Showing papers by "Hiroyuki Kokawa published in 2016"
TL;DR: The welds with weld energies of more than 1.05 kJ fracture in the base metal and were severely deformed by the ultrasonic vibration, and recrystallization occurred around the weld interface owing to the shear deformation and heating during ultrasonic welding as discussed by the authors.
87 citations
TL;DR: In this paper, the microstructural changes occurring during cooling of friction-stir welded aluminum alloy AA1100 were evaluated and electron backscatter diffraction was used to study the evolved microstructures.
Abstract: In this work, the microstructural changes occurring during cooling of friction-stir welded aluminum alloy AA1100 were evaluated. To this end, friction-stir welding (FSW) was performed in a wide range of cooling rates of 20–62 K/s and the evolved microstructures were studied by using electron backscatter diffraction. Below 0.6 Tm (Tm being the melting point), the stir zone material was found to experience no significant changes during cooling. At higher FSW temperatures, however, notable changes occurred in the welded material, including grain growth, sharpening of texture, reduction of the fraction of high-angle boundaries and material softening.
14 citations
TL;DR: In this paper, the effect of the heat input on the grain size of the stir zone was examined, and a good correlation between the grain sizes and heat input was obtained, which is a basic index for weld quality and service properties associated with the resulting microstructure.
Abstract: Heat input during welding is a basic index for weld quality and service properties associated with the resulting microstructure. In this study, the heat inputs during friction stir welding of Al alloy 5083 at various welding parameters were measured by calorimetry. Multiple regression analysis of the data was conducted to determine an empirical equation to estimate the heat input with the input variables. The effect of the heat input on the grain size of the stir zone was also examined, and a good correlation between the grain size and heat input was obtained. This study obtained a systematic relationship between the input variables, heat input and grain size of the stir zone through experimental measurements.
12 citations