An internal variable approach to deformation behavior of a Pb-Sn eutectic alloy

Abstract

A new approach for inelastic deformation has been proposed by utilizing internal variables derived directly from a simple consideration of dislocation dynamics. An extension of the theory to a structural superplasticity has also been made recently by taking the dislocation glide process as the major accommodation mechanism for the boundary sliding process instead of the generally accepted diffusional accommodation. The internal variable theory of structural superplasticity has been successfully applied to the cases of quasi-single phase Al alloys. In this paper, the inelastic deformation behavior of a Pb-Sn eutectic alloy as well as the constituent pure metals has been examined specifically in connection with the internal variable theory. A special attention was focused on the deformation characteristics of the superplastic eutectic alloy, well known to reveal a pronounced {alpha}/{beta} phase boundary sliding. For this purpose, a series of load relaxation tests has been conducted to obtain the flow curves under the condition of a constant structure and the results have consequently been analyzed based on the internal variable theory of structural superplasticity. A method to determine the optimum strain rate for a superplastic forming process has been proposed to this end by the quantitative consideration of PBS and its accommodationmore » process. Additional tensile tests were also performed to verify the results of analysis.« less