Effect of mechanical alloying on microstructure and mechanical properties of hot-pressed Nb-16Si alloys

Nb-16 at.% Si bulk alloys were fabricated by hot pressing from compound powders milled for different times. The influences of mechanical alloying on microstructure and mechanical properties of the hot-pressed alloys were investigated. The results indicate that the particle size of powders was significantly refined and the addition of absolute ethyl alcohol suppressed the agglomeration of powders. When milling time increased from 6 to 24 h, the constituent phases (Nbss, Nb5Si3 and Nb3Si) changed from large size trips to fine near-equiaxed shape, and the volume fraction of ductile Nbss decreased. In addition, Vickers hardness and flexural strength of bulk alloys increased gradually owing to the enhancement of the volume fraction of niobium silicides. Fracture toughness was in range of 10.98-13.23 MPa m(1/2), which was higher than that of cast materials. It was attributed to the positive role of ductile phase and fine-grain toughening. (C) 2010 Elsevier B.V. All rights reserved.