Prediction of grain size and mechanical properties in friction stir welded pure copper joints using a thermal model

In this study, a thermal model was developed and applied to simulate the friction stir welding of pure copper plates with the thickness of 2 mm. The different traverse speeds of 100, 200, 300, and 400 mm min(-1) and rotational speeds of 400, 700, 900 rev min(-1) were considered as welding parameters. Microstructural characterization, hardness measurement, tensile test, and fractography were conducted experimentally. The comparison between the numerical and experimental results showed that the developed model was practically accurate. In addition, the results confirmed that the peak temperature was the dominant factor controlling the grain size and mechanical properties, where the fine grains could be achieved at low rotational speed as well as high traverse speed. Consequently, lower peak temperature leads to the high ultimate tensile strength and hardness and the low elongation values.