Details on the Formation of Ti^sub 2^Cu^sub 3^ in the Ag-Cu-Ti System in the Temperature Range 790 to 860 °C

• Published in: Journal of phase equilibria and diffusion Vol. 29; no. 2; p. 156
• Main Authors: Andrieux, J, Dezellus, O, Bosselet, F, Sacerdote-peronnet, M, Sigala, C, Chiriac, R, Viala, J C
• Format: Journal Article
• Language: English
• Published: Materials Park Springer Nature B.V 01.04.2008
• ISSN: 1547-7037; 1934-7243
• DOI: 10.1007/s11669-008-9247-6

Silver-copper-titanium (Ag-Cu-Ti) ternary alloys are often used as active braze alloys for joining ceramics to metals at temperatures ranging from 780 °C (the melting point of the Ag-Cu eutectic) up to 900 °C. When Ti/Ag-Cu joints are brazed at low temperature (near 800 °C), the intermetallic compound Ti^sub 2^Cu^sub 3^ (tetragonal, P4/nmm, a = 0.313 nm, c = 1.395 nm) is systematically missing from the interface reaction layer sequence. An experimental investigation based on isothermal diffusion experiments in the Ag-Cu-Ti ternary system has then been undertaken to clarify the issues of thermal stability and formation kinetics of this compound. Evidence has been found for the stability of Ti^sub 2^Cu^sub 3^ at temperatures ranging from 790 to at least 860 °C. By heat treating Ag-Cu-Ti powder mixtures at 790 °C for increasing times, it has moreover been shown that Ti^sub 2^Cu^sub 3^ forms at a much slower rate than the two adjacent Ti-Cu compounds: TiCu^sub 4^, the first phase to form, and Ti^sub 3^Cu^sub 4^. This explains why although thermodynamically stable, Ti^sub 2^Cu^sub 3^ is not obtained when temperature is too low or reaction time too short.[PUBLICATION ABSTRACT]