Solid/Solid State Interfacial Reactions in the Sn-9Zn/Cu-Based Alloys (C1990 HP, Alloy 25, and C194) Couples

We investigated the kinetics of the intermetallic compound (IMC) growth during the solid/solid state reaction at 125-175 degrees C for 100-2000 h between Sn-9 wt.% Zn (SZ) with Cu-3.28 wt.%Ti (C1990 HP), Cu-2.0 wt.% Be (Alloy 25), and Cu-2.3 wt.% Fe (C194) alloys, respectively. The results revealed that both the CuZn5 and Cu5Zn8 phases were formed at early stage and the CuZn5 phase was transformed to the Cu5Zn8 phase when the aging temperature and time were increased in the SZ/C1990 HP couples. The CuZn5 and Cu5Zn8 phases were formed, and no phase transformation was observed in the SZ/Alloy 25 couples. In the SZ/C194 couples, only Cu5Zn8 phase formed at early stage of aging. The Sn tunneling phenomena promoted Cu-Sn IMC formed at a higher temperature and longer aging time. The Cu6Sn5 phase was formed around the Sn-rich matrix and consumed the Cu atom from the C194 substrate. A diffusion-controlled mechanism was responsible for IMC growth in all couples. The activation energy for overall IMCs was 51.1 kJ/mol on SZ/C1990 HP, 45.7 kJ/mol on SZ/Alloy 25 couples, and 87.0 kJ/mol on SZ/C194.