The dynamic and static mechanical characteristics of Sn-7Zn-based solder alloy modified with microalloying of In, Fe and Co elements

Abstract

AbstractTensile creep experiments and pulse-echo overlap (PEO) method were utilized to analyze the impact of small additions of 2.5%wt In, Fe and Co (0.1%wt for each) on the creep resistance and elastic properties of a cast Sn-7Zn alloy. The In-modified alloy displays noticeably enhanced creep resistance and increased the fracture time (~ 2.7 times) due to precipitation strengthening and formation of γ-InSn4 particles. The In-modified alloy exhibits an as-solidified grain structure, which is finer than the Sn-7Zn alloy, and predicted to enhance deformation resistance by lattice self-diffusion creep. Nonetheless, the creep resistance of Sn-7Zn alloy deteriorates after Fe and Co addition, highlighting the excellent coarsening of the new γ-Zn21Co5, γ-Co2Sn2Zn, and α-Fe0.92Sn0.08 precipitates. The obtained results implied that the creep strain rate follows the Garofalo hyperbolic sine equation, and the computed creep stress exponent is consistent with a climb-controlled dislocation creep. Consequently, for all PEO tests, the values of resulting Young's modulus (E) (66.7 GPa) and shear modulus (G) (20.5 GPa) of In-modified Sn-7Zn alloy were superior to those of the conventional plain Sn-7Zn alloy and Fe and Co modified alloy in its cast condition.