TWI Industrial Member Report Summary 102/1979
By S Elliott, E R Wallach and I A Bucklow
A study of the interface surfaces of fractured diffusion bonds in a mild steel was made in order to further understanding of the mechanisms of bond formation and of the mechanical properties of such bonds. The results show that parent-metal tensile strengths are achieved with some 20% of the interface still unbonded and that these unbonded areas are present as grooves rather than as isolated voids as had previously been thought. The relative orientation during bonding of any directional surface finish on the two component halves affects the geometry of the unbonded grooves and, to a slight extent, the resultant tensile strengths. The results also suggest that tensile testing alone is not a sufficient criterion by which bond quality should be assessed; impact or fracture toughness testing also must be considered.