Issue 47

P. Ferro et al., Frattura ed Integrità Strutturale, 47 (2019) 221-230; DOI: 10.3221/IGF-ESIS.47.17 226 Figure 6 : SEM micrograph of the HAZ before (a) and after (b) TIG-dressing. Figure 7 : Microhardness profile across the weld bead. Fig. 8 shows the temperature distribution at the point when the fusion zone has its maximum width (the fusion zone is shown in red). It also shows, as comparison, the macrograph of the joint cross section before and after TIG-dressing. It has to be underlined that the heat source and welding parameters are estimated by the comparison between the predicted and real fusion zone shape and dimensions and a sound agreement is obtained (Fig. 8). The proportional distributions of phases after cooling with a comparison with experimental results are shown in Fig. 9. According to numerical simulation, each FZ is characterised by ferrite. However, it is worth noting that the model does not distinguish its different morphologies shown in metallurgical analysis (allotriomorphic, acicular and Widmanstatten ferrite). The heat-affected zone (HAZ) is instead characterized by a balanced amount of bainite and tempered bainite. SEM micrograph (Fig. 9) and micro-hardness measurements (Fig. 7) confirm the obtained numerical results.