Prediction Charpy impact energy of bcc and fcc functionally graded steels in crack divider configuration by strain gradient plasticity theory

In the present study, the Charpy impact energy of bcc ferritic and fcc austenitic functionally graded steels produced by electroslag remelting process has been investigated. To produce functionally graded steels, an electrode consists of two different spot welded slices from plain carbon and austenitic stainless steels were utilized. Functionally graded steel containing graded layers of ferrite or austenite may be fabricated via diffusion of alloying elements during remelting stage. Charpy impact energy of the specimens has been obtained experimentally in crack divider configuration and modeled with mechanism-based strain gradient plasticity theory. In this regard, the density of the statistically stored dislocations and that of geometrically necessary dislocations was related to the Vickers hardness of each layer. Afterwards, the predicted Vickers hardness of each layer was related to its Charpy impact energy. Finally, Charpy impact energy of each specimen was calculated by using the rule of mixtures. The predicted Charpy impact energies are in good agreement with those obtained from the experiments.