Abstract
Superplasticity in a doubly extruded magnesium based composite, ZK60 reinforced with 17 vol.-%SiC particles, was investigated. The influences of strain rate on the flow stress and elongation in the composite were characterised. It was found that the composite exhibited superplasticity (elongation > 400%) at high strain rates (∼ 0.1 s−1). In addition, the material showed a high strain rate sensitivity of 0.5 and an activation energy of 81 kJ mol−1 in the superplastic region. Based upon these results, it was proposed that the dominant deformation mechanism is grain boundary sliding accommodated by a grain boundary diffusion process. A comparison of the superplastic behaviour was also made between the doubly extruded and singly extruded composites.
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