Effect of Temperature on Low-Cycle Fatigue, Deformation and Fracture Behaviour of Superalloy Inconel 625
摘要
Low-cycle fatigue tests were conducted on superalloy Inconel 625 in the solution-treated condition in air, at different temperatures under fully reversed axial strain-controlled mode at strain rate of 5 × 10–3 s−1. Fatigue life was reduced with increase in strain amplitude and temperature. Initial cyclic hardening was observed till peak stress level, followed by softening till fracture. The sudden drop in stress amplitude at 500 °C can be associated to the dynamic strain ageing, also inferred from the serrations present in the cyclic stress–strain hysteresis loops at 500 °C and 700 °C. The fatigue life variation with plastic strain amplitude complies well with the Coffin–Mansion relationship. Deformation substructure showed evidence of dislocation bands, loops, bowing and persistent slip bands at 700 °C. Fractographs of fractured samples depict striations, typical of fatigue fracture. Increase in striation width was noticed with rise in temperature.