Transient creep characteristics in two Pb–Sn–Zn ternary alloys

Transient creep tests were investigated under different applied stresses ranging from 4.88 to 6.83 MPa near the transformation temperatures for ternary eutectic (Pb–65.5Sn–3.4Zn) and (Pb–65Sn–1Zn) ternary alloys. The transient creep is described by, where εtr=βtn and t are the transient creep strain and time. Both alloys showed enhancement in the creep parameters n and β, a small deviation about (20 K) of the transition point towards low temperature is obtained in comparison to those of binary eutectic Pb–Sn alloy. The role of enhanced diffusion in the enhanced creep region is confirmed. Microstructural analysis confirmed that the mechanism controlling transient creep is a grain boundary sliding (GBS). It was concluded that the Pb–Sn–Zn ternary alloys show superior superplastic behavior compared with the Pb–Sn eutectic composition as a result of the lower melting temperature and the multiplicity of types of interphase boundary causing enhancement in diffusion process.