Field-activated pressure-assisted synthesis of NiTi

The synthesis of dense NiTi starting from elemental powders was investigated utilizing the field-activated, pressure-assisted technique. The effect of current intensity, time, and reactant particle size on the characteristics of the product was investigated. Reaction between Ni and Ti did not result in the complete conversion to the desired single-phase product (NiTi). The product contained NiTi2, Ni3Ti, and the metastable phase Ni4Ti3. However, the number and the amounts of these secondary phases were significantly reduced with an increase in the applied current and synthesis time, or the use of smaller reactant particle sizes. A high degree of conversion was achieved in a relatively short time (20 min), with a current in the range of about 1300-1500 A (4585-5290 kA/m(2)). Under these conditions, the dense product (99% relative density) contained NiTi as the major phase with small amounts (5.7-7.8 mol%) of NiTi2. (C) 2003 Elsevier Science Ltd. All rights reserved.