High-strain-rate superplasticity of an Al–4.4Cu–1.5Mg/21SiCW composite sheet

High-strain-rate superplasticity (HSRS) of an Al–4.4Cu–1.5Mg/21SiCW composite sheet was evaluated by tensile tests and microstructural characterization over a range of initial strain rates from 1.67×10−3 to 1.67×100 s−1 and temperatures from 723 to 818 K. The strain rate sensitivity exponent of the composite was found to be approximately 0.34 at a strain rate of 10−2–100 s−1 and at temperatures between 723 and 818 K. From the experimental findings, the strain rate sensitivity exponent is almost constant during deformation. A maximum elongation of ≈446% was obtained at 3.33×10−1 s−1 and at 793 K, which is near the partial melting temperature of the composite. The threshold stress is strongly temperature dependent. The cavitation behavior of the composite during deformation was also examined and compared with that of a typical superplastic aluminum alloy (Al7475). The experimental results revealed that the cavity growth was essentially plastic-controlled. It was suggested that the presence of liquid phase was beneficial to nucleation at the interfaces and limited the rate of cavitation growth.