Microstructure evolution of FeNiCr alloy induced by stress-oxidation coupling using high temperature nanoindentation

The microstructure evolution of a FeNiCr alloy oxidized at 600 °C by simultaneously applying stress via high temperature nanoindentation is reported. Analysis using transmission electron microscopy shows that a sharp crack was induced beneath the indentation area under the stress-oxidation coupling condition. Nanotwins beneath the indentation area were also observed, which acted as a barrier that ceased the crack propagation beneath the indenter by altering the path of the crack. Results reveal a transformation from inter-granular crack propagation along the oxide grain boundaries to intra-granular crack propagation through the nanotwin structure with a zig-zag pattern.