Annealing optimization for tin-lead eutectic solder by constitutive experiment and simulation

For Sn-Pb eutectic solder alloy, uniaxial tensile tests were conducted to dog-bone type specimens annealed at different temperatures (60-180 °C) and durations (2-48 h). Low strain rates ranging from 10^-4 s^-1 to 10^-3 s^-1 were applied to study the competition between creep and plasticity and also the rate dependent effect of annealing condition. It is found that the influence of annealing temperature on material properties is more than that of annealing duration. Higher temperature up to 180 °C generally leads to higher yield and ultimate stresses and ultimate strain of annealed specimens. The optimal annealing condition is suggested to be 180 °C for 6 h for stable and efficient improvements in both strength and ductility. By proposing a concise unified creep and plasticity constitutive model, the sensitivity to strain rate and annealing condition is quantified with consideration of both creep and hardening properties. Parameter calibration theoretically confirms the observed optimal annealing condition in experiments.