Induced Martensitic Transformation Effect on Residual Stress, Fatigue and Magnetic Permeability of Austenitic Stainless Steel

This study aims at showing the influence of transformation-induced plasticity (TRIP) on the residual stresses and magnetic permeability of AISI 304 stainless steels and the resulting effect on its fatigue performance. Samples were pre-strained to different levels of plastic deformation, and characterised through metallography, hardness, tensile testing, X-ray diffraction (XRD) and with the MWM^®-array electromagnetic method. Fatigue tests were then conducted on these samples to obtain the S-N curves for each condition, and the resulting fracture surfaces were analysed using scanning electron microscopy (SEM). Residual stress distributions in martensite and austenite were significantly affected by the transformation, although in different ways, and this is thought to be the reason for the improvement in fatigue performance in samples with higher pre-deformation values. Magnetic permeability measurements corroborated XRD results and proved to be a useful tool for non-destructively determining martensite transformation distributions in manufactured components.

Keywords:
Austenitic steel; residual stresses; fatigue; magnetic permeability