Hybrid Tower, Designing Soft Structures

Abstract

The superplastic potential of an aluminium alloy 2124/SiCp composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot extrusion, simple warm rolling has been employed to obtain a fine grained structure before superplastic testing. Constant strain rate tests were performed to characterise the superplastic behaviour of the composite. All tests were performed in air at temperatures of 743-783 K and in the strain rate range 10-3-10-1 s-1. A maximum elongation of 425% was achieved at a temperature of 763 K and a strain rate of 8.3 × 10-2 s-1. The highest value obtained for the strain rate sensitivity index (m) was 0.41. Differential scanning calorimetry was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state. Optical and electron microscopy were used to examine the materials microstructure before and after superplastic testing. © 1998 The Institute of Materials.