Transient creep tests were investigated under different applied stresses
ranging from 3.123 to 6.83 MPa for eutectic (Pb - 65.5 Sn - 3.4 Zn) and (Pb -
65 Sn -1 Zn) ternary alloys. The transient creep is described by εtr = β tn, where
εtr and t are the transient creep strain and time. Both alloys showed
enhancement in the creep parameters n and β. A small deviation about (20K) of
the characteristic point towards lower temperature is obtained in comparison
to that of binary eutectic Pb-Sn alloy. DTA analysis indicates low melting
temperatures in both alloys. It was concluded that the Pb - Sn - Zn ternary
alloys show superior superplastic behaviour 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. Microstructural analysis support the grain boundary sliding (GBS) as
being the mechanism controlling transient creep.