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• A Ti-based reinforced Ti 2 Ni/Ti 2 S coating was fabricated by laser cladding on TC4 alloy. • The thermodynamic characteristics of the laser molten pool were described. • The orientation relationships of β-Ti and TiC were determined. • The microhardness and wear resistance of the deposited coating were improved. In this study, a Ti 2 Ni/Ti 2 S reinforced Ti-based composite coating was fabricated using laser cladding to improve the mechanical properties of TC4 alloy. The results show that the high temperature (>3000 K) of the molten pool ensures the effectiveness of the deposited coating and the thermodynamic conditions for in situ reactions. The phases consisted of β-Ti, Ti 2 Ni, Ti 2 S, TiC, and WC. Furthermore, β-Ti nucleated and grew with TiC as heterogeneous cores due to their orientation relationships of β-Ti{1 0 0}//TiC{1 1 0} and β-Ti{1 1 0}//TiC{1 1 1}. As a result, the microhardness of the coating was 2.30 times higher than the substrate, and the wear volume decreased by 20.23 % compared to the substrate. [ABSTRACT FROM AUTHOR]

• The atomic structure of silicon irradiated by femtosecond laser was characterized. • The laser irradiated silicon region consists of a dislocation layer. • The existence of the dislocation layer enhances the nano-hardness of silicon. In this work, a one-step fs laser-induced monocrystalline silicon (Si) structure was fabricated to improve the nano-hardness properties. According to the atomic structure, three layers were found in the irradiated Si structure, namely, the amorphous Si (a-Si) layer, dislocation layer, and Si crystal layer. The a-Si layer on the surface layer was attributed to the re-solidification of melting Si material, while the dislocation layer between the a-Si and Si crystal layers contained numerous dislocations and lattice distortions, which positively affected the nano-hardness of the irradiated Si structure. The Si crystal layer was not affected by laser irradiation and maintained the initial atomic structure. This work provides a new perspective on the phase transition and microstructure study of fs laser-induced structures. [ABSTRACT FROM AUTHOR]