Controllable growth of two-dimensional iron carbide in steels under accumulation deformation.

Two dimensional (2D) materials such as metal carbides are attractive owing to their unique structures and various potential applications. Although various synthetic methods have been developed for fabrication of 2D materials, it is still challenging to directly synthesize 2D carbides. Herein, we propose a new approach to convert in-situ 3D iron carbide into defect free 2D one in conventional carbon steels by controlling the deformation accumulation to drive atomic rearrangement within the carbides. Density functional theory (DFT) calculation demonstrated that ring-like, helical and other morphological 2D iron carbides can be formed under 30 % compressive deformation. Experimentally, the strength of 2D hexagonal iron carbide is estimated to be 12 GPa-18 GPa, which is 4-5 times that of original orthorhombic iron carbide (3.0 GPa-3.5 GPa) and the in-situ grown 2D carbide results in 176 % increase in strength of the steels. The first principles simulations show that the 2D iron carbides can be converted through its multiple slip systems under both the compressive and tensile pressure. This approach may open a new door for in-situ controllable growth of various 2D materials owning to rich metallic bond variety, slip system multiplicity and deformation diversity in metallic alloys.