Microstructure and mechanical property of friction plug welded joint for H62 brass alloy
Aiming to address welding defects in copper and copper alloys,an effective method is proposed for in-situ repair of copper components using friction plug welding to achieve keyhole and defect filler welding.A top forging type friction plug welding machine is used to weld H62 brass alloy in this study,the temperature profile,microstructure and mechanical properties of H62 brass friction plug joints are analyzed by temperature measurements,optical microscope,scanning electron microscope,tensile testing and hardness testing.The differences in the properties of the joint under four different spindle speeds were studied.The results show that the upper layer of the joint plug exhibits a fine recrystallization microstructure,while the lower layer consists of a mixed structure of columnar grains and crystallized grains.The hardness distribution of the joints shows a"W"-shaped,with the highest hardness at the center of the plug bar and the lowest hardness at the friction interface.The peak temperature of the joint increases with the spindle speed,while the temperature differene between the upper,middle and lower layers gradually decreases.The grain size of the upper layer at the friction interface of the joint is the smallest at the same spindle speed,and the grain size gradually increases downward along the thickness direction.The peak temperature is the highest in the upper layer of the joint,followed by the middle layer,and lowest in the lower layer.At a spindle speed of 2 200 r/min,the joint exhibits the best overall mechanical performance.The tensile strength of the joint is 350.5 MPa,which is equal to 358.4 MPa of the base material.The fracture mode of the joint is ductile fracture.In addition,the upper layer of the plug bar fracture is the smallest and densest under the temperature gradient and mechanical action,showing the best mechanical properties,while the lower layer fracture shows poorer plasticity performance.
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