FABRICATION AND CHARACTERIZATION OF NIOBIUM-ALUMINUM COMPOSITES: EFFECT OF SINTERING TEMPERATURE

摘要

Objectives of this research were to measure the distribution of Nb particles in the Al matrix, (density ratio 8.6:2.7) to define the effect that sintering temperature, 390 and 550℃, had on the consolidation of the composites, and the influence on the density of the mechanical properties: hardness, elastic strength, elastic modulus, ductility, and impact toughness. Specimens, 3, 5 and 7 % wt of nanometric particles of Nb, the rest 100 meshes particles of Al, were prepared by a P/M technique. Nb - Al powders were mixed in a mill for 12 h, using a 6 mm balls load of ZrO_2, the ratio in wt ZrO_2 balls/composite powder was 10:1. The powders were transferred to a die to make cylindrical specimens, applying a pressure of 3.75 MPa, the specimens were sintered either at 390 or 550℃ for 3 h, within a N2 atmosphere. Mechanical properties do not show an reinforcement effect due to Nb presence, while Vickers hardness is about 10 points higher for composites, elastic strength decreases 10 points gradually for composites, the highest value correspond to 3 % Nb composite, Al has a hardness slightly higher than the composite with 7 % Nb. Scanning microscopy showed an homogeneous Nb particles distribution for samples sintered at 550℃, homogeneity decreased for samples sintered at 390℃.