Microstructure and Low-cycle Fatigue Properties of TC17/Ti60 Dissimilar Titanium Alloy Laser Welded Joint
Laser welding was carried out on TC17/Ti60 dissimilar titanium alloy,and the macro morphology,microstructure,microhardness,tensile properties and low-cycle fatigue properties of the welded joint were studied.The results show that there are large differences in microstructure among the base material(BM),weld zone(WZ)and heat-affected zone(HAZ)of TC17/Ti60 alloy welded joint.The TC17 titanium alloy BM is α+β two-phase structure,and there are lots of secondary α′phases in β phase.Ti60 BM structure is mainly composed of equiaxed α phase,and β phase is mainly distributed around the equiaxed α grain.The microstructure of WZ is acicular secondary α′phase.With the decreases of the distance to the center of WZ,the α′phase in the TC17 HAZ gradually disappears,the α phase gradually changes to β phase,and theβ phase in Ti60 HAZ gradually disappears and the α phase gradually changes to the acicular secondary α′phase.The tensile fracture location of TC17/Ti60 alloy welded joint is in TC17 HAZ.There are porosity defects in the lower part of the WZ of TC17/Ti60 alloy welded joint,which lead to the fracture location is in the WZ under the low-cycle fatigue test.
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