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. transformationinduced induced TRIP (TRIP 30 prestrained pre strained deformation metallography hardness testing Xray X ray (XRD MWM®array MWMarray MWM® array MWM method SN S N condition SEM. SEM . (SEM) ways predeformation values nondestructively non destructively components 3 (SEM

Continuous cooling bainitic steels has been widely used in industrial processes owing to its excellent mechanical properties and toughness. Although the surface properties of them are acceptable for many purposes, for their use in mechanical components like gears, it is necessary to improve their surface properties. Plasma nitriding treatments was carried out of a DIN 18MnCrSiMo6-4 steel at 500 °C, with three different nitrogen gas composition: 76, 24 and 5 vol.% nitrogen in hydrogen, for 3, 6 and 9 hours. The surfaces were characterized concerning the microstructure, microhardness, fracture toughness, nitrogen concentration and carbon composition, phase composition and residual stress states. Based on the results presented, layer growth constants (k) for different nitrogen gas composition was determined. The carbon profiles of samples indicate that there was decarburization during the plasma nitriding. The nitrided samples with thicker compound layers presented a fracture behavior dominated by the formation of Palmqvist cracks. X-ray phase analysis indicated the formation of biphasic compound layer on the surface of all nitrided samples with 76 and 24 vol.% nitrogen, while the nitrided samples with 5 vol.% nitrogen indicated the formation of monophasic compound layer. The diffusion zone presented compressive residual stresses with highest values near the surface.

This paper aims at analyzing the effects of the roller pre-straightening of wire-rods on residual stress distributions in SAE 1045 steel bars. The combined drawing process is used in industrial production of bars in order to obtain a good surface quality and improved mechanical properties complying with specifications of the final products. In this process, prior to the drawing step, a roller straightening of the steel wire-rod is essential, because it provides the minimum straightness necessary for drawing. Metallographic analysis and hardness test were done for selected samples after different processing steps. Also, residual stress analysis of pre-straightened wire-rods by X-ray diffraction and neutron diffraction were carried out. The hardness tests show higher values near the surface and lower in the center of the wire-rod. Besides, the residual stresses results show a big inhomogeneity from one peripheral position to another and also in the evaluated cross section.