Influence of Molybdenum on the Microstructure, Mechanical Properties and Corrosion Resistance of Ti20Ta20Nb20(ZrHf)20−xMox (Where: x = 0, 5, 10, 15, 20) High Entropy Alloys

Abstract

The presented work was focused on investigating the influence of the (hafnium and zirconium)/molybdenum ratio on the microstructure and properties of Ti20Ta20Nb20(ZrHf)20−xMox (where: x = 0, 5, 10, 15, 20 at.%) high entropy alloys in an as-cast state. The designed chemical composition was chosen due to possible future biomedical applications. Materials were obtained from elemental powders by vacuum arc melting technique. Phase analysis revealed the presence of dual body-centered cubic phases. X-ray diffraction showed the decrease of lattice parameters of both phases with increasing molybdenum concentration up to 10% of molybdenum and further increase of lattice parameters. The presence of two-phase matrix microstructure and hafnium and zirconium precipitates was proved by scanning and transmission electron microscopy observation. Mechanical property measurements revealed decreased micro- and nanohardness and reduced Young’s modulus up to 10% of Mo content, and further increased up to 20% of molybdenum addition. Additionally, corrosion resistance measurements in Ringers’ solution confirmed the high biomedical ability of studied alloys due to the presence of stable oxide layers.

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“…Because the HEAs contained many elements, this resulted in substantial lattice deformation in the grain configuration. The kinetic slow diffusion effect, caused by distortion in the structural lattice of HEAs, will obstruct atom mobility [55,56]. Fe atoms visible in area C (Figure 2), but not in area E (Figure 2), indicated a tiny quantity of Fe atoms diffusing to the HEAs with a limited diffusion distance.…”

Influence of Hafnium Addition on the Microstructure, Microhardness and Corrosion Resistance of Ti20Ta20Nb20(ZrMo)20−xHfx (where x = 0, 5, 10, 15 and 20 at.%) High Entropy Alloys

“…For all studied HEAs, the refinement of lattice parameters lead to an increase in unit cell parameters with increasing Hf concentration. The increase in lattice parameters by Hf addition could be correlated with the high atomic radii of pure Hf (r i = 1.578 Å [ 29 ]) which contributes to the expansion of the unit cell. Additionally, the changes in lattice parameters with an increase in Hf content are shown in Table 2 and presented graphically in Figure 2 .…”

“…Our previous work presents the description of the aforementioned thermodynamical parameters calculations. The physical and chemical properties of all alloying elements in the studied materials have also been described [ 28 , 29 ]. The calculated thermodynamical parameters for all studied Hf-containing HEAs are collected in Table 1 .…”

Evaluation of Microstructure and Mechanical Properties of a Ti10Mo8Nb Alloy for Biomedical Applications

“…Another element that is used in biomedical applications is molybdenum. It was widely investigated for biomedical application because it has appropriate mechanical properties and biocompatibility, as well as being a strong stabilizer of β-phase for concentrations higher than 10% [19][20][21][22].…”