Grain growth and Hall-Petch relationship in a refractory HfNbTaZrTi high-entropy alloy

By Shuying Chen, K. Tseng, Yang Tong, Weidong Li, Che-Wei Tsai, Jien‐Wei Yeh, P. K. Liaw. Journal of Alloys and Compounds, 2019

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Abstract Understanding the effect of temperature variation on the microstructural evolution is particularly important to refractory high-entropy alloys (RHEAs), given their potential high-temperature applications. Here, we experimentally investigated the grain-growth behavior of the HfNbTaZrTi RHEAs during recrystallization at temperatures from 1,000 to 1,200 °C for varied durations, following cold rolling with a 70% thickness reduction. Following the classical grain-growth kinetics analysis, two activation energies are obtained: 205 kJ/mol between 1,000 and 1,100 °C, and 401 kJ/mol between 1,100 and 1,200 °C, which suggests two mechanisms of grain growth. Moreover, the yield strength – grain size relation was found to be well described by the Hall-Petch relation in the form of σ y = 942 + 270 D − 0.5 . It was revealed that the friction stress, 942 MPa, in the HfNbTaZrTi HEA is higher than that of tungsten alloys, which indicates the high intrinsic stress in the BCC-RHEA. The coefficient, 270 MPa/μm −1/2, is much lower than that in the 316 stainless steel and Al0.3CoCrFeNi HEAs, which indicates low grain-boundary strengthening.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/a417903a127a2efbf7568fe5e070fec8cf58b4f7