TENSILE BEHAVIOR OF A NEW SINGLE-CRYSTAL NICKEL-BASED SUPERALLOY (CMSX-4) AT ROOM AND ELEVATED-TEMPERATURES

Tensile behavior of a new single-crystal nickel-based superalloy with rhenium (CMSX-4) was studied at both room and elevated temperatures. T he investigation also examined the influence of gamma' precipitates (s ize and distribution) on the tensile behavior of the material. Tensile specimens were prepared from single-crystal CMSX-4 in [001] orientati on. The test specimens had the [001] growth direction parallel to the loading axis in tension. These specimens were given three different he at treatments to produce three different gamma' precipitate sizes and distributions. Tensile testing was carried out at both room and elevat ed temperatures. The results of the present investigation indicate tha t yield strength and ultimate tensile strength of this material initia lly increases with temperature, reaches a peak at around 800-degrees-C , and then starts rapidly decreasing with rise in temperature. Both yi eld and tensile strength increased with increase in average gamma' pre cipitate size. Yield strength and temperature correlated very well by an Arrhenius type of relationship. Rate-controlling process for yieldi ng at very high temperature (T greater-than-or-equal-to 800-degrees-C) was found to be the dislocation climb for all three differently heat- treated materials. Thermally activated hardening occurs below 800-degr ees-C whereas above 800-degrees-C thermally activated softening occurs in this material.