Hardening and softening in Mg-Li-Al matrix composites
Zuzanka Trojanova*, Zdenek Drozd*, Kristian Mathis*, Pavel Lukać*, Stanislav Kudela** *Charles University, Faculty Mathematics and Physics, Ke Karlovu 5, CZ - 121 16 Praha 2, Czech Republic **Institute of Materials & Machine Mechanics SAS, Račianska 75, SK - 838 12 Bratislava, Slovakia
Annals 4 No. 10, 2004 pages 127-132
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abstract Mg-xLi-yAl (x = 4, 8, 12, y = 0, 3, 5) matrix composites reinforced with short δ-alumina (Al2O3) fibres were manufactured by the pressure infiltration process. The fibrous preform was prepared using commercial alumina fibres (Saffil) via water dispersion, sedimentation and drying operations without any binder. The structure of composite materials consisted of short δ-alumina fibres (10% vol.) distributed planar-randomly within Mg-Li-Al matrix (hcp, hcp+bcc, bcc). No significant fibre damage resulting from the Mg-Li-Al melt attack was observed. Compression tests of cylindrical composite samples were carried out at temperature between 20÷200°C. The results obtained revealed that the flow stresses of the composites are substantially higher than those of unreinforced alloy. These difference decreases with increasing test temperature. Different contributions to the strength of composites were evaluated. The shear stress at fibre/matrix interface were of greatest importance in this regard, though the contribution resulting from the dislocation density increase was also significant. Key words: metal matrix composites, magnesium alloys, strain hardening, high temperature properties