Zn–0.8Mn alloy for degradable structural applications: Hot compression behaviors, four dynamic recrystallization mechanisms, and better elevated-temperature strength

Abstract

• Hot deformation behavior of Zn-0.8Mn alloy are revealed. • Constitutive equation and processing map of the alloy are established. • Four DRX mechanisms, i.e., DDRX, CDRX, TDRX and PSN, are activated. • The alloy exhibits excellent elevated-temperature strengths. Environmentally degradable Zn-0.8Mn alloy is highly ductile, which lays the foundation for developing high-performance Zn-Mn-based alloys. However, not only constitutive equation of this alloy is unknown, but also its dynamic recrystallization (DRX) behavior is unclear, which makes optimization of hot processing parameters of this alloy almost dependent on trial-and-error. This work aims to tackle these problems. The constitutive equation was deduced to be ε ˙ = 1.38 × 10 12 × [sin h (0.009 σ )] 8 exp(–135150/ RT ). A processing map of the alloy was obtained for the first time, which shows that it has excellent hot formability with narrow instability zones. At a final true strain of 0.8, the volume fraction of DRX grains increased from 37% to 79% with temperature increasing from 150 °C to 350 °C and strain rate decreasing from 10 s –1 to 10 –3 s –1 . Discontinuous DRX (DDRX), continuous DRX (CDRX), twinning-induced DRX (TDRX), and particle stimulated nucleation (PSN) were activated during hot compressions. DDRX was always the main mechanism. TDRX was completely suppressed at 300 °C and above. PSN arose from dispersed MnZn 13 particles. Furthermore, Zn-0.8Mn alloy exhibited elevated-temperature strengths better than pure Zn and Zn-Al-based alloys. At 300 °C and 0.1 s –1 , its peak stress was 1.8 times of pure Zn, owing to MnZn 13 particles of 277 ± 79 nm impeding the motion of grain boundaries and dislocations.