Paolo Ferro

TL;DR: In this article, a study of three different welded joints produced by electron beam welding dissimilar materials was presented, which showed complex heterogeneous fusion zone microstructures characterized both by rapid cooling and poor mixing of materials which contain main elements which are mutually insoluble.

TL;DR: In this article, the fatigue strength of Ti-6Al-4V blunt V-notched samples produced by the selective laser melting (SLM) process is assessed. But despite the observed fatigue strength reduction induced by the notch, samples showed a sufficient low notch sensitivity that it was not possible to define a critical radius for the material analysed.

TL;DR: In this article, the influence of phase transformation on the residual stress induced by the welding process, by comparing the results obtained with the described differences in the analyses, was examined, and it was found that both volume changes due to phase transformations and transformation plasticity have a great influence on the in-plane stresses induced by welding process.

TL;DR: In this article, a finite element model of the process has been set up using an uncoupled thermal-mechanical analysis, and the predicted residual stresses were then compared with X-ray diffraction measurements.

Abstract: CO 2 laser welding was performed on AISI 904L superaustenitic stainless steel sheets, with optimised processing parameters determined by means of melt run trial evaluations. X-ray diffraction phase identification and light microscopy confirmed that the weld structure is fully austenitic and dendritic. A hardness increase in the weld bead with respect to the parent metal occurred and was related to both the microstructural refinement induced by a rapid cooling of the fusion zone and the presence of nanometric scale precipitates observed by TEM in the weld bead. Residual stresses were determined by means of X-ray diffraction, exhibiting tensile stresses, close to the yield strength, in the longitudinal direction in the weld bead, while the stresses were compressive in the transverse direction and in the base material. Tensile tests showed that welded specimens retained strength and ductility values comparable to those of the base material.