Superplasticity of Fine-Grained 20VOL%SiC Whiskers Reinforced 2024 Aluminum Alloy Produced by ECAP with a Rotary Die
Squeeze-cast 20vol%SiCw/2024 composite was processed by rotary-die equal-channel angular pressing (RD-ECAP) and tensile-tested at elevated temperatures. RD-ECAP does not require billet removal and reinsertion between ECAP passes and can produce large cumulative deformation of type A in the billet at a controlled extrusion temperature. Tensile specimens were machined from the RD-ECAP processed billets along the longitudinal direction. 16 RD-ECAP passes at 623 K produced an average matrix grain size of about 0.8 μm in the composite. The ECAP processed 20vol%SiCw/2024 composite exhibited 330% elongation to failure when tested at 783 K and the high strain rate of 1.17×10-1 s-1. The values of strain rate sensitivity exponent of the SiCw/2024 composite determined over the strain rates between 10-2 and 1.0 s-1, was 0.39, 0.47 and 0.53 at 763, 773 and 783 K, respectively. The grain sizes of the aluminum alloy matrix in the composite after superplastic deformation increased from 0.8 μm to be about 1.5 μm. There was no cavity found within the uniformly deformed area. The apparent activation energy for the superplastic deformation of the 20vol%SiCw/2024 composite was determined to be 284 kJ·mol-1.
T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran
A. B. Ma et al., "Superplasticity of Fine-Grained 20VOL%SiC Whiskers Reinforced 2024 Aluminum Alloy Produced by ECAP with a Rotary Die", Materials Science Forum, Vols. 539-543, pp. 2934-2939, 2007