Assessment of particle–matrix debonding in particulate metal matrix composites using ultrasonic velocity measurements

Abstract

Particulate metal matrix composites are a class of materials that have evoked keen interest, largely due to the promise of improved properties over conventional metals and alloys. However, the effective realization of the improved properties of these composites is contingent upon the presence of good bonding between the reinforcement particles and the metal matrix. Therefore, a quantitative measure of the particle–matrix bonding efficiency would be particularly useful in helping to fully realize the potential of these materials. It is known that particle–matrix debonding degrades the elastic modulus of the composite considerably while having practically no effect on its density. Based on this, a model has been developed and a quantitative measure of debonding has been proposed. In conjunction with measurement of ultrasonic velocity, this model is capable of giving quantitative estimates of the debonding factor of the composite material. In the present study, aluminum alloy A356–SiC p composites containing between 3 and 15 vol.% SiC particles have been synthesized by the melt stirring method. Debonding factors as high as 0.29 have been estimated in low SiC volume fraction composites. In the case of the high SiC volume fraction composites, the estimated debonding factor was found to be as low as 0.10, corresponding to the lesser particle–porosity interaction observed in these composites. Elastic modulus measurements on composite specimens also confirm the observation that particle–porosity association is seen to a greater extent in the low SiC volume fraction composites. Elastic modulus deviation of up to 14% was observed in the case of the low SiC volume fraction composites while the high SiC volume fraction composites showed a maximum modulus deviation of less than 10%. It was also seen that measurement of debonding factor before and after hot rolling of the composites provides a method of evaluating the effectiveness of the rolling operation in improving the integrity of the composites.