Abstract
This thesis presents work performed to develop the understanding of microstructural evolution and the deformation micromechanisms that occur in nickel based and refractory superalloys, a newer class of high temperature materials.
A thorough understanding regarding microstructure-mechanical property relationships of high temperature superalloys remains challenging, as the microstructure is temperature, stress and time dependent and multiple strengthening mechanisms contribute to strength. In-situ x-ray and neutron diffraction can offer unparalleled insight regarding phase evolution and deformation micromechanisms at the temperatures and stresses of importance to gas-turbine applications, however diffraction analysis have not been applied to the study of multimodal gamma prime distributions in nickel based superalloys and multi-phase refractory superalloys. The diffraction analysis presented herein demonstrates the capability to determine critical microstructural parameters in-situ within these materials and is an additional tool to understanding microstructure-mechanical property relationships of high temperature structural materials. The use of in-situ diffraction in conjunction with electron microscopy analysis gives significant insight into the deformation micromechanisms of complex alloy systems that would be extremely difficult to garner from traditional post-mortem material characterization techniques since the characterization conditions of conventional electron microscopy and mechanical testing may not be representative of the microstructure and deformation micromechanisms under the temperature and stresses of relevance.