Abstract: A method is provided for achieving predetermined thickness requirements throughout a superplastically formed structure having extreme contours. A laminate assembly of sheets of a metal capable of exhibiting superplasticity, such as titanium alloy, is formed by a combination of superplastic forming and diffusion bonding. The shapes and positioning of the sheets is selected to provide extra metal where the greatest degree of stretching is necessary, such as around the lobes of an exhaust mixer for a turbofan aircraft engine. The gauge can thus be controlled throughout the structure while avoiding weak points and undue weight.

Abstract: A method of diffusion brazing two or more titanium alloy metal parts, such as sheets, thick sections or a honeycomb core to one or two face sheets, to form a unitary panel. A low melting copper-nickel layer is interposed between the faying surfaces of two parts to be bonded. The layer may be a foil placed between the surfaces or may be a layer plated onto one or both surfaces. The assembly is heated to at least the eutectic melting temperature of the base metal-interlayer eutectic point for a time sufficient to permit effective wetting and diffusion bonding of the surfaces. The assembly is held at the elevated temperature a sufficient additional time so as to allow isothermal solidification to occur. The assembly is then cooled, resulting in a unitary structure. This method is particularly effective with titanium aluminides face sheets and a titanium aluminide or other titanium base honeycomb core and with an interlayer consisting essentially of nickel and copper.