Numerical and experimental analysis of creep deformation and stress-relaxation in Sn-5Sb lead-free alloy

Abstract

In-service performance of solder alloys is highly dependent on its high temperature behaviors like creep and stress relaxation. In this investigation, creep behavior of Sn-5Sb alloy is studied using three integrated creep equations, i.e., combination of power-law and omega model (PO), exponential and omega model (EO), and logarithmic and omega model (LO). In addition, stress relaxation (SR) curves are derived using two approaches of spring-dashpot (SD) and Peleg (P) model to establish the best fit to experimental data. Required creep data were attained using creep tests at several stresses at 500 K while relaxation ones were carried out under a constant strain of 0.5% at 300, 330, 360 and 400 K. Nonlinear least-square fitting (NLSF) analysis was carried out to deliver the best fit of the experimental data and recognition of constants for each equation. Results showed that in the lower stress level of 160 MPa, the CEO model presents a better fitting of experimental creep data with respect to CPO and CLO, whereas, CPO is with superior accuracy in the higher stress regions. In SR mode, SD model did not indicate good performance at 500 and 550 °C while showing good accordance with the experimental data at 600 and 650 °C. P model on the other hand, was superior to SD model in overall temperature range as obtained parameter values followed temperature dependence quite well. It is concluded that the EO and P models can accurately predict the creep and relaxation behavior of Sn-5Sb solder alloy, respectively.