to twinning, while the c-axis perpendicular to CD are the hard orientation of basal slip and compression twins. TEM results reveal that a decrease of c/a value promotes the activation of non-basal slip near the twin boundary, and the highly active 〈c〉 and 〈c+a〉 slips contribute to the increase of strain hardening rate. The results of this study are significant for understanding the workability of Zn-Cu-Mg alloys at high lnZ due to its high efficiency and low cost.