Disclosed is an interlayer for brazing and diffusion bonding, having a portion as a continuous stratum with an amorphous structure. The amorphous stratum of the interlayer, being ductile, imparts structural integrity to the otherwise brittle alloy composition. Thus, forming and shaping of the interlayer to faying surfaces are improved. In the joining process, the interlayer melts, and on solidifying by cooling or interdiffusion of elements, is converted to a crystalline solid metallurgically bonded to the workpiece. Preferred are flat ribbons with a continuous amorphous surface stratum comprising at least 30 volume percent, and up to 100 percent, of the interlayer.