Mechanical Properties And Joint Formation Mechanism Of Friction Stir Spot Welding

Friction stir welding(FSSW) which is a solid-state welding process based on the Friction weld.Friction stir welding in lightweight aluminum alloy welding has irreplaceable advantages.In recent years, along with aluminum and other light alloys widely used in the automotive industry.Friction stir welding of aluminum welding has very important significance.In this paper,we carry out FSSW of without keyhole welding2mm+2mm thick6082-T6aluminum alloy lap joint and LY12aluminum alloy lap joint and analysis the mechanical properties of lap joints;The research temperature and shaping flow behavior of6082-T6aluminum alloy friction stir spot welding of backfilledThe results show:the optimal process parameters of6082-T6aluminum alloy friction stir spot welding as follows:The head rotational speed is1400r/min,the needle retention time is16s,the needle back time is5s;the optimal process parameters of Lyl2aluminum alloy friction stir spot welding as follows:The head rotational speed is1200r/min,the needle retention time is16s,the needle back time is5s.the test Welding joints on microhardness,Test results show that the hardness of6082-T6aluminum and LY12aluminum welding joints showed a W distribution,In6082-T6aluminum alloy welding joints,the microhardness of base metal is highest, the microhardness of heat affected zone is minimum;In LY12aluminum alloy welding joints.the microhardness of plastic zone is highest, the microhardness of heat affected zone is minimum.Using electronic scanning analysis shear fracture,the6082-T6aluminum and LY12aluminum alloy start cracking in in the heat affected zone of joint,6082-T6aluminum alloy joints fracture in the form of ductile fracture,however LY12aluminum alloy joints fracture mixed fracture coexistence of brittle fracture and fracture toughness.The measure temperature of6082-T6aluminum alloy friction stir spot welding joints,The results show:in welding process,Each feature point temperature quickly rises.The temperature lower speed relatively slow. The mixing zone temperature is highest,the probe zone is Followed, in the base material zone,the farther from the outer edge of the sleeves, the lower the temperature.The research three-dimensional flow of6082-T6aluminum alloy friction stir spot welding joints,the cross-section and longitudinal section’s macro-morphology of joint is bowl, the Fe distribute uneven,more Fe distribute in probe zone than other zone;In cross-section,Fe powder in the forward edge less than the back side;In longitudinal section,Fe powder in the forward edge more than the back side,One layer section,Fe distribution is spiraled;The majority of Fe distribute the back side in,however in the forward of joint distribute seldom.The head rotation speed and the depth of head plunged into have some effect on the plastic flow of welding joints,With the head rotation speed increase, the joints plastic metal flow better,With the depth of head plunged into increased, the joints plastic metal flow worse.