The Relationship Between Thermal Deformation Behavior Of Ti6242 And Flash Welding Performance

Titanium and its alloys as one of the materials has irreplaceable excellent performance.Ti6242 alloy,which is near-? titanium alloy,has excellent performance and technology feature.The application of fusion welding techniques to titanium alloys resulted in severe distortion,formation of pores or inclusions,coarse microstructure,thus solid-state joining technologies would appear to be more suitable for joining titanium alloys.In this paper,a 33×55 mm Ti6242 alloy sectional material was joined by flash welding.The microstructure characteristics translation and mechanical properties were studied,the different stage of flash welding and the temperature the hot deformation behavior which affect the microstructure translation after welding were researched,effects of postweld heat treatment on microstructure and mechanical property of Ti6242 alloy and its welded joint were studied deeply.The results show that:1.The microstructure characteristics and mechanical properties in different zone of the welded joints were gotten,and the relationship between microstructure characteristics and mechanical properties were builded.There has no as-cast microstructure in WS and flash welding belongs to solid-state welding,the main structure of WS is Widmannstatten structure,which has stronger intensity and lower toughness than equiaxed structure.Away from the WS,there are deformed microstructure areas by forging,where the phase transition was not happened.The ? and ? phase transition structure were deformed obviously,and the hardness is higher and the impact toughness is lower,relatively.2.The microstructure of different welding stage showed that the formation of equiaxed is not the result of upsetting process in welding but the result of affecting of welding heat cycle and electric pulse.The research of microstructure translation got the model of equiaxed ?-phase translation in heat affected zone : lamella ? translation structure bowed out to grow up from middle to sides,the ? phase boundary between lamella dissolved and disappear,the lamella ? translation structure transform into equiaxed ?-phase.3.The result of heat Treatment is that the lamella ?-phase could not translate into equiaxed ?-phase with the affect of heating temperature,the lamella structure is the ritual growth direction to Ti6242 alloy.And with the increase of heating temperature,the strength increased and the ductility and toughness decreased.4.The microstructure and performance of postweld heat treatment showed that ?-phase decreased and the strength increased,the ductility and toughness decreased with the increase of heating temperature,The slower did the cooling rate of solid solution,the fewer of the titanium alloy martensite content,the lower of the ductility and toughness after aging.With the increase of aging temperature,Ti6242 alloy ductility decreased and the strength increased.The longer of aging,the higher of the strength and frangibility.All in all,the best process program is 960?+2h+AC+590?+8hAC,only in this way Ti6242 alloy got a better comprehensive mechanical property.