b'2019 | ANNUAL REPORTmar345detectorGuard ionslits chamber tensileDe\x1fning specimenslits(a)concurrent evolution mechanism of theIn this research project, we use high- Figure 1. (a) In-situ tensile testing solute clustering and spinodal decom- energy X-ray techniques, includingwith WAXS, (b) engineering stress position are not clear. This knowledgeX-ray diffraction (XRD), extendedvs. stain curves, and (c) true stress vs. true strain curves. gap has hindered the development ofX-ray absorption fine-structure thermodynamic and kinetic modelingspectroscopy (EXAFS) and in-situ tensile of microstructural evolution. It has alsotesting with wide-angle X-ray scat-been speculated that cracks initiate intering (WAXS) to probe the elemental hardened ferrites and then propagatesegregations, phase precipitations and along the phase boundaries betweenlattice-strain status under tensile load ferrite and austenite. However, theof different phases in selected cast fundamental mechanism of how thestainless steels. The studies are comple-microstructural changes decrease themented by advanced microstructural materials fracture toughness has yet tocharacterizations and conventional be determined. This determination istensile testing. For the in-situ tensile needed to construct a physical modelexperiments, only the pristine and to predict the mechanical response tothermally aged materials (sub-sized justify reactor lifetime extension.tensile specimens) were used due to 47'