Effects of secondary phases on the damping behaviour of metals, alloys and metal matrix composites

An understanding of the precise correlation between the presence of secondary phases and material damping has eluded investigators, partly as a result of the fact that often there are various mechanisms involved. As a step towards the clarification of damping phenomena in metals and alloys, this paper provides a systematic review of the studies that have been completed on the damping mechanisms present in metals and alloys, with particular emphasis on precipitation. The damping mechanisms associated with secondary phases in metals and alloys have been subdivided into four categories, namely interface damping theory, thermal mismatch-induced dislocation damping theory, interaction damping theory and the rule of mixtures damping theory. A number of alloy systems are discussed to demonstrate the applicability of the four types of theory and the level of understanding of these complex mechanisms. As an extension of precipitation damping theory, the damping behaviour and mechanisms in particle-reinforced metal matrix composites are extensively discussed.