Magnesium Alloys Based Composites

Abstract

Metal matrix composites offer a wide range of opportunities for many structure applications because of their improved mechanical properties in comparison with their monolithic metal counterparts. Light alloys reinforced with short fibres or particles allow adapting more exactly the work piece material properties to requirements. There is an increasing trend in the automotive industry to use these materials for various components. Advanced properties of metal matrix composites are: • increased apparent limit of elasticity, stiffness, tensile and fatigue strength, • improved creep resistance and high temperature properties, • improved material damping, • increased wear resistance, • decreased thermal expansion. Metal matrix composites (MMCs) based on magnesium alloys are excellent candidates for engineering light structure materials, and have great potential in automotive, high performance defence and aerospace applications. In spite of relatively high number of papers dealing with microstructure and mechanical properties of MMCs based on Mg alloys, the deformation mechanisms and other physical properties of these materials are not known enough. It has already been shown that the reinforcing fibres and/or particles improve mechanical and creep properties of magnesium based MMCs compared to their monolithic counterparts. But also the disadvantage of higher production costs due to more complicated manufacturing processes has to be taken into account (Dieringa et al., 2005). Only the use of cheap materials both the alloy and the reinforcement – in relation to cost effective production processes for manufacturing of magnesium based MMCs can introduce this class of low density materials into the market. The objective of this chapter – following from this fact – is to reveal influence of various reinforcement types on the mechanical and physical behaviour of composites in which various magnesium alloys were reinforced with short alumina (Saffil®) fibres and/or SiC and Si particles. Different routs for magnesium based MMCs preparation were used: i. Squeeze casting – the melt is infiltrated into the prefabricated perform (fibres and/or particles with some binder). The preform is preheated to 800−1000 °C in order to avoid