Microstructure and Dynamic Mechanical Response of Ti6321 Alloy Welded Joint
The mechanical response of Ti6321 alloy TIG welded joint under dynamic compressive load was studied.The microstructure and dynamic mechanical response of welded joint under high strain rate of 2000～2800 s-1 were studied,combined with optical microscopy,scanning electron microscopy,electron backscatter diffraction and transmission electron microscopy.The results show that the grain size of Ti6321 alloy welded joint gradually increases from base metal(BM)to weld metal(WM),and the microstructure transits from bimodal of BM to widmanstatten structure of WZ.The equiaxed α phase in the heat affected zone(HAZ)gradually shrinks,and coarse α phase appears in WM.Under dynamic compressive loading,HAZ and BM have higher yield strength,while the flow stress and yield strength of WM are lower.Under the strain rate of 2400 s-1,the strain rate sensitivity factors of each region show a downward trend with the increase of strain.When the strain is 0.05,the strain rate strengthening effect gradually increases from WM to BM.After dynamic compressive loading,the microstructure of each region of welded joint undergoes certain flowing deformation and grain breakage.The grain deformation in HAZ is more,and the grain deformation in WM is less.After dynamic compression,the dislocation density and twin content both increase.
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