b'2019 | ANNUAL REPORTFigure 2. Stress vs. weight average lattice strain for unaged, 1000 Developing a mechanistic understanding of mechanicalhours aged and 3000 hours aged response of duplex stainless steel upon long-term reactorspecimens, respectively.service is critical for component life evaluation and reactor license renewal.Results reflections while, for ferrite phase, it Figures 1b and 1c show the engi- was derived from the lattice strains neering strain vs. engineeringof the {110}, {200}, and {211} stress and true strain vs. true stressreflections. The weighted aver-curves, respectively, from the firstaging algorithm was developed by beamline experiment using displace- Daymond [6]. The stress vs. weight ment control mode. It can be seenaverage lattice strain for the first that thermal aging for 1000 hoursexperiments are plotted in Figures greatly changes the mechanical2ac for the conditions of unaged, behavior of the materials, whichaged for 1000 hours, and aged for exhibit increased yield strength but3000 hours, respectively. The yield reduced ductility. To better under- of austenite and ferrite phases were stand the load partition betweenthen determined based on ToMOTAs the austenite and ferrite phasetheory [7]. It clearly showed that the under different aging conditions,yield strength of the ferrite signifi-the weight average lattice strain wascantly increases from 315 up to 437 calculated. The average bulk latticeMPa upon thermal aging for 3000 strain for austenite was derivedhours, while the yield strength of from the lattice strains of the {111},austenite remains nearly unchanged {200}, {220}, {311}, and {420}at around 210 MPa.49'