Impression relaxation and creep behavior of Al/SiC nanocomposite

In the present study, Al-4 % of volume fractions of SiC composites were produced by mechanical alloying and the powders were gradually compacted at a pressure of 620 MPa. The post-compaction samples were sintered under an argon atmosphere at 873 K and the corresponding creep results were obtained from impression-relaxation. Additionally, compression techniques were investigated at high temperature (723 K). Enforcement rates of 8.3 x 10(-3) and 0.83 x 10(-3) mm s(-1) and indenter depths of 0.5 mm and 0.8 mm were selected. Results showed a constant relation between stress relaxation and compression creep rate. Under different conditions of impression-relaxation this constant was 1000 for compression stress of 30 MPa and 32.5 MPa, and 400 for compression stress of 35 MPa, subsequently. This coefficient was affected by the porosity and was stable for different indenter depths and enforcement rates. The variations in the steady state relaxation rate were reasonable because of different nano-SiC distributions and porosities in the form of drops. Moreover, in spite of the enforcement rate decrease, the nanosized reinforcing particles caused a decrease of the relaxation rate. It should be mentioned that the constant coefficient calculated will be useful to estimate the fracture time which uses the strain rate calculated from impression-relaxation in industrial applications.