Abstract
Composite materials based on MgLi and MgY matrices reinforced with unidirectional T300 carbon fibres (45 vol.%) have been prepared by gas pressure infiltration technique. Nominal Li and Y alloying of Mg matrix were 0.5, 2, and 4 wt.% Li and 7, 13, and 20 wt.% Y, respectively. Back-scattered electron (BSE) observations and electron dispersive X-ray (EDX) analysis have revealed that penetration of lithium and formation of lithium carbide Li₂C₂ inside carbon fibres took place. Bending tests have shown that low Li alloying of Mg matrix (0.5 and 2 wt.% Li) has a favourable effect on the strength of MgLi/T300 composites. Higher Li content (4 wt.% Li) brings a much lower composite strengthening presumably due to degradation of carbon fibres with Li₂C₂. A negative effect of high yttrium alloying on the strength of MgY/T300 composites is explained by poor adherence of YC₂ interfacial layer to carbon fibres.

Key words
magnesium matrix, magnesium composites, magnesium-lithium matrix, magnesium-lithium composites, magnesium-yttrium matrix, magnesiumyttrium composites, lithium carbide, yttrium carbide, reactive wetting

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