The superplastic deformation behavior of microduplex Pb-Sn alloyshas been investigated in this study. The effect of shape and volumefraction of constituent phases was examined within the framework ofthe recently proposed internal variable theory of structuralsuperplasticity. A series of load relaxation and tensile tests aswell as the observation of deformed surface using the technique ofin-situ straining in a scanning electron microscope were conducted onPb-Sn alloys at room temperature. The flow curves obtained from loadrelaxation tests of the superplastic Pb-Sn eutectic alloy were shownto consist of the contributions from interface sliding (IS) and theaccommodating plastic deformation, regardless of grain sizes. The ISbehavior could be described as a viscous flow process characterizedby the power index value of M_g = 0.5. From a series of surfaceobservation during tensile tests, it was found that the value of M_gwas attributed to the onset of intense phase boundary sliding (PBS).Superplasticity of hypoeutectic alloy (Pb-40 wt./100 Sn), which iscomparable to that of superplastic eutectic alloy, appeared to besuperior to that of hypereutectic alloy (Pb--80 wt./100 Sn).
展开▼
