Effect of precipitation on the mechanical and damping properties of (FeCrCoNi)95Ti5 high-entropy alloy

Abstract

The microstructure, mechanical properties, and damping properties of a (FeCrCoNi)₉₅Ti₅ high-entropy alloy after a series of aging treatments were studied. The alloy had a face-centered cubic (FCC) structure, and its microstructure was characterized by typically equiaxed grains. The effects of the γ′ precipitates and lamellar η on the mechanical and damping properties of the alloy were studied. In addition, the mechanisms of strengthening and deformation were explored. Owing to the precipitation strengthening of the γ′ precipitates, the yield strength of the alloy after aging at 873 K was 513 MPa, which was 52 % higher than that before the treatment (337 MPa). Meanwhile, the elongation was 53 %; only a 5 % reduction in elongation was achieved. After aging at 973K and 1073K, the lamellar η phase significantly increases the yield strength of the alloy to 755 MPa and 818 MPa, but the elongation decreases to 36 % and 25 %, respectively. After the deformation, a large number of dislocations piled up in the η phase and formed high-density dislocation walls. In the γ′ phase, a large number of cross-stacking faults were generated, which formed Lomer–Cottrell locks. With an increase in the aging temperature, the microstructure changed, and the deformation mechanism began to change from the stacking-fault control mode to the dislocation-stacking fault co-dominant mode. The damping mechanism of the alloy satisfied the G-L dislocation model, and the damping parameter $Q^{-1}$ of the solid solution alloy was approximately 0.035. Following aging at 873 K, the γ′ precipitates acted as weak pinning points in the alloy. When the dislocation approached the interface, it continued to pass through the interface and consumed energy, which further improved the damping capacity of the alloy. The $Q^{-1}$ value reached approximately 0.045, and the η precipitation of the phase reduced the value further. The $Q^{-1}$ values of the alloys aging at 973 K and 1073 K were 0.038 and 0.036, respectively.