“…At least ten readings were obtained in the HEA matrix to avoid the effect of chemical inhomogeneity in order to represent the actual hardness of xW s , and the average value was used. Figure 6(a) summarizes the influence of the chemical composition on the hardness of xW s .Figure 6( a ) Effects of the composition on the hardness of xW s , ( b ) true stress-true strain curves of xW s , ( c ) variation in the compressive yield strength and fracture strain of xW s with varying compositions and a comparison with pure tungsten (this work), TaNbWMoV and TaNbWMo 93 and ( d ) Comparison of the hardness levels of xW s with W-V (W-3.5at.%V, W-16at.%V and W-21.3at.%V) 44 , W-Re (W-2at.%Re 48 and W-24.7at.%Re-SPS at 1500 °C) 47 , W-Cr (W-30at.%Cr, W-50at.%Cr and W-70at.%Cr) 58 , W-Mo (W-32.2at.%Mo, W-45.5at.%Mo and W-56.3at.%Mo) 56 , W-Ta (W-99at.%Ta, W-96at.%Ta and W-90.7at.%Ta) 50 , and W-Ti (W-29at.%Ti, W-40.2at.%Ti and W-48.8at.%Ti) 54 .
…”
The WxTaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.
“…At least ten readings were obtained in the HEA matrix to avoid the effect of chemical inhomogeneity in order to represent the actual hardness of xW s , and the average value was used. Figure 6(a) summarizes the influence of the chemical composition on the hardness of xW s .Figure 6( a ) Effects of the composition on the hardness of xW s , ( b ) true stress-true strain curves of xW s , ( c ) variation in the compressive yield strength and fracture strain of xW s with varying compositions and a comparison with pure tungsten (this work), TaNbWMoV and TaNbWMo 93 and ( d ) Comparison of the hardness levels of xW s with W-V (W-3.5at.%V, W-16at.%V and W-21.3at.%V) 44 , W-Re (W-2at.%Re 48 and W-24.7at.%Re-SPS at 1500 °C) 47 , W-Cr (W-30at.%Cr, W-50at.%Cr and W-70at.%Cr) 58 , W-Mo (W-32.2at.%Mo, W-45.5at.%Mo and W-56.3at.%Mo) 56 , W-Ta (W-99at.%Ta, W-96at.%Ta and W-90.7at.%Ta) 50 , and W-Ti (W-29at.%Ti, W-40.2at.%Ti and W-48.8at.%Ti) 54 .
…”
The WxTaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.
“…1 ), each particle being much larger than the average grain size of about 13 nm, as shown in the transmission electron microscopy (TEM) micrograph in Fig. 1b ; each powder particle is polycrystalline with nanoscale grains 14 15 16 , which is an important distinction as compared with, for example, nanopowders, where every particle is of nanometre scale dimension and typically is a single crystal, and where some interesting sintering phenomena have also been observed 17 . The selected area diffraction pattern shown in the inset of Fig.…”
Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs.
“…The disappearance of the Cr peaks and the change in W's lattice parameter suggest that the W, Cr, and Fe form a metastable solid solution, in line with previous reports on mechanically alloyed W-Cr and W-Fe couples. [32,33] Similarly to the W-7Cr-9Fe powder, the W lattice parameter in the initially pure W powder changes as Fe dissolves into the W lattice. Figure 1b shows the change in the W-rich solid solution lattice parameter and grain size with time milled for the W-7Cr-9Fe and W-9Fe powders.…”
Section: Powder Characterizationmentioning
confidence: 99%
“…Additionally, one prior study of Cr-doped W reported that a W-30Cr alloy compact had a ~5x smaller grain size than similarly processed pure W compacts after sintering. [32] The Cr can inhibit grain growth in two ways. First, Cr is expected to segregate to grain boundaries in W and thereby lower the driving force for grain growth as well as the grain boundary mobility;…”
Section: Compaction and Compact Microstructurementioning
We report a W-rich alloy (W-7Cr-9Fe, at%) produced by high energy ball milling, with alloying additions that both lower the densification temperature and retard grain growth. The alloy's consolidation behavior and the resultant compacts' microstructure and mechanical properties are explored. Under one condition, a 98% dense compact with a mean grain size of 130 nm was achieved, and exhibited a hardness of 13.5 GPa, a dynamic uniaxial yield strength of 4.14 GPa in Kolsky bar experiments, and signs of structural shear localization during deformation.
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