1986 Volume 4 Issue 1 Pages 125-130
Mechanism of ductility-dip cracking in weld metal of Invar (Fe-36%Ni alloy) reheated by following welding, pass was studied from the viewpoints of grain boundary precipitation and grain boundary serration. Main conclusions obtained areas follows: (1) Temperature dependency of amount of precipitates on the fracture surface, has good correlation with the characteristic of hot ductility. (2) The fracture surface of the specimen having low crack susceptibility has comparatively little amount of precipitates. (3): The features of intergranular fracture surface under different testing temperature and crosshead speed have intimate connectionn with that of grain boundary serration, and thus this suggests strongly. that grain boundary serration has an important role on'the ductility-dip crack. (4) Thus it is judged that both grain boundary precipitation and grain boundary serration cause cavity foi nation cooperatively accompanied by grain boundary sliding. (5) The mechanism of ductility-dip cracking was proposed synthetically from the viewpoints of grain boundary sliding, grain boundary serration, grain boundary precipitation, grain boundary migration, deformation stress and recrystallization.