Intermetallic formation in a Ti–Cu dissimilar joint brazed using a Zr-based amorphous alloy filler

Microstructural evolution of the Ti–Cu dissimilar joints brazed by a Zr 41.2Ti 13.8Cu 12.5Ni 10.0Be 22.5 (at.%) amorphous alloy filler was investigated at a temperature of 820 °C for 1–20 min. As the brazing time increased, the overall composition of the joint sensitively changed from Ti-rich to Cu-rich owing to the different reactivity of the Zr in the filler with the Ti and Cu in the base metals. Based on such time-dependent compositional change, the formation of the intermetallic phases in the joint was basically divided into three stages; Stage (1): formation of interfacial Ti 2Cu, Stage (2): formation of two-phase structure with Ti 2Cu/TuCu and Cu 2TiZr, and Stage (3): transformation to Cu-rich phases. At Stage (2), the joint was fully produced isothermally by directional phase transformations with fine dendritic and columnar two-phase structures, revealing the highest bonding strength due to its controlled intermetallic morphology.