INTERFACIAL STRUCTURES AND MECHANICAL-PROPERTIES OF STEEL-NI AND STEEL-TI DIFFUSION BONDS

Static and fatigue shear tests of steel-Ni bonds and steel-Ti bonds we re carried out to obtain the relations between the strengths and the b onding conditions. Ultrasonic measurements were also made to examine t he relations between the strengths and the size of the bonded region ( the estimated diameter). At the bonding interface of the steel-Ni bond s, no intermediate phase was observed. At the bonding interface of the steel-Ti bonds, a thin layer of intermetallic compound was formed at lower bonding temperatures but, at higher bonding temperatures, the in terlayer melted and the bonding interface became rough. The intensity of the ultrasonic wave reflected from the bonding interface changed, d epending on the state of the bonding interface. In shear tests of the steel-Ni and steel-Ti bonds, cracks propagated along the bonding inter face, and the strength was proportional to the square of the estimated diameter. In fatigue tests, cracks propagated in the thickness direct ion of the plate and no relation was obtained between the fatigue life and the estimated diameter. Fatigue life distributions were represent ed by two-and three-parameter Weibull distributions.