ABSTRACT
Manufacturing of Saffil/MgLi metal matrix composites by the melt infiltration process is accompanied by extensive interfacial redox reaction between delta-Al(2)O(3) fibers (Saffil) and lithium. The present paper deals with the Fourier transform infrared spectroscopy examination of Saffil fibers isolated from Mg-8 wt% Li alloy by the bromine/methylacetate agent focusing on the insertion of Li(+) ions into delta-Al(2)O(3) and their influence on water adsorption. Insertion of Li(+) into delta-Al(2)O(3) is monitored by gradual change of Al-O stretching bands (400-900 cm(-1)) towards more simple patterns of a spinel-like product assigned as delta(Li) which transforms to LiAl(5)O(8) during subsequent annealing. Rapid increase in the water adsorption with increase in Li content, indicated by the changes in H-O-H bending (about 1,650 cm(-1)) and O-H stretching (about 3,500 cm(-1)), is connected with the ionicity of the delta(Li) phase, which attracts polar water molecules.
ABSTRACT
Principal component analysis and cluster analysis have been used in AES investigations of fibre-matrix interactions in alumina fibre reinforced MgLi-alloys prepared by high-pressure infiltration. The samples have been fractured in ultra high vacuum to expose surfaces and interfaces without contamination. All main components exhibit Auger valence band transitions which change their shape with the chemical state. Chemometric methods have been utilized to identify characteristic peak shapes and to classify the investigated areas by composition. Fibre fracture surfaces are characterized by Al, magnesia and Li oxide formed by a redox reaction of alumina with Mg and Li penetrating along grain boundaries. For samples with high silica content a thin interfacial oxide layer on matrix grain boundaries and matrix-fibre interfaces has been found.