Study On The Microstructure Of TC4Joints Welded By Linear Friction Welding

It is essential to improve the aero-engine thrust-weight ratio to improve the operationalperformance of the aircraft.And the weight of the engine is the key factors. Linear frictionwelding as a high efficient, advanced, precision connection method, Used in the manufactureof titanium alloy blisk, make the rotor blades and engine roulette welding into one, Theweight of the engine is reduced greatly. So, The process of welding and weld quality willdirectly affect the overall performance and reliability of the blisk..The microstructure and substructure of TC4alloy joints welded by LFW wereinvestigated in this paper. and microhardness distribution of the joint was tested. The resultsshow that：the welded joint can be divided into three zones: base metal zone, thermo affectzone (TMAZ) and weld zone. The TMAZ present a gradience organization from the distanceof weld center, The TMAZ zone can be divided into A、B and C areas according to thedifferent organization，equiaxed α and lamellar (α+β) be elongated in forced direction in Aarea, deformation and α recrystallization and a little secondary α in B area, the αrecrystallization α+β and martensite organization in C area. The microstructure at the weldzone is acicular α′. And the martensite directions are not completely different，In the localarea the martensite is consistent position. Through the analysis of dynamic recrystallizationprocess in the welding joints, only the α happened dynamic recrystallize in TMAZ, diameterof Recrystallization grain is about1um or so. acicular martensites in weld zone is from theβphase recrystallization through phase change.The form of substructure is various in Joints,The substructure of TMAZ is mainly dislocation, and a small amount of stacking fault andtwins. The substructure of martensite in weld zone is twins and low density of dislocation.The hardness test show that the microhardness gradually increases from360HV to390HVfrom the center to base metal in the direction perpendicular to the weld seam. Longitudinalmicrohardness of the weld zone gradually reduces to about330HV from the center to edge.