Effect of short-range order on the high-temperature plastic deformation behavior of Ni–Cr–W, Ni–W, and Ni–Re single crystals

Abstract

The development of a Ni-based superalloy that consists of only the γ-solid-solution phase is highly desired for some applications such as high-temperature gas-cooled reactors in power plants. In this study, the temperature dependence of the plastic deformation behavior of Ni–22Cr–8W (at%) alloy was examined for the first time by using a single crystal, focusing on the influence of the short-range order (SRO), especially upon high-temperature deformation behavior. The critical resolved shear stress (CRSS) for (111)[101¯] slip exhibited a rapid decrease as the temperature increased at low temperatures but an almost constant value of ∼45 MPa between 500 and 900 °C. In addition, a slight yield stress anomaly (YSA) was observed, reaching a maximum value at 1000 °C.To clarify the influence of the SRO on the YSA behavior, the mechanical properties of Ni–8W and Ni–5Re single crystals were also examined. Similar temperature dependence for the CRSS, including the occurrence of slight YSA, was observed for Ni–8W, in which SRO developed. In the Ni–5Re single crystal in which SRO did not significantly develop, however, the CRSS monotonically decreased as the temperature increased. The results suggest that the presence of SRO in a Ni–Cr–W alloy contributes to the strengthening of the alloy not only at low temperatures but also at high temperatures up to ∼1000 °C. The results strongly suggested that the pseudo-PLC effect is related to the origin of YSA appearing in Ni-based γ-solid-solution alloys at high temperatures.