Evaluation of heat damage on B4C particulate reinforced aluminum alloy matrix composite using acoustic emission techniques

The effects of prolonged heat damage on the tensile properties of aluminum alloys reinforced with B4C particle of average particle size of 10.5 and 20.9 mm was investigated by both mechanical and acoustic emission monitoring during tensile test. To ensure the matrix contribution was similar for all specimens, specimens were heat treated to the same condition for each material after heat damage. The particle/matrix bond strength was found reduced significantly despite what was reported in the literature of stable particle/matrix interface at temperature lower than 660°C. The micromechanisms of fracture changed from particle fracture and debonding, for as received specimens, to particle/matrix debonding after exposure to high temperature. The cumulative acoustic emission (AE) events during post heat exposure reduced with the increase of heat damage on the specimen. A Weibull probability distribution function that incorporates heat damage and is related to the cumulative AE events is developed. This model could be used to evaluate the heat damage by subjecting the heat damaged specimen to a tensile test while collecting AE data up to a strain level ε. The total events can then be used in connection with the model to predict the extent of the heat damage to the particle/matrix interface. The results indicate that the tensile strength was little sensitive to the particle/matrix bond strength.