Cavity closure during compression between semi-closed dies using superplastic tin-lead alloy

Superplasticity is a feature of a material or alloy, which allows the material to deform plastically to an extremely large strain at low values of stress under certain loading conditions of strain rate and temperature. Eutectic tin-lead alloy is a practical material for research investigations as it possesses a superplastic behavior at room temperature and low strain rate which makes it a useful tool in simulating the ordinary engineering materials at high strain rate and temperature, and has been extensively used as a model material. In this paper, superplastic tin-lead alloy was used at room temperature to simulate the closure of cavities in steels at high temperatures in the hot region under dynamic loading (high strain rate) under the effect of compressive loads using semi-closed dies (modified dies) with 45^o inclination and compare the results from these dies with those of flat platens (open dies) published previously. Hollow specimens having different values of bore diameter (D_b) to outer diameter (D_out), of the same height and volume were investigated under 40% height reduction. The cavity closure for each specimen was determined. Comparison is made between flat platens and semi-closed dies regarding cavity closure based on bore diameter, bore volume, reduction percentage in bore diameter and reduction percentage in bore volume, at the 40% reduction in height. It was found that modifying the platens (45^o inclination) resulted in lower values of bore diameters and volume i.e. higher values of reduction in bore diameters and volumes percentages irrespective of the value of bore diameter and the ratio of D_b/D_out.