Grain Refinement and Improvement in Mechanical Properties of Nb-Al-Si Intermetallic Alloys

Abstract

Nb–Al–Si intermetallic alloys having submicron crystal grains have been produced using the self-propagating high-temperature synthesis (SHS, or combustion synthesis) method followed by the bead milling technique and the spark plasma sintering (SPS) method. The intermetallic alloys were combustion-synthesized from elemental powders of niobium, aluminum and silicon, and then ball-milled and bead-milled to reduce the alloy powder particle size. The milled alloy powder was consolidated using the SPS method with a sintering time of 300 s at a sintering temperature of 1 373 K. The increase in milling time reduced the grain size of the sintered alloy. Particularly, the grain size was dramatically reduced when zirconia beads of a 0.2-mm diameter were used after milling with zirconia balls of a 10-mm diameter. The Vickers hardness, bending strength and fracture toughness of the sintered alloys increased with the decrease in grain size.