Application of strain gradient plasticity theory to model Charpy impact energy of functionally graded steels

Functionally graded ferritic and austenitic steels were produced through electroslag refining by setting the austenitic and carbon steels with appropriate thickness as electrode. Charpy impact energy of the specimen has been studied and modeled regarding the mechanism-based strain gradient plasticity theory. The yield stress of each layer was obtained by the density of the statistically stored dislocations of that layer and by assuming Holloman relation for the corresponding stress–strain curves, tensile strength of the constituent layer were determined via numerical method. Charpy impact energy of each layer was related to the corresponding area under stress–strain curve of that layer and finally by applying the rule of mixtures, Charpy impact energy of functionally graded steels was determined. The obtained results of the proposed model are in good agreement with the experimental ones.