Tensile behavior of a new single-crystal nickel-based superalloy (CMSX-4) at room and elevated temperatures

Abstract

Tensile behavior of a new single-crystal nickel-based superalloy with rhenium (CMSX-4) was studied at both room and elevated temperatures. The investigation also examined the influence of γ′ precipitates (size and distribution) on the tensile behavior of the material. Tensile specimens were prepared from single-crystal CMSX-4 in [001] orientation. The test specimens had the [001] growth direction parallel to the loading axis in tension. These specimens were given three different heat treatments to produce three different γ′ precipitate sizes and distributions. Tensile testing was carried out at both room and elevated temperatures. The results of the present investigation indicate that yield strength and ultimate tensile strength of this material initially increases with temperature, reaches a peak at around 800 °C, and then starts rapidly decreasing with rise in temperature. Both yield and tensile strength increased with increase in average γ′ precipitate size. Yield strength and temperature correlated very well by an Arrhenius type of relationship. Rate-controlling process for yielding at very high temperature (T ≥ 800 °C) was found to be the dislocation climb for all three differently heat-treated materials. Thermally activated hardening occurs below 800 °C whereas above 800 °C thermally activated softening occurs in this material.