THE EFFECT OF GAMMA PRIME PARTICLE SIZE UPON THE HIGH TEMPERATURE PROPERTIES OF NICKEL-BASE ALLOYS

The principal conclusions as a result of the investigation, regarding gamma prime-containing NiCr-Al alloys indicate that 1 as the Al content increases, faster cooling rates from above the solution temperature are required to develop maximum room temperature hardness 2 room temperature hardness, as well as tensile strength and creep strength at elevated temperatures, increase initially with increasing Al 3 an exhaustion effect is noted, by which the room temperature hardness of high-Al compositions is less sensitive to changes in aging temperature than that of low-Al compositions 4 very large particle sizes can be readily developed by slow cooling from above the solution temperature and 5 an optimum-mean-free-path between gamma prime particles exists, which results in minimum creep rate. This optimum-mean-free-path along with the corresponding particle size for a given volume percent of gamma prime varies with applied stress. Manganese and titanium expand the lattice of the gamma matrix, and manganese reduces the quantity of gamma prime precipitate. Author