Document Type : Original Article
Authors
1
Department of Materials Engineering, Faculty of Engineering, University of Gonabad, Gonabad, Iran
2
Department of Mechanical Engineering, Ilam, Iran
3
Department of Mechanical Engineering, Bu-Ali Sina University, Hamedan, Iran
4
Sama Islamshahr Boys Complex, Islamshahr, Tehran, Iran
Abstract
In this research, copper sheets with different welding conditions, including different rotational and translational speeds of the tool, as well as the number of one and two welding passes, were connected to each other by friction stir welding method. These weldings were performed under helium gas as a protective gas. Blowing helium gas on welds and welding tools prevents air from coming in contact with them and avoids the adverse effects that air can have on them. In this research, due to the softness of the copper metal and the thinness of the sheets, J-integral samples were used instead of the critical stress intensity coefficient KIC samples. This quantity was measured by making C(T) samples. The results of this study showed that due to the occurrence of recrystallization phenomenon in the stirring zone, fracture toughness and Vickers hardness can increase by 41.49% and 52.85%, respectively, compared to the base metal. The occurrence of annealing phenomenon in the heat-affected area leads to the degradation of microstructural and mechanical properties, so that the Vickers hardness, ultimate strength and fracture toughness decrease by 28.57%, 33.90% and 10.98% compared to the base metal, respectively. In addition, the research results showed that in order to obtain a better weld, it is more appropriate to perform the welding process at a lower temperature instead of two or more welding passes, so that less heat is transferred to the workpiece.
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