Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy

Abstract

High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.

The Effect of Processing Route on Properties of HfNbTaTiZr High Entropy Alloy

“…Other specimens were damaged by crack formation during deformation at room temperature or even at higher temperature (swaging at 950 °C). It should be pointed out that the possibility of hot deformation of the alloy with increased oxygen content cannot be excluded under suitable conditions (i.e., low strain rate, or higher processing temperature) [41], but this possibility needs more detailed study.…”

Tensile creep behavior of HfNbTaTiZr refractory high entropy alloy at elevated temperatures

“…The sample of HfNbTaTiZr processed by OFZ furnace had an average grain size of 1.2 ± 0.4 mm, Fig. 2(a) and 2(b), and this was substantially coarser than the grain sizes of this RHEA reported in previous works fabricated by arc-melting (140 μm) [54], spark plasma sintering (20-190 μm) [59,60], and hot isostatic pressing (100-200 μm) [29,30]. The microstructure of the sample exhibited a BCC single phase with a lattice parameter of 340 pm, Fig.…”

Research Progress of Titanium-Based High Entropy Alloy: Methods, Properties, and Applications

“…Then, the bulk HEA is prepared through the steps of ball milling/mixing, pressing, sintering, and subsequent processing. Compared with the casting method, PM application can effectively decrease the segregation of alloy components, also it can eliminate the coarse and uneven metal casting structures and significantly improve the optimum raw material consumption ( Málek et al, 2019a ). However, there are limited studies on the preparation of HEAs by powder metallurgy, at present.…”

“…In addition to traditional mechanical processing methods, there are more and more researches and applications of powder metallurgy technology in biomedical metals. According to the recently reported studies about titanium-based HEA alloys, Ti-Nb-Zr, Ti-Mo-Nb, Ti-Nb-Ag, Ti-Nb-Ta-Zr, Ti-Nb-Ta-Mn, Ti-Nb-Ta-V, Ti-Al-Ni-Co-Fe, and Ti-Nb-Hf-Zr-Ta systems ( Sakaguchi et al, 2005 ; Gabriel et al, 2012 ; Wen et al, 2014 ; Hussein et al, 2015 ; Nazari et al, 2015 ; Aguilar et al, 2016 ; Anand Sekhar et al, 2019 ; Guo et al, 2019 ; Málek et al, 2019a , b ) were prepared by PM. Wen et al (2014) conducted a comparative analysis of Ti-Nb-Ag alloy after vacuum sintering and spark plasma sintering.…”