Sorensen, Daniel David2014-10-152014-10-152014-08https://hdl.handle.net/11299/166866University of Minnesota Master of Science thesis. August 2014. Major: Material Science and Engineering. Advisors: William W. Gerberich, K. Andre Mkhoyan. 1 computer file (PDF); vii, 81 pages.The mechanism of secondary hardening in MP35N (Co-35Ni-20Cr-10Mo) alloy due to exposures at elevated temperatures has been studied. It was observed that short exposure to elevated temperatures increased the ultimate tensile strength and yield stress while decreasing the elongation of MP35N wires. Upon aging at temperatures from 300 to 900°C the elastic modulus increased although no changes in crystallographic orientation or microstructure were observed. No proposed model for this apparent increase in elastic modulus is suggested as yet. The grain size and major texture components were unchanged following aging. Analytical scanning transmission electron microscope investigation showed that MP35N is hardened by preferential segregation of molybdenum to stacking faults and deformation twins. It also revealed that the concentration of molybdenum segregation was proportional to the amount of initial cold work before aging.enAgingEDSEELSMP35NSecondary hardeningSTEMMaterial science and engineeringThesis or Dissertation