In situ analysis of the Portevin-Le Chatelier effect from low to high-entropy alloy in equal HfNbTaTiZr system

Abstract

The HfNbTaTiZr system is designed from low-entropy to high-entropy by unary, binary, ternary, quaternary, and quinary equal-molar element alloys. At first, the effect of mixing entropy on elevated temperature tensile behaviors ranging from 400 °C to 800 °C and strain rate 1 × 10−4 s–1 in body-centered-cubic (BCC) alloys is systematically discussed, including dynamic strain aging, serration behavior and in-situ deformation behavior of Portevin-Le Chatelier (PLC) band analysis. The results show that in BCC high-entropy alloys (HEAs), with the increase of the alloy elements, the range of the transition temperature of PLC bands expands, and the degree of dynamic strain aging at high temperature also enhances. The theoretical model was verified with the critical strain of unary, binary, and ternary alloys, and it predicts the PLC effect under the specific temperature and strain rate. Apply Applied to quinary alloys, the difference in serration phenomena between face-centered-cubic (FCC) and BCC HEA are investigated, showing that the high melting point of Nb and Ta elements lead to the slower self-adjusting velocity in HfNbTaTiZr alloy. Digital image correlation analysis is in-situ to analyze different types of PLC bands at various strain rates from 1 × 10–2 to 1 × 10−3 s–1 and elevated temperature from 200 °C to 600 °C. The BCC single-phase HEA reveals the transmission properties of the PLC bands and it is consistent with the serration behavior in the tensile stress-strain curve.