Deformation behavior of Inconel 690 super alloy evaluated by impact test

The dynamic impact deformation behavior, fracture characteristics and microstructural evolution of Inconel 690 alloy under high rate loading conditions are studied. Mechanical impact tests are performed at strain rates ranging from 2.3×103 to 8.3×103 s−1 at room temperature by compressive split-Hopkinson bar. The effects of strain rate on dynamic flow response, work hardening characteristics, strain rate sensitivity and thermal activation volume are evaluated. A constitutive law is proposed, based on the Zerilli–Armstrong model. Evolutions of dislocation and twins substructures are investigated using transmission electron microscopy. Relationships between flow stress, dislocation and twinning are analyzed and discussed in terms of loading conditions. Scanning electron microscopy is used to evaluate damage initiation and fracture mechanisms. The observed flow stress–strain response is influenced greatly by strain rate, resulting in obvious change of work hardening rate, strain rate sensitivity, activation volume, and also dislocation tangle and deformation twin substructures. Catastrophic failure at high rate results from the formation of localized shear bands. The proposed constitutive law describes the observed response quite well.