EFFECT OF TITANIUM ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MECHANICALLY ALLOYED Nb-Ti-Al ALLOYS

摘要

The goal of this work was to analyse the influence of titanium on microstructure and mechanical properties of mechanically alloyed Nb-Ti-Al alloys. Two alloys composition: Nbl5Til5Al and Nb22Til5Al (all in at. percent) were chosen. The X-ray diffraction of both milling alloys showed that 100 h of mechanical alloying produces the niobium solid solution phase (Nb_(ss)). Powders after 100 h of mechanical alloying subjected annealing at 1000 deg C were composed of Nb_(ss) and the Nb_3Al intermetallic phase. The alloy with 15 percent Ti after consolidation was composed mainly of three phases: Nb_(ss), Nb_3Al and dispersoid, while the alloy with 22 percent Ti contained additionally very brittle and unfavourable Nb_2Al intermetallic phase. The presence of the detrimental Nb_2Al phase lowers considerably the hardness of the produced alloy. Relatively low fracture toughness of both alloys suggests that the incorporation of a ductile phase (Nb_(ss)) into microstructure is not sufficient for improving the ductility of the synthesized alloys.