Structural- and mechanical-properties of hot-pressed surface modified TixSi100−x (x = 62.5 and 85 at.%) powders synthesized by mechanical alloying

In this paper, we are describing a new procedure for the synthesis of metallic- and intermetallic-matrix composites from powders obtained by mechanical alloying, subsequently coated by magnetron sputtering and compacted by hot isostatic pressing. Mixtures of Ti62.5Si37.5 and Ti85Si15 (numbers indicate at.%) were mechanically-alloyed from elemental titanium and silicon powders in a planetary ball-mill for 50 h and subsequently coated with a titanium thin film. The presence of a metallic layer on the surface of the powders affects the mechanical properties of the hot-compacted samples. The Ti thin film increases the Young modulus and fracture-toughness of the Ti85Si15 samples; this effect is not seen in the Ti62.5Si37.5 alloy. Hardness is not significantly affected. In the case of the Ti62.5Si37.5 alloy, partial oxidation of the coating was observed during the synthesis procedure; this procedure is responsible for the increase in hardness, in the Young's modulus and in the decrease in fracture-toughness.