Research On Laser Welding Process And Orgnization Performance Of TC4/Ti22Al25Nb

TC4 and Ti2AlNb alloy are widely used in aerospace and other fields.Ti22Al25Nb is a new type of titanium alloy with O phase,and it has good application prospect,but there are many problems in laser welding of TC4 and Ti2AlNb alloy,such as coarse grains of welded joint,uneven distribution of elements and difficulties in welding of 1mm thick TC4/Ti22Al25Nb,therefore,in addition to study the microstructure and properties of laser welding of TC4/Ti22Al25Nb,the grain refinement and elemenst homogenization of the joint under ultrasonic vibration are qualitatively analyzed,these works have important engineering application and research value.1 mm thick TC4 and TC4/Ti22A125Nb welding experiment are carried out by using the optical fiber laser processing system,through Simple Variable Method,the effect of welding power and ultrasonic vibration on the organization and performance are studied,and then the following main conclusions can be concluded:(1)When the welding speed remains at 3mm/s,excellent TC4 and TC4/Ti22A125Nb welded joints can be geted with 850W and 800W,there is no big change of lap joint when power increases from 810W to 830W.(2)In terms of microstructure,the weld zone of TC4 mainly is martensite structure,HAZ is the same as the weld zone,weld zone and HAZ can be divided as coarse grain and fine grain area,and ultrasonic vibration can refine grain size.The main phase in weld zone of the TC4/Ti22Al25Nb is the B2 phase,and there are sone precipitated phase around the grian boundary,and there are some cracks near TC4 side.(3)The hardness of the weld zone is higher than that in HAZ,and the hardness of the base metal is the lowest.The TC4/Ti22A125Nb butt joint and lap joint have the same trend as TC4,the microhardness of weld zone near the HAZ of TC4 is highest,and the HAZ of TC4 is higher than the base metal.Ultrasonic vibration can improve the hardness due to it can refine the grain of the welded joint(4)The tensile strength of TC4 joint and TC4/Ti22A125Nb weld butt can be improved by applying ultrasonic vibration during the welding experiment,the morphology of fracture mianly is river pattern and cleavage step.(5)Ultrasonic vibration can effectively avoid the existence of c coarse grain in the weld zone;in addition,it is proved that ultrasonic vibration can change the uneven distribution of welded joint elements by means of EDS.