Thermal Expansion Response and Dynamic Mechanical Behaviors of A1/B4C Composites at Low Temperatures

The thermal expansion response and dynamic mechanical property of a 30 Vol.% boron carbide (B 4 C) particulate reinforced Al 6061 composite, fabricated by plasma thermal spray technique, was studied in this paper. For composite sample not annealed, thermal cycling to the sub-ambient temperature (-70°C) will result in unstable thermal expansion response, notably in a significant hysteresis loop. The reasons for this unstable thermal expansion response were discussed in detail. The heat-treatment of the composite was found to have significant effect on the thermal expansion response of the composite. Finally the dynamic mechanical property of the composite was studied. The result showed that the elastic modulus of the AI/B4C composite could remain unchanged at low vibration frequency. However, at the vibration frequency higher than 75 Hertz, the elastic modulus of the composite tends to decrease with the increase of vibration frequency.