The bonding of nickel foam to Ti–6Al–4V using Ti–Cu–Ni braze alloy

A titanium-copper-nickel braze powder is combined with various carrier polymers at a range of loadings and used to braze open cell nickel foams to Ti–6Al–4V plate. The microstructure of the interfaces and the chemical composition are examined, and these are correlated with the mechanical behaviour of the joints, as determined by shear and tensile tests, with the aim being to determine the influence the polymer binder and application method have on the final bond microstructure and properties. The investigations show that, as expected, the binder system used can have an important effect on the amount of oxygen, carbon and nitrogen contained in the braze material, and the mechanical properties obtained. However, the effect is complex, better properties in shear being obtained with an apparently lower quality bond, an observation that is explained by considering the constrained boundary layer formed by the bond. Further Weibull tests show that, although the density variations in the commercially available nickel based foam affect the properties, there is additional variation due to the high degree of process control required to achieve a good bond.