Metastable phase formation in Fe–Si system using non-equilibrium techniques

Metastable alloy phase formation in Fe/Si system with nominal composition Fe50Si50 using the techniques of mechanical alloying (MA), solid state interdiffusion (SSI) and swift heavy ion (SHI) irradiation has been compared. The products of SSI depend upon the structure of the iron layers. In the multilayer with amorphous iron layer, the product of SSI is crystalline FeSi phase, while in the multilayer with crystalline iron layer the product is an amorphous phase. MA results in the formation of metastable BCC phase with extended solid solubility. Results of both MA and SSI can be understood in terms of a model in which an asymmetry in the diffusivities of the two constituents is a necessary condition for amorphisation to occur during solid state reaction. Amorphisation during SHI irradiation can be understood in terms of a thermal spike model.