Hot working behavior of extruded powder products of B2 iron aluminide alloys

The characteristics of hot deformation of hot extruded B2 type iron alumini de alloy powders produced by gas-atomization and water-atomization techniqu es have been studied using compression tests in the temperature range 850-1 150 degreesC and true strain rate range 0.001-100 s(-1). At strain rates hi gher than about 1 s(-1), the materials exhibited flow softening type of str ess-strain curves, while at lower strain rates, the flow curves were of ste ady-state type. The apparent activation energy for hot deformation has been evaluated and is in the range 430-465 kJ mole(-1) both in the gas-atomized and water-atomized materials. The processing map for the gas-atomized mate rial revealed that dynamic recrystallization occurs in wide ranges of tempe rature and strain rate with its optimum at 1075 degreesC and 0.1 s(-1). How ever, in the case of water-atomized material? the features in the processin g map have changed with strain. The gas-atomized material is prone to flow instabilities like flow localization at strain rates higher than 10 s(-1), while the water-atomized material exhibits stable flow even at high strains and high strain rates. (C) 2001 Elsevier Science B.V. All rights reserved.