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NbHfTiVC0.1 refractory high-entropy alloy (RHEA) exhibits excellent comprehensive mechanical properties and demonstrates great potential for applications. However, the mechanical properties need to be improved further. In this work, hot rolling on NbHfTiVC0.1 RHEA at temperatures of 650 °C, 850 °C, and 1050 °C, with total reductions of up to 30%, 50%, 70%, and 80%, was conducted. The microstructure and mechanical property evolution of the samples were further investigated. The hot-rolled samples at 650 °C and 850 °C exhibit a composition consisting of BCC, carbide, and Laves phases, whereas the samples rolled at 1050 °C only consist of BCC and carbide phases. The 650-80 sample displays the highest ultimate tensile strength (1354 MPa), and the 1050-80 sample demonstrates the highest elongation (16%). The highest strength observed in the 650 °C-80% sample can be attributed to the presence of fractured and refined carbides, fine-grains, and the hindrance of dislocation slip by the fine Laves phase. At a higher rolling temperature (1050 °C), the Laves phase disappears, resulting in a reduction in strength but an increase in plasticity. Furthermore, the dislocation slipping mechanism within the BCC matrix also contributes positively to plastic deformation, leading to a notable increase in ductility for the 1050 °C-80% sample. These research findings provide valuable insights into enhancing the strength and ductility simultaneously of NbHfTiVC0.1 RHEA through hot rolling. [ABSTRACT FROM AUTHOR]

Zr-Ti-Nb-Ta alloys were synthesized in parallel via multi-target co-sputtering deposition with physical masking in a pseudo-ternary Ti-Nb-ZrTa alloy system. Sixteen alloys with distinct compositions were obtained. Comprehensive characterization of phase structure, microstructure, Young's modulus, and nanoindentation hardness was undertaken. The Ti-Nb-ZrTa alloys exhibited two typical phase structures: a single-BCC solid-solution structure, and an amorphous structure. Nanoindentation quantification confirmed a Young's modulus ranging from 110 to 130 GPa, alongside nanoindentation hardness spanning 3.6 to 5.0 GPa. The combination of good hardness and a relatively low Young's modulus renders these alloys promising candidates for excellent biomedical materials. This work not only offers an effective method for the high-throughput synthesis of multi-principal element alloys, but also sheds light on a strategy for screening the phase structure and mechanical performance within a given alloy system. [ABSTRACT FROM AUTHOR]

A refractory high entropy alloy (RHEA) NbHfTiV was selected as the master alloy and carbon element was introduced to synthesize the novel NbHfTiVC x RHEAs (x = 0, 0.1, 0.2, 0.3), which perform outstanding strength and excellent ductility simultaneously. Phase identification, microstructure evolution, and mechanical properties were systematically analyzed. The results show that the primary MC-type carbides and nano-precipitate carbides are generated in the BCC matrix phase with the addition of carbon. The primary carbides evolve from solid spheroid (x = 0.1) to sandwich-like pattern (x = 0.2, 0.3), and grain size is significantly refined from 537 µm (x = 0) to 25 µm (x = 0.3). Compressive tests show that the yield strength increases from 958 MPa to 1115 MPa, and the fracture mechanism is changed from ductile fracture to ductile and brittle mixed fracture with carbon content increasing. Meanwhile, the atomic size mismatch and elastic mismatch of the matrix phase reduce with carbon content increasing, which could decrease the lattice distortion degree and soften the matrix phase. [Display omitted] • Carbides (FCC-MC) are generated in BCC matrix with the addition of carbon. • After adding carbon, the grain size is greatly refined from 537 to 25 µm. • Increasing carbon content release severe lattice-distorted and soften the matrix. • Yield strength of NbHfTiVC x RHEAs increase from 958 (C 0) to 1115 MPa (C 0.3). [ABSTRACT FROM AUTHOR]

In the present study, the effect of C micro-alloying on microstructure evolution and properties of metastable immiscible Cu-20Fe alloy was comprehensively investigated. Experimental results indicate that the microstructure of Cu-Fe alloy is extremely sensitive to the C content. It was found that obvious liquid-liquid phase separation (LLPS) behavior is observed in Cu-20Fe alloy after C micro-alloying, and the tendency of LLPS is enhanced with increasing C content. The calculation of ΔScc(0) suggests that C atoms preferentially pair with free Fe atoms to form new Fe (C) atomic clusters, thus resulting in the enhancement of bonding of the like-atom pairs. In addition, the quasi-binary phase diagram calculation further reveals the existence of a stable miscibility gap for C-containing alloys, and the temperature interval of miscibility gap is significantly enlarged with increasing C content. Meanwhile, the interface energy between two liquids formed by LLPS also slightly increases as C content increasing. These above reasons should be responsible for the microstructure evolution of Cu-20Fe-xC alloys. In addition, the C micro-alloying deteriorates the soft magnetic properties of Cu-Fe alloys to a certain extent, whereas improves its corresponding wear-resistance. • The microstructure evolution and solidification behavior of Cu-20Fe-xC alloys were clearly elucidated. • The calculation of ΔScc(0) indicates that C atoms preferentially pair with free Fe atoms to form new Fe(C) atomic cluster. • Phase calculation indicates that the metastable miscibility gap of Cu-20Fe alloy is stabilized by the introduction of C. • The addition of appropriate amount C enhances the wear-resistance of Cu-20Fe alloy. [ABSTRACT FROM AUTHOR]