Metal Matrix Composites (MMCs) as high performance metallic material

 
Metal matrix composites (MMCs) have developed during the last decade and some of them could be used for structural applications – potentially boosting the performances by 50% or more compared with pristine metallic solutions. Developing MMCs is challenging as it requires excursions at high temperature where undesirable chemistry / stresses generation can be initiated.

Objectives
The main objective of the study was to investigate few materials showing, on paper, good performances. Mg-8%Li reinforced with carbon fibres, Ti6Al4V reinforced with TiB and Mg (AZ91) reinforced with alumina nano particles.

Achievements
In Mg-Li matrix composite, Li diffuses very quickly in the carbon fibres inducing swelling and Lithium carbide formation – more work would be needed to have reinforcement compatible with Li, this later providing very interesting properties to Mg when added in large enough quantity (8%). In Mg reinforced with nanoparticles, particle distribution remains unsatisfactory, the mixing proved challenging. As back up, micro-size particles were used and processing developed. In Ti6Al4V, TiB has been swapped for TiC with lower vol%. The composites passed the SCC test opening the door to structural applications.

Benefits
The Ti64V based composite is a candidate for high performance applications. Activity conducted with unofficial sub-contractor: Slovak academy of Science which worked on Mg-Li matrix composite - allowing this institute to understand the space industry requirements.