New (FeCoCrNi)-(B,Si) high-entropy metallic glasses, study of the crystallization processes by X-ray diffraction and Mossbauer spectroscopy

The role of B and Si in the formation of (FeCoCrNi)(100-x-y)BxSiy high-entropy metallic glasses is studied. It is found that a content of B between 10 and 20 at% and of Si between 5 and 15 at% is able to produce a completely amorphous structure. The microstructural evolution of two of this high-entropy metallic glass compositions, (FeCoCrNi)(80)B-20 and (FeCoCrNi)(80)B10Si10, have been studied by X-ray diffraction and Transmission Mossbauer Spectroscopy. In both compositions, the first crystallization process corresponds to the formation of metastable, M3B, and stable, M-2(B,Si), borides where M stands for metallic atoms. In the Si containing sample a BCC phase also appears. At the second crystallization stage the metastable and the BCC phases disappear and stable M2B or M-2(B,Si) phases begin to grow simultaneously with an FCC structure that presents a distribution of possible environs. The fully crystallized structure consists of boride and silicide phases and a paramagnetic FCC phase. The presence of Si promotes the crystallization of a BCC phase and the refinement of the microstructure leading to smaller and more uniform grains.