On the effect of Fe in L12 strengthened Al–Co–Cr–Fe–Ni–Ti complex concentrated alloy

In this study, the effect of Fe in precipitation strengthened Al-Co-Cr-Fe-Ni-Ti complex concentrated alloys (CCAs) is investigated. The amount of Fe significantly affected the γ′ morphology, microstructural stability, lattice misfit, solvus temperature and mechanical behaviour. The decrease in the Fe content from 11.5 (Al7.8Co20.6Cr12.2Fe11.5Ni40.7Ti7.2) to 0 (Al7.8Co20.6Cr12.2Ni52.2Ti7.2) at% changed the precipitate morphology from spherical to cuboidal upon 50h ageing at 900°C. Also, the lattice misfit and solvus temperature of the alloy increased from 0.097 to 0.41% and 1109 to 1199°C, respectively, with the complete removal of Fe from the alloy system. Coarsening studies at 900°C (up to 550h) revealed that the γ′ coarsening was driven by evaporation and condensation (EC) mechanism in Al7.8Co20.6Cr12.2FexNi52.2-xTi7.2 (x=11.5, 5 and 0, in at%) alloys. The coarsening rate constants (Kr) were calculated for the three alloys; among them, the alloy without Fe showed the least value (2.83 × 10−27 m3 s−1). The obtained results on the effect of Fe in L12 strengthened CCAs offer a new platform for the development of advanced high-temperature alloys. [Display omitted]