SUPERPLASTICITY IN AN ALUMINUM-ALLOY 2124 SICP COMPOSITE/

The superplastic potential of an aluminium alloy 2124/SiCp composite, fabricated by powder metallurgy techniques, has been investigated. Ins tead of any special thermomechaizical processing or hot extrusion, sim ple warm lolling has been employed to obtain a fine grained structure before superplastic testing. Constant strain late tests were performed to characterise the superplastic behaviour of the the composite. All tests were performed in air at temperatures of 743-783 K and in the st rain I rate range 10(-3)-10(-1) s(-1). A maximum elongation of 425% wa s achieved at a temperature of 763 K and a strain late of 8.3 x 10(-2) s(-1). The highest value obtained for the strain rate sensitivity ind ex (m) was 0.41. Differential scanning calorimetry was used to ascerta in the possibility of any partial melting in rite vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took pl ace entirely in the solid state. Optical and election microscopy were used to examine the materials microstructure before and after superpla stic testing. MST/4023.