Effect Of Local Laser Heat Treatment On The Sheet Formability Of 7B04 Aluminum Alloys

As a typical light-weight material,aluminum alloys have been widely used in aerospace engineering.However,the poor formability of aluminum alloys at room temperature has restricted its application in complex plate components.Recently,local heat treatment has been proposed to obtain tailored heat treated blanks(THTB)with different mechanical properties to improve its formability,but the research on 7-series aluminum alloys is limited.The thesis investigates the effects of local laser heat treatment on the formability of O-state 7B04 aluminum alloy sheet and provides a theoretical basis for the application of local laser heat treatment in the forming of aluminum alloy sheet metal parts.The influence of laser power on the temperature of aluminum alloy sheet was analyzed through laser temperature field simulation and temperature measurement test system,and the reasonable multi-pass scanning distance was determined according to the temperature field distribution.The research showed that when the plate thickness is thinner,the heat treatment heating speed is faster.A linear relationship between the laser power and the highest temperature of heat treatment is discovered.The advantages of laser heat treatment over traditional heat treatment and rapid heat treatment using electrical resistance furnace was discussed.The effect of laser heat treatment on the mechanical properties of the sheets was explained with the microstructure evolution.Results showed that the thin MgZn2 meta-stable phase precipitated by natural ageing treatment played a major strengthening role in the alloy.When the temperature of laser heat treatment was 580?,the strength was significantly improved,with a slight decrease in elongation after fracture.The deep drawing of cup-shaped part was simulated in Dynaform,and the influence of local laser heat treatment on the formability of 7B04 aluminum alloy sheet was discussed with forming experiments.The deep drawing was simulated with rigid punch and hydro-drawing for a kind of complex aerospace frame part.According to the results,a proper heat treatment layout can change the deformation sequence and strain path of the material.Therefore,the formability of the sheet can be improved.When the local laser heat treatment temperature was 580?,the formability of cup-shaped parts was the best,and avhieved the maximum of 41.2%improvement of the limit drawing depth.It is concluded that the local laser heat treatment can successfully increase the formability of frame component during hydro-drawing.