MICROSTRUCTURE EVOLUTION OF TWO KINDS OF HIGH-TEMPERATURE RESISTANCE FE-CR-NI ALLOYS Pan, Weiqi Materials Science Cr23C6/Cr7C3 G-phase Heat resistance alloys NbC phase Phase evolution In this research, two different as-cast Fe-Cr-Ni alloys (35Cr-45Ni, 25Cr-35Ni) were aged at different times (1h, 10h, 100h, 1000h) and temperature (700℃, 800℃, 900℃, 1000℃). These different aged alloys were studied by optical microscope, scanning electron microscope (SEM), Energy-dispersive spectroscopy (EDS), X-ray diffractometer, micro Vickers hardness tester. The aged sample showed a higher hardness than the as-cast one. The hardness also changed as time and temperature increased because diffusion result on phase transformation and precipitation. Both as-cast 35Cr-45Ni and 25Cr-35Ni have MC (NbC) and M7C3 (Cr7C3) phase transformation during aging. The long term high-temperature aging caused changes carbides and silicide phase. For both alloys during aging, MC carbides transformed to G-phase, and Cr7C3 transformed to Cr23C6. Tin, Sammy 2019 Thesis application/pdf islandora:1000850 http://hdl.handle.net/10560/islandora:1000850 Illinois Institute of Technology MMAE / Mechanical, Materials, and Aerospace Engineering en In Copyright http://rightsstatements.org/page/InC/1.0/ Restricted Access