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-34Zn) and (Pb-65Sn-1Zn) ternary alloys. The transient creep is described by, where epsilon (tr) = betat(n) and t are the transient creep strain and time. Both alloys showed enhancement in the creep parameters n and beta, 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. (C) 2001 Published by Elsevier Science BN.