High Temperature Deformation Behaviour and Dislocation Substructure of Impacted Inconel 625 Alloy

The dynamic impact response and dislocation characteristics of Inconel 625 alloy are investigated under strain rates ranging from 3700 to 6400 s(-1) and temperatures of 25 degrees C, 300 degrees C and 750 degrees C, respectively, using a compressive split-Hopkinson pressure bar. The results show that the flow response is sensitive to both the temperature and the strain rate. For a constant temperature, the yield strength, material constant and work hardening coefficient all increase with increasing strain rate. However, for a constant strain rate, the yield strength, material constant and work hardening coefficient all reduce with increasing temperature. The flow stress corresponding to a true strain of 0.35 can be described by a power law relation with an activation energy of 2.04 kJ/mol and an average strain rate sensitivity of 0.61. Moreover, the stress and temperature dependence of the strain rate is adequately described by the Zener-Hollomon parameter. Transmission electron microscopy (TEM) observations show that the dislocation density increases with increasing strain rate, but decreases with increasing temperature. The dislocation density and work hardening stress are related by the Bailey- Hirsch equation sigma=sigma(0) + alpha(1)Gb root rho, with alpha(1) equal to 0.316.