Tuning phase stability and short-range order through Al doping in (CoCrFeMn)100−xAlx high-entropy alloys

For<math><mrow><msub><mrow><mo>(</mo><mi>CoCrFeMn</mi><mo>)</mo></mrow><mrow><mn>100</mn><mo>-</mo><mi>x</mi></mrow></msub><mi mathvariant='normal'>A</mi><msub><mi mathvariant='normal'>l</mi><mi>x</mi></msub></mrow></math> high-entropy alloys, we report on the phase evolution with increasing Al content ( 0 ≤ x ≤ 20 at.%). From first-principles theory, aluminum doping drives the alloy structurally from fcc to bcc separated by a narrow two-phase region (fcc+bcc), which is well supported by our experiments. Using KKR-CPA electronic-structure calculations, we highlight the effect of Al doping on the formation enthalpy (alloy stability) and electronic dispersion of <math><mrow><msub><mrow><mo>(</mo><mi>CoCrFeMn</mi><mo>)</mo></mrow><mrow><mn>100</mn><mo>-</mo><mi>x</mi></mrow></msub><mi mathvariant='normal'>A</mi><msub><mi mathvariant='normal'>l</mi><mi>x</mi></msub></mrow></math> alloys. As chemical short-range order indicates the nascent local order, and entropy changes, as well as expected low-temperature ordering behavior, we use KKR-CPA-based thermodynamic linear response to predict the chemical ordering behavior of arbitrary complex solid-solution alloys—an ideal approach for predictive design of high-entropy alloys. The predictions confirm our present experimental findings and other reported ones.