Influence of temperature and strain rate on the flow stress of an FeAl alloy

Abstract

The deformation behavior of an FeAl alloy processed by hot extrusion of water atomized powder has been investigated. Compression tests are performed in the temperature range 1073-1423 K and in the strain rate range 0.001-100 s⁻¹ up to a true plastic strain of 0.5. The flow stress has been found to be strongly dependent on temperature as well as strain rate. The stress exponent in the power law rate equation is estimated to be in the range 7.0–4.0, decreasing with temperature. The activation energy for plastic flow in the range 1073-1373 K varies from 430 kJ mol⁻¹ at low stresses to 340 kJ mol⁻¹ at high stresses. However, it is fairly independent of strain rate and strain. The activation area has similarly shown a stress dependence and lies in the range 160–45b². At 1423 K and at strain rates lower than 0.1 s⁻¹ a strain rate sensitivity of 0.3 is observed with an associated activation energy of 375 kJ mol⁻¹. The plastic flow in the entire range of temperature and strain rate investigated appears to be controlled by a diffusion mechanism. The results have revealed that it is possible to process the alloy by superplastic forming in the range 1373–1423 K at strain rates lower than 0.1 s⁻¹.