中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 35 No. 4 April 2025 |
（1. State Key Laboratory of Precision Welding & Joining of Materials and Structures, Harbin Institute of Technology, Harbin 150001, China;
2. Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou 450041, China;
3. Beijing Institute of Control Engineering, Beijing 100094, China）
Abstract:The inherent brittle behavior and ductile-to-brittle transition (DBT) mechanism of Sn-3.0Ag-0.5Cu (SAC305) solder alloy at the liquid nitrogen temperature (LNT, 77 K) were investigated through uniaxial tensile experiments conducted at different temperatures. Dynamic recovery and recrystallization of SAC305 solder alloy at room temperature (RT, 293 K) activate a softening process. Conversely, intersecting and none-intersecting deformation twins, embedded in body-centered tetragonal Sn, enhance tensile strength and stabilize strain hardening rate, while suppressing the elongation of the alloy at LNT. The irreconcilable velocity difference between twin thickening (~8 μm/s) and dislocation slip (~4 μm/s) results in premature brittle fracture, during the linear hardening and DBT. Moreover, the secondary phases degrade the mechanical property of SAC305 solder alloy, and micro-cracks appear between Cu6Sn5 and Ag3Sn in the eutectic matrix.
Key words: SAC305; deformation twinning; secondary phases; tensile property; cryogenic temperature
