High-entropy alloys can either be defined as solid solution alloys containing at least five elements in equiatomic or near-equiatomic composition, or as alloys with high configurational entropies (larger than 1.5R), regardless of the number of elements involved. The present study reports on an alloy design route for refractory high-entropy alloys based on equiatomic Mo-Nb-V alloys with additions of W and Ti. In general, the work was motivated by Senkov et al. The aim of the experiments carried out was to produce a refractory high-entropy alloy with a single-phase structure. For this purpose, a systematic alloy design involving four- and five-element compositions was used. Scanning electron microscopy analysis has shown that Mo-Nb-V-xW-yTi (x = 0, 20; y = 5, 10, 15, 20, 25) is in fact a refractory high-entropy alloy with a body-centered cubic dendritic structure. Furthermore, the Ti-concentration of the experimental alloys was varied, to obtain the influence of Titanium on the microstructure development. Additionally, compressive tests at room temperature were carried out to evaluate the influence of the different alloying elements and the Ti-fraction on the mechanical properties. The observations of the present work are then compared to the published results on similar alloys from the working group of Yao et al. and critically discussed.
In the present manuscript, we report on the properties of an equiatomic Ta-Nb-Ti alloy as the basis for a novel, biomedical, multi-component alloy development. The alloy was produced using an arc melting furnace under Ar atmosphere, metallographically prepared, and investigated respectively. Furthermore, the alloy produced, as well as samples of elemental Ta, Nb, alloy Co-28Cr-6Mo, and alloy Ti-6Al-4V, were prepared with defined 1200 grit SiC grinding paper. The topography of the surfaces was evaluated using confocal microscopy and contact angle measurements subsequently. Afterwards, the biocompatibility of the novel alloy Ta-Nb-Ti was evaluated by means of cell (osteoblast) attachment as well as monocyte inflammatory response analysis. First results indicate competitive osteoblast attachment, as well as comparable expressions of fibrosis markers in comparison to conventionally used biomedical materials. In addition, the Ta-Nb-Ti alloy showed a markedly reduced inflammatory capacity, indicating a high potential for use as a prospective biomedical material.
The present study reports on the microstructural evolution and room temperature plasticity of V(-Si)-B alloys with respect to the V solid solution (VSS)-V3B2 phase region. To investigate the occurring effects systematically, different binary V-B and ternary V-Si-B alloys were produced by conventional arc melting. Scanning electron microscope (SEM) analyses and X-ray diffraction (XRD) measurements were used to characterize the resulting as-cast microstructures. For the first time, the eutectic composition was systematically traced from the binary V-B domain to the ternary V-Si-B system. The observations discover that the binary eutectic trough (VSS-V3B2) seems to reach into the ternary system up to an alloy composition of V-5Si-9B. Room temperature compression tests were carried out in order to study the impact of single-phase and multi-phase microstructures on the strength and plasticity of binary and ternary alloys. The results indicate that the VSS phase controls the plastic deformability in the VSS-V3B2 eutectic microstructure whereas the intermetallic V3B2 acts as a strong hardening phase.
Subject of the present work are principle studies on V-Si and V-B alloys with hypo-and hypereutectic compositions, regarding the effects of primary phase solidification and the formation of binary microstructures on the resulting mechanical properties. For this purpose, button shaped samples were produced by arc-melting, metallographically prepared and analyzed by scanning electron microscopy. Furthermore, room temperature compression tests have been carried out and the resulting deformations were subsequently analyzed by using electron backscatter diffraction. As a conclusion, the materials’ failure behavior was characterized and discussed with respect to the developed microstructure. The main goal of the experiments conducted is to critically discuss previously published works on the V-Si and V-B alloying systems and to obtain more profound insights on microstructure-property relations with respect to the strengthening effects and plastic deformability.
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