The in-situ tensile tests of HFW weld were conducted under scanning electron microscope(SEM)to observe the morphology changes at different positions.During the test,the deformation of sample mainly occurred in the heat affected zone.A large number of slip and necking deformation were generated in the heat affected zone.The nucleation of cracks occurred in the heat affected zone and expanded perpendicular to the tensile direction until to fracture.The fracture of HFW weld sample belonged to ductile fracture,and the main cracks were transgranular type.The formation process included the elastic elongation of sample,intragranular slip deformation,necking deformation,slip step formation and sample cracking.Under the interaction of slip deformation and necking,the slip deformation was accumulated continuously,which was the main reason for crack generation and specimen fracture.
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