Metal matrix composites, a smart choice for high damping materials

Abstract

An elegant way to reduce mechanical vibrations in mechanical engineering is to use high damping materials. When high damping must be accompanied by good mechanical properties at high temperature, only high damping metals are available. High damping metallic materials that are useful in mechanical engineering have to exhibit, simultaneously, good mechanical properties and a high damping capacity. The development of such materials is possible only when the microscopic mechanisms responsible for internal friction are independent of the mechanisms that control the mechanical strength. One way of achieving such a compromise is the use of two-phase composites, in which each phase plays a specific role: damping or strengthening. Magnesium matrix composites are good examples. Unidirectional solidification of Mg–2 wt% Si alloys yields Mg 2Si/Mg composites with a mechanical strength as high as industrial magnesium cast alloys (AZ63) with a damping capacity 100 times higher. Moreover, Mg–2 wt% Si alloys reinforced with long carbon fibers have a specific Young’s modulus of ∼200 GPa with a damping capacity of 0.01 for a strain amplitude of 10 −5.