Aluminium and copper plates with 3 mm thickness were successfully friction stir lap welded at a lower rotation rate of 600 rev min 21 using a larger pin 8 mm in diameter. Good metallurgical bonding on the Al/Cu interface was achieved due to the formation of a thin, continuous and uniform Al-Cu intermetallic compound layer. Furthermore, many Cu particles consisting of pure Cu and intermetallic compound layers were generated at the lower part of the nugget zone, forming a composite structure with increased hardness. A lower rotation rate resulted in a decrease in annealing softening in the heat affected zone (HAZ), and a larger diameter pin increased the Al-Cu bonding area. These factors resulted in that the friction stir welded lap joint exhibited a high failure load of 2680 N with failure in the HAZ on the aluminium side.

Objective To investigate the feasibility of focused ultrasound therapy for recurrent cervicitis with high-risk human papillomavirus (HR-HPV) infection. Methods

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The influence of different lap configurations and preheating process on the macro-/microstructures and mechanical properties of friction stir spot welding welds with both similar and dissimilar materials (6061-T6 aluminium alloy and AZ31B magnesium alloy) was investigated. The results showed that the different lap configurations resulted in different macro-/microstructures and mechanical properties of welds. Defect free welds and intermetallic compound containing welds were obtained in configurations of similar (Mg/Mg and Al/Al) and dissimilar (Mg/Al and Al/ Mg) respectively. The welds with similar materials had the highest tensile shear strengths, followed by the Mg/Al welds; the Al/Mg welds had the lowest strength. The preheating process improved the tensile shear strengths of Mg/Mg, Al/Al and Mg/Al welds and reduced that of Al/Mg welds respectively.