Misfit in Inconel-Type Superalloy

[摘要] An important parameter for the characterization of microstructural changes in nickel base superalloys is the misfit - the relative difference between lattice parameters ofγmatrix andγ′precipitates. The misfit in IN738LC superalloy was examined at POLDI time-of-flight (TOF) neutron diffractometer both at room temperature and in situ at elevated temperatures using a high-temperature furnace. A careful out-of-furnace measurement yielded the lattice parameters of bothγandγ′phase at room temperature (aγ=3.58611(10) Å,aγ′=3.58857(17) Å) as well as the misfit (equal to6.9(6)×10-4). The in situ measurement at elevated temperatures provided the temperature dependence of the lattice parameters ofγ(up to 1120°C) andγ′(up to 1000°C). Using these data, the evolution of the misfit with temperature was calculated. The misfit decreases with increasing temperature until it reaches zero value at a temperature around 800°C. Above 800°C, it becomes negative.

[学科分类] 材料工程