|About this Abstract
||Materials Science & Technology 2019
||Materials for Nuclear Applications
||Evolution of Microstructure, Deformation Mechanisms, and Internal Damage During Creep-Fatigue Testing of Alloy 709 (Fe-20Cr-25Ni)
||Ty Porter, Kip Findley, Michael Kaufman, Richard Wright
|On-Site Speaker (Planned)
Alloy 709, a precipitation and solution strengthened 20Cr-25Ni-1.5Mo-Nb-N austenitic stainless steel, is a candidate alloy for structural components in sodium cooled fast nuclear reactors, where creep-fatigue performance is critical. Strain controlled low cycle fatigue (LCF) and creep-fatigue tests with 1 pct total strain were performed from 500-700 °C, with tensile hold times of 0-30 mins, and with different initial microstructures to investigate the influence of microstructural evolution on deformation and damage mechanisms. Under conditions where dynamic precipitation is significant, a transition in slip behavior from planar to wavy leads to dynamic recovery at grain boundaries and a significant reduction of intergranular crack propagation as plastic deformation is enhanced at crack tips. Easier cross-slip is attributed to a consumption of solute atoms during dynamic precipitation of carbides and nitrides. Pre-aging the alloy to a near-equilibrium precipitate volume fraction leads to a three-fold increase in creep-fatigue life at the expected service temperature.
||Definite: At-meeting proceedings