The equimolar NbTaTiZr refractory high-entropy alloy (RHEA) exhibits outstanding softening resistance at elevated temperatures as a result of its high phase stability and high melting point. Interestingly, the biocompatibility of this material is also comparable to that of pure Ti, and have great potential to be utilized as biomedical components [1,2]. Due to its high melting point and strong affinity with oxygen, the pulverization of RHEAs remains difficult and uneconomical using conventional rotating electrode pulverization and melt atomization routes [3-5], which impedes the application of this material in powder metallurgy and additive manufacturing technologies.

It is well known that hydrogen atoms preferentially segregate to grain boundaries in alloys and subsequently react to form metal hydrides. This process leads to a phenomenon known as hydrogen embrittlement and the fracture of the material initiated from grain boundaries [6-8]. The small radius of the hydrogen atom also allows this process to occur in BCC HEAs as hydrogen atoms diffuse into the materials and occupy both tetrahedral vacancies in the BCC structure and defects [9, 10]. In this work, we found that hydrogen absorption can embrittle the NbTaTiZr RHEA and promote intragranular fracture due to segregation of hydrogen atoms at grain boundaries. Synergistic effects of the hydrogenation temperature and time on the pulverization behavior of the NbTaTiZr RHEA were investigated, and the relation between grain sizes in the original ingots and particle sizes in the pulverized powders was explored. Then spherical powders in purpose to additive manufacturing can be obtained finally by further plasma spheroidization. The present findings not only provide a highly efficient approach to produce high-quality powders of alloys with high-melting points, but also shed light into understanding hydrogen embrittlement of RHEAs.

References

[1] Y. Yuan; Y. Wu; Z. Yang; X. Liang; Z. Lei; H. Huang; H. Wang; X. J. Liu; K. An; W. Wu; Z. P. Lu. Materials Research Letter; 2019; 7; 225-231.

[2] M. Todai; T. Nagase; T. Hori; A. Matsugaki; A. Sekita; T. Nakano. Scripta Materialia, 2017, 129, 65-68.

[3] G. Chen; S. Y. Zhao; P. Tan; J. Wang; C. S. Xiang; H. P. Tang. Powder Technology, 2018, 333, 38-46.

[4] F. Lukac M. Dudr; R. Musalek; J. Klecka; J. Cinert; J. Cizek; T. Chraska; J. Cizek; O. Melikhova; J. Kuriplach; J. Zyka; J. Malek. Journal of Materials Research, 2018, 33, 3247-3257.

[5] T. Ishimoto; R. Ozasa; K. Nakano; M. Weinmann; C. Schnitter; M. Stenzel; A. Matsugaki; T. Nagase; T. Matsuzaka; M. Todai; H. S. Kim; T. Nakano. Scripta Materialia, 2021, 194, 113658.

[6] X. Li; X. Ma; J. Zhang; E. Akiyama; Y. Wang; X. Song. Acta Metallurgical Sinica English Letters, 2020, 33, 759-773.

[7] W. Qin; N. A. P. Kiran Kumar; J. A. Szpunar; J. Kozinsk. Acta Materialia, 2011, 59, 7010-7021.

[8] C. Zhang; Y. Yang; Y. Zhang; J. R. Liu; L. You; X. P. Song. Journal of Nuclear Materials, 2017, 493, 448-459.

[9] T. W. Na; K. B. Park; S. Y. Lee; S. M. Yang; J. W. Kang; T. W. Lee; J. M. Park; K. Park; H. K. Park. Journal of Alloys and Compounds, 2019, 817, 152757.

[10] X. Li; J. Yin; J. Zhang; Y. Wang; X. Song; Y. Zhang; X. Ren. Journal of Materials Science and Technology, 2022, 122, 20-32.