Investigation of high-temperature plastic deformation using instrumented microindentation tests. Part II: The deformation of Al-based particulate reinforced composites at 473 K to 833 K

Constant-load pyramidal indentation tests were performed from 473 K to 833 K on P/M fabricated 2024 aluminum reinforced with either SiO2, SiC, or Al2O3 particles to investigate the influence of particulate reinforcement on the high-temperature plastic deformation process during indentation. The composites all displayed larger apparent threshold stress σth than the previously reported unreinforced P/M 2024 aluminum alloy. SEM investigation of the indentations indicated that the indentation process is accompanied by considerable cracking and interfacial debonding of the reinforcing particles, the extent of which increases with increasing temperature. The magnitude of σth was largest for the Al2O3 reinforced composite and this is attributed to the load-transfer that occurs when the indenter contacts the reinforcing particles and the superior high-temperature interfacial strength of this composite. The apparent activation energy G0 of the indentation strain rate increased from 0.25μb3 at 473 K to 0.60μb3 at 833 K. These values are within the expected range for weak particles and dislocation-dislocation interactions but are lower than the previously reported 0 of the unreinforced P/M 2024 alloy. We conclude that the low indentation strain rate of the particulate reinforced composites is the result of the load transfer due to the presence of the reinforcements and its affect on increasing the σth. The low values of G0 are consistent with our observation that extensive particle cracking and interfacial debonding occur in the reinforced material during indentation. C 2006 Springer Science + Business Media, Inc.