HfTiZrSc is a novel hexagonal close-packed refractory high entropy alloys, addition of Al as typical additives significantly enhances the strength and ductility. To reveal the effect of Al addition on thermal properties, we combine the EMTO-CPA ab initio calculations with quasi-harmonic Debye-Grüneisen model to studied the thermodynamic properties of the Hf_0.25Ti_0.25Zr_0.25Sc_0.25-xAl_x (x ≤ 15 at.%) HEAs. With Al substitution for Sc, the strength of Hf_0.25Ti_0.25Zr_0.25Sc_0.25-xAl_x (x ≤ 15 at.%) is enhanced significantly, despite essentially similar thermal softening trend. Thermal expansion coefficient of Hf_0.25Ti_0.25Zr_0.25Sc_0.25-xAl_x increase with increasing Al content. Thermodynamic entropy of Hf_0.25Ti_0.25Zr_0.25Sc_0.25-xAl_x (x ≤ 15 at.%) increases dramatically with temperature, the trend is to some degree suppressed with increase of Al content, which is discussed from vibrational, electronic and configuration entropy contribution. The influences of Al content on Debye-temperature and Grüneisen parameter are also further studied. The present investigation is valuable for optimal designing of overall performance of Hf_0.25Ti_0.25Zr_0.25Sc_0.25-xAl_x alloys.

HfTiZrSc是一种新型的六角形密堆积耐火高熵合金，添加Al作为典型添加剂可显着提高强度和延展性。为了揭示Al对热性能的影响，我们将EMTO-CPA从头算术与准谐波Debye-Grüneisen模型相结合，以研究Hf _0.25 Ti _0.25 Zr _0.25 Sc _0.25-x Al _x（x≤ 15 at。％）HEA。用Al代替Sc时，Hf _0.25 Ti _0.25 Zr _0.25 Sc _0.25-x Al _x的强度尽管热软化趋势基本相似，但（x≤15 at。％）仍显着提高。Hf _0.25 Ti _0.25 Zr _0.25 Sc _0.25-x Al _x的热膨胀系数随着Al含量的增加而增加。Hf _0.25 Ti _0.25 Zr _0.25 Sc _0.25-x Al _x的热力学熵（x≤15 at。％）随温度急剧增加，这种趋势在一定程度上随Al含量的增加而受到抑制，这是从振动，电子和组态熵的贡献来讨论的。还进一步研究了铝含量对德拜温度和Grüneisen参数的影响。本研究对于Hf _0.25 Ti _0.25 Zr _0.25 Sc _0.25-x Al _x合金整体性能的最佳设计是有价值的。