Effect of Thermal and Cryogenic Conditioning on Flexural Behavior of Thermally Shocked Cu-Al2O3 Micro- And Nano-Composites

Abstract

This investigation has used flexural test to explore the effect of thermal treatments i.e. high temperature and cryogenic environments on the mechanical property of Al2O3 particulate reinforced Cu metal matrix micro- and nano-composites in ex-situ and in-situ conditions. Cu-5 vol. % Al2O3 micro (10μm)- and nano (<50 nm)-composites fabricated by powder metallurgy route were subjected to up-thermal shock cycle (193 K to 353 K) and downthermal shock cycle (353 K to 193 K) for different time periods followed by 3-point bend test. One batch of specimens (micro- and nano-composites) was conditioned at 353 K temperature and 193 K temperature separately followed by 3-point flexural test. High temperature flexural test was performed at 373 K and 523 K temperature on the micro- and nano-composites. All the fractured samples obtained after various thermal treatments were studied under scanning electron microscope (SEM). The development of thermal stresses quite often results in concentration of residual stresses at the particle/matrix interface eventually weakening it. Enhancement of flexural strength was recorded for down- as well 3 as for up-thermal shock in microcomposites. The high temperature flexural strength of micro- and nano-composites is lower than at ambient temperature. The amelioration and declination in mechanical properties as a consequence of thermal shock, thermal conditioning and high temperature flexural testing have been discussed in the light of fractography.