Abstract

The HfTaTiNbZr high-entropy alloy (HEA) of equimolar concentration is fabricated from powder components by high-energy ball milling (HEBM) and spark plasma sintering (SPS). The treatment of the initial powders was performed in a planetary high-energy ball mill for 20, 40, 60, and 90 min. It is shown based on the studied surface morphology, microstructure, and phase composition of HEA samples that the multicomponent powder mixture Hf + Ta + Ti + Nb + Zr is subjected to substantial structural variations during HEBM. Starting from X-ray diffraction analysis (XRD) data, it is established that mill treatment for 20 min leads to the formation of a Hf-based solid solution with an fcc structure (Fm3m). Subsequent HEBM for 40 min promotes the formation of a Ta-based solid solution with a bcc structure (Im3m). Peaks of Hf-based and Ta-based solid solutions in the diffraction pattern completely merge after 60-min treatment, forming one common asymmetric peak in an angle range of ~35°–51°. It is revealed that the formation of the HEA with the HfTaTiNbZr composition and bcc structure is observed after 90-min HEBM. The material has a homogeneous structure according to scanning electron microscopy (SEM) data, and the results of energy-dispersive analysis showed that initial elements Hf, Ta, Ti, Nb, and Zr are uniformly distributed in the material bulk. The powders formed after 90-min HEBM are sintered at t = 1150 and 1350°C for 10 min. The results of XRD, SEM, and energy-dispersive spectrometry of SPS-consolidated high-entropy alloys at t = 1350°C show that the material preferentially consists of one phase with the bcc structure and a small amount of Hf₂Fe and ZrO. The hardness of the sintered HEA material (10.7 GPa) exceed the hardness of the material consolidated from the mixture of initial elements (6.2 GPa) by a factor 1.8. Density of the samples sintered from initial and HEA powders at t = 1350°C is 9.49 g/cm³ (95.8%) and 9.87 g/cm³ (99.7%), respectively.

中文翻译：

---

高能球磨制备高熵HfTaTiNbZr合金的结构特征

摘要

等摩尔浓度的HfTaTiNbZr高熵合金（HEA）由粉末成分通过高能球磨（HEBM）和火花等离子体烧结（SPS）制成。初始粉末的处理在行星式高能球磨机中进行20、40、60和90分钟。根据研究的HEA样品的表面形态，微观结构和相组成显示，HEBM期间，多组分粉末混合物Hf + Ta + Ti + Nb + Zr会发生较大的结构变化。从X射线衍射分析（XRD）数据开始，可以确定经过20分钟的碾磨处理会导致形成具有fcc结构（Fm 3 m）。随后的40分钟HEBM促进了具有bcc结构（Im 3 m）的Ta基固溶体的形成。经过60分钟处理后，衍射图中Hf基和Ta基固溶体的峰完全融合，在〜35°–51°的角度范围内形成一个常见的不对称峰。揭示了在90分钟的HEBM后观察到具有HfTaTiNbZr组成和bcc结构的HEA的形成。根据扫描电子显微镜（SEM）数据，该材料具有均质结构，能量分散分析的结果表明，初始元素Hf，Ta，Ti，Nb和Zr均匀分布在材料块中。90分钟HEBM之后形成的粉末在t烧结= 1150和1350°C持续10分钟。SPS固结的高熵合金在t = 1350°C的XRD，SEM和能谱分析结果表明，该材料优先由bcc结构的一相和少量的Hf ₂ Fe和ZrO组成。烧结的HEA材料的硬度（10.7 GPa）比由初始元素的混合物（6.2 GPa）固结的材料的硬度高1.8倍。在t = 1350°C时，从初始粉末和HEA粉末烧结的样品的密度分别为9.49 g / cm ³（95.8％）和9.87 g / cm ³（99.7％）。