Structure Transformations in Multicomponent Amorphous Alloys in Connection with Grain-Boundary Segregations and Temper Embrittlement of Steels

Investigation of glass-forming alloys on the base of Fe–P system with additions of C, Mn, Cr, Si, and Ni with compositions modeling segregations on grain boundaries in steels revealed the existence of a metastable phase that precipitates at the initial stages of devitrification. This crystalline tetrahedrally close-packed phase of α–Mn structure type (χ-phase) and its aperiodic modification (cubic quasicrystal) contain less phosphorus than the known stable and metastable phosphides. Positions of P and C atoms in the unit cell of the χ-phase lattice have been established. The necessary condition for precipitation of the quasicrystalline phase is the presence of carbon. Additions of Mn + Si, Mn, or Cr promote both formation of the χ-phase and formation of the quasicrystal, their influence decreasing in this order. Composition dependences of liability to formation of the quasicrystalline structures in the model alloys agree with the data on the impact of alloying elements on the temper embrittlement of steels.