Microstructural analysis by scanning thermal microscopy of a nanocrystalline Fe surface induced by ultrasonic shot peening

Experiments were carried out using a scanning thermal microscope (SThM) to investigate the ultrafine-grained microstructures in the surface layer of a pure iron sample produced by ultrasonic shot peening. The analysis of thermal properties by SThM shows that the thermal conductivity strongly depends on the grain size of the microstructure. The different contrasts on the thermal conductivity images are used to estimate the thickness of the affected surface layer produced by ultrasonic shot peening. The results demonstrate that the SThM can be used as a powerful tool for the microstructural analysis of the ultrafine-grained surface layer.