Regulating thermomechanical behavior of W and γ phases in tungsten heavy alloys via Mn-induced strengthening

Abstract

The synergistic deformation behavior between the W and γ phases plays a critical role in governing the microstructural evolution and strengthening mechanisms of tungsten heavy alloys (WHAs). Here, we systematically investigate the thermomechanical behavior and constitutive models of W-NiFeCo and W-NiFeCoMn alloys, with emphasis on the distinct deformation roles of each phase and the strengthening effect of Mn element. Four constitutive models were established, among which the modified Johnson-Cook equation exhibited the highest predictive accuracy over a wide deformation range (600–1200 °C, 10⁻³–1 s⁻¹). Deformation temperature plays a dominant role in determining hot workability. Below the recrystallization temperature of the γ phase, stress-induced specific orientation relationships between W and γ phases promote coordinated deformation and efficient strain hardening. However, excessive deformation temperatures promote γ phase recrystallization and W grain coarsening lead to the mixed grain in WHAs, degrading interphase compatibility and increasing instability risk. Mn addition significantly raises the γ phase recrystallization temperature, suppresses mixed grain formation, and enables stable softening of W particles under high temperatures. Additionally, solid-solution strengthening by Mn enhances γ phase strength and reduces the mechanical mismatch between phases, thereby improving co-deformation and work-hardening. Processing maps indicate that, for the W-NiFeCoMn alloy, deformation at 800 °C and a strain rate of 0.005 s⁻¹ corresponds to a high-power dissipation efficiency and stable flow behavior, whereas the W-NiFeCo alloy exhibits a greater tendency toward early γ phase recrystallization and local flow instability under comparable conditions.