Alloys with a hexagonal close-packed (HCP) lattice often suffer from intrinsic brittleness due to their insufficient number of slip systems, which limits their practical uses. In this paper, nevertheless, we show that remarkably tensile ductility in HCP Hf-Zr-Ti medium entropy alloys (MEAs) was achieved, particularly in the MEAs with a higher content of Hf. Both first-principles calculation and experimental analyses reveal that addition of Hf increases basal I2 stacking fault energy and decreases prismatic stacking fault energy in these HCP MEAs, which promotes the source of pyramidal dislocations due to the facilitated cross slips of basal dislocations and eventually give rise to the observed large tensile ductility. Our current findings not only shed new insights into understanding deformation of HCP alloys, but also provide a basis for controlling alloying effects for developing novel HCP complex alloys with optimized properties.

具有六方密排 (HCP) 晶格的合金由于滑移系统数量不足而经常遭受内在脆性，这限制了它们的实际应用。然而，在本文中，我们表明在 HCP Hf-Zr-Ti 中熵合金 (MEA) 中实现了显着的拉伸延展性，特别是在 Hf 含量较高的 MEA 中。第一性原理计算和实验分析均表明，Hf的添加增加了这些HCP MEA中的基础I2层错能并降低了棱柱形层错能，由于促进了基面位错的交叉滑移，从而促进了锥体位错的来源并最终产生到观察到的大的拉伸延展性。我们目前的发现不仅为理解 HCP 合金的变形提供了新的见解，