Hot deformation behavior and microstructural evolution of dual phase Ni48.6 Al10.3 Co17 Cr7.5 Fe9 Ti5.8 Ta0.6 Mo0.8 W0.4 high entropy alloy

Abstract

The present study reports the hot deformation behavior, microstructural evolution, and the alloying effects of refractory elements (Ta, Mo, W) in Ni48.6 Al10.3 Co17 Cr7.5 Fe9 Ti5.8 Ta0.6 Mo0.8 W0.4 (at. %) high entropy alloy (HEA). The vacuum arc melted specimens were characterized using a scanning electron microscope, X-ray diffractometer, and Differential scanning calorimetry, which revealed the two-phase structure consisting of γ′ precipitates embedded in the γ matrix. The Energy Dispersive Spectroscopy analysis in a scanning electron microscope revealed that Mo and W partitioned into the dendritic region (KMo = 1.23 and KW = 1.28) while Ta is found to be partitioned in the interdendritic region composed of mostly γ′ precipitates (KTa = 0.67). Further, the specimens were subjected to hot deformation in the 800 °C - 1100 °C temperature range at the strain rate of 0.01s−1. The maximum flow strength was around 278 MPa and 183 MPa at 1050 °C and 1100 °C, respectively. The flow behavior is correlated with the microstructure evolution, which is characterized using electron backscattered diffraction (EBSD). In the cases of hot deformation below 1000 °C, localized plastic flow in the form of shear bands developed in coarse grain microstructure, whereas fine grains evolved due to dynamic recrystallization (DRX) in the sample deformed above 1000 °C. Further, the role of refractory elements in retaining high-temperature flow strength has been discussed.