High-Resolution Neutron Diffraction Analysis of Residual Stresses in Oxide Dispersion Strengthened FeNiCrY2O3 Cast Alloys for Advanced Nuclear Reactor Applications

High-temperature resistant materials have been developed, including Fe-base austenitic steel with high Ni-Cr content. These materials are modified into oxide dispersion strengthened (ODS) steel incorporated with a small amount of rare earth element (REE) oxides. ODS alloys are a mixture of a metal matrix with uniformly distributed small oxide particles. The alloys show great promise as structural materials for modern engineering applications in advanced- energy and nuclear reactors. A comprehensive understanding of individual mechanical properties and residual stress distribution remains elusive. Therefore, this research aimed to show the influence of Y2O3 dispersion on the crystal structure and residual stress in FeNiCr Y2O3 cast alloys with varying ODS compositions ranging from 0 to 2.0 wt.% Y2O3. Alloys were synthesized by powder metallurgy and melt casting followed by characterization using neutron diffraction as well as standard metallographic methods. During analysis, neutron was powerful for probing solid materials, among other things. The product penetrated deep inside, which made it possible to research bulk properties and internal structures of thick samples or materials encased in containers. Diffraction profile analysis showed that cast alloys signified 'matrix-cluster' composite crystal morphology and improved elemental mapping of the microstructure. Moreover, stress-strain curves moderately estimated optimum Y2O3 content to be 1.0 wt.%. Y2O3 dispersion induced lattice compression in the austenitic FeNiCr matrix, signifying tensile residual stress in the crystals. Distribution of residual stress in alloys was related to mechanical and performance properties. In conclusion, most recommended materials for further fabrication as FeNiCr Y2O3 ODS cast alloys was 57Fe25Ni17Cr1.0Y2O3 system.