Effect Of Heat Treatment On Microstructure Evolution And Dynamic Deformation Behavior Of GH4169 Welded Joint

With the rapid development in the aerospace field,improvement on the thrust-weight ratio as well as service security attracted more and more attention in the aircraft engine manufacturing industry.Many key engine components are welding structures and will inevitably emerge tissue deterioration in the connection joint while bearing the high-speed impact load.It has been found that the mechanical behavior and deformation behavior of metal materials under impact load changed significantly compared to the quasi static conditions,therefore it is necessary to reflect how strain rates affect the deformation behavior of GH4169 laser welded joint.This paper focused on studying the microstructure evolution of GH4169 laser welded joint in the simulated environment with different heat treatment,revealing the influence of strain rates on tensile deformation behavior of GH4169 welded joint in standard heat treatment state and long-term aging state.The research results show that,the Laves phase appeared in the welding process can be eliminated and ?" and ?' phase can precipitate uniformly under 1020? solid solution and double aging process,so the strength and plasticity can be matched well in the laser welded joint.After long-term aging at 680?,granular ? phase grows into short rod and long needle,at the same time its size and volume fraction increases along with the time prolonged,while globular y" phase grows into the disc,coarsening and translates into 8 phase.Compared with the welded joint in standard heat treatment,the microhardness of long-term aging GH4169 welded joint decreases and the softening zone is not obvious.As to GH4169 welded joint under 1020? standard heat treatment,when strain rates range from 10-3s-1 to 500s-1,both yield strength and tensile strength increase rapidly with the strain rate growing,this phenomenon can be explained by strain rate hardening theory.With strain rate increasing,the elongation gets its minimum value at the strain rate of 100s-1,then has a dramatic rising,this is because the main mechanism of plastic deformation is dislocation gliding under standard static condition,while under dynamic condition,there are lots of deformation twinning besides dislocation sliding.With strain rate increasing,the strength of long-term aging GH4169 welded joint increases,which can be explained by strain rate hardening theory.Elongation shows downward trend,because there is a number of larger size precipitates emerging gradually under high strain rates,resulting in the poor deformation coordination;with the increasing of aging time,? phase grows up rapidly and y" phase coarsening,there are no obvious boundaries between fusion zone and HAZ(heat affected zone),which lead to an increase in the plasticity to some extent.