Lattice strain during compressive loading of AlCrFeNiTi multi-principal element alloys

Abstract

In this work, multi-principal element alloys (MPEAs) with the five base elements Al, Cr, Fe, Ni and Ti plus elements in minor amounts were produced by powder metallurgy and their microstructure and elastic behavior were analyzed via light and scanning electron microscopy, electron backscatter diffraction (EBSD) and synchrotron X-ray diffraction. The two studied compositions are an MPEA with Al, Cr, Fe, Ni and Ti in equimolar ratio as well as a similar composition with a concentration of Ti reduced to 10 mol%. The goal is to analyze the microstructural behavior of these compositions during macroscopic loading in dependence of chemical composition and phases present. Analysis via synchrotron X-ray diffraction predicts the presence of body-centered cubic phases, Full Heusler-phases and C14_Laves-phases in both compositions, MPEA5 and MPEA_Ti10. Synchrotron X-ray diffraction offers the possibility to monitor the deformation of these phases during macroscopic loading of specimens. Thermodynamic calculations of stable phases predicted a microstructure of MPEA5 consisting of body-centered cubic and Full Heusler-phases at room temperature. Further calculation and X-ray diffraction experiments showed the stabilization of minor amounts of C14_Laves-phase (Fe 2Ti) at room temperature with a decreasing amount of Ti. MPEA5 showed the development of long and un-branched cracks during compressive testing, which resulted in a remarkable decrease in lattice-dependent elastic moduli. MPEA_Ti10 exhibited branched cracks during compression tests. Also, the lattice-dependent elastic moduli of MPEA_Ti10 did not change notably during the compression tests. In both compositions, the Full Heusler-phase showed the lowest lattice-dependent elastic moduli, hence taking the largest share of the overall deformation among all phases present in the materials under macroscopic loading.