Study of Carbon Fibre-Reinforced Magnesium Composites (Introduction to interfacial phenomenon)

Composite materials are known to combine interesting properties of different materials. This research concerns magnesium alloys reinforced by carbon fibres weaves. Such a material can theoretically exhibit a yield strength/density ratio around 500 compared to ~200 for Ti6Al4V and ~125 for Al2024-T6. This composite is thought to be especially promising for aeronautics if interaction between fibres and magnesium can be controlled and optimized. The strategy studied to enhance interaction between matrix and fibres consists in covering a thin layer of carbide former metal (Zr, Ti) by PVD as a primary treatment of carbon weaves. This intermediate product can then be heated up between 300-700°C in an argon atmosphere in order to form stable carbides. The wetability of treated weaves by liquid magnesium is potentially higher because carbides are not fully covalent (partially metallic) and so they can have more interface interaction with liquid metals. Further crystal lattice parameters of particular carbides can be close to the ones of metal crystal lattices and interface energy can consequently be reduced when they form carbide-metal bonds. Furthermore magnesium is known for its high oxygen attraction and is able to reduce a lot metallic oxides. It is a key fact because liquid magnesium easy wets its oxide in certain conditions.