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

Abstract

The characteristics of hot deformation of hot extruded B2 type iron aluminide alloy powders produced by gas-atomization and water-atomization techniques have been studied using compression tests in the temperature range 850–1150°C and true strain rate range 0.001–100 s⁻¹. At strain rates higher than about 1 s⁻¹, the materials exhibited flow softening type of stress–strain curves, while at lower strain rates, the flow curves were of steady-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 material revealed that dynamic recrystallization occurs in wide ranges of temperature and strain rate with its optimum at 1075°C and 0.1 s⁻¹. However, in the case of water-atomized material, the features in the processing 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.