High-temperature phase characterization of AlCrFeNiTi compositionally complex alloys

Abstract

In this work, alloys composed of the 5 base-elements Al, Cr, Fe, Ni and Ti and elements in minor amounts were produced by arc melting and powder metallurgy. The alloys’ phase distribution was analyzed via high energy X-ray diffraction (HEXRD), neutron diffraction and electron backscatter diffraction (EBSD). The two studied compositions have low concentrations of the elements Al and Ti, medium concentrations of the elements Cr and Fe and high amounts of Ni (chemical composition in at.-%: Al10Cr20Fe20Ni40Ti5, Al10Cr20Fe20Ni35Ti10). The goal then was to analyze the microstructure of these compositions at elevated temperatures in dependence of their chemical composition and the production method. Analysis of both compositions show the presence of B2-phases, L12-phases, Full Heusler-phases (H_L21), C14_Laves-phase and σ-phase. The combination of dilatometric tests with microstructure analysis via HEXRD and neutron diffraction gives the possibility of observing changes in phase amounts in dependence of temperature. A quantification of phase amounts in the compositions is supported by thermodynamic calculations of stable phases, applying the calculation-of-phase-diagrams (CALPHAD) method within the software Thermocalc. Due to its detrimental influence on ductility the existence of σ-phase is undesired in nickel-chromium-iron alloys and hence σ-phase precipitation with an associated dissolution of the phases B2 and L12 at elevated temperatures was studied in detail.