Amorphous Ribbon Brazing Filler Metals: Selection Criteria, Glass Formation, and Transient Liquid Phase Bonding

Amorphous ribbon brazing filler metals produced by rapid melt quenching form a distinct class of high-temperature brazing materials; a few ductile microcrystalline ribbons are treated as boundary cases. This review systematizes the four industrial families of such fillers: copper-phosphorus (Cu-Ni-Sn-P), titanium (Ti-Cu-Ni, Ti-Zr-Cu-Ni(-Be)), zirconium (Zr-Ti-Cu-Ni, Zr-Cu-Fe-Be), and nickel-metalloid (Ni-Cr-Si-B, Ni-Cr-P) alloys, together with the closely allied iron-based fillers. This selection is no accident: to become the basis of a commercial filler metal, an amorphous alloy must simultaneously satisfy five criteria (C1-C5) of brazing temperature, glass formation, base-material compatibility, ribbon manufacturability, and cost and safety, which are formulated here as a single cross-system checklist with operational thresholds. The class itself exists because in deep eutectics, the depressant and glass-former functions can coincide. Transient liquid phase (TLP) bonding, for which the thin homogeneous ribbon is a particularly suitable carrier, runs through the review as a unifying thread. The structural heredity of the ribbon-derived melt and the complementarity of the families by base material are discussed; ductile silver and aluminum fillers serve as a negative control delineating the boundary of the class, and the criteria are applied predictively to compare the families and to select a filler metal for a specific task.