Microstructure and Dynamic Mechanical Properties of Ti6321 Alloy TIG Welded Joints
Tungsten inert gas(TIG)welding was used to weld the Ti6321 alloy with bimodal microstructure,and the microhardness and static and dynamic mechanical properties of the unwelded base metal,near heat affected zone base metal,heat affected zone and weld metal were tested.The microstructure of the welded joint before and after dynamic compression was observed.The results show that after TIG welding of Ti6321 alloy,the microstructure of the heat affected zone is a nearly bimodal microstructure composed of equiaxed primary α phase and β phase+acicular martensite α'phase.The weld metal has a basket microstructure composed of large blocky α phase and acicular martensite α'phase,while the grains are relatively coarse.The microhardness and static and dynamic compressive strength show that the heat affected zone of welded joint is the highest,followed by the base metal and the base material near heat affected zone,and the weld metal is the lowest.The energy of impact absorption of the base metal near the heat affected zone and the heat affected zone is similar,while the weld metal is the lowest.Due to the formation of dense and fine acicular martensite α'phase in the heat affected zone,its hardness and dynamic compressive strength are high,and its deformation coordination ability is weak,which result in poor plasticity.The coarse grains in the weld metal induce low dynamic plasticity and dynamic strength.When the dynamic compressive strain rate in the range of 2100～2900 s-1,the base metal,heat affected zone and weld metal undergo obvious plastic deformation as the strain rate increases.The equiaxed α phase in the base metal and the heat affected zone changes from uniformly distributed ellipsoid before compression to long strip with different directions,and the degree of transformation increases with the increase of strain rate.
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维普
