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In this study, the effects of spinodal decomposition on the microstructures and mechanical properties of a TiZrNbTa alloy are investigated. The as-cast TiZrNbTa alloy possesses dual phases of TiZr-rich inter-dendrite (ID) and NbTa-rich dendrite (DR) domains, both of which have a body-centered cubic (BCC) structure. In the DRs of the as-cast alloy, the α and ω precipitates are found to be uniformly distributed. After homogenization at 1100 °C for 24 h followed by water quenching, spinodal decomposition occurs and an interconnected structure with a wavelength of 20 nm is formed. The α and ω precipitates remained in the structure. Such a fine spinodal structure strengthens the alloy effectively. Detailed strengthening calculations were conducted in order to estimate the strengthening contributions from the α and ω precipitates, as well as the spinodal decomposition microstructure. [ABSTRACT FROM AUTHOR]

Abstract In this study, creep behavior of the face-centered-cubic (FCC) {111} and {100} grains in single-phase Fe 20 Co 20 Ni 20 Cr 20 Mn 20 and dual-phase Fe 18 Co 18 Ni 20 Cr 18 Mn 18 Al 8 high-entropy alloys (HEAs) was evaluated using a nanoindentation method over temperatures range of 300–600 °C. We measured the creep response of the two different grain orientations in the two alloys in order to study the orientation and solid-solution effects. Creep stress exponent (∼3.8–5.0) and activation energy (240–260 kJ/mol) were extracted and analyzed from stain rate-stress and stain rate-temperature data to provide information on the creep mechanism. The results indicated that creep was controlled by dislocation climb in both alloys at both orientations. However, we pointed out that, based upon activation energy value alone, it was difficult to identify which elemental constituent would be the dominant diffusing species responsible for vacancy diffusion during the climb. It was found that creep activation volume for the current two HEAs (140 Å3 or ∼12Ω, where Ω is the atomic volume) at 600 °C is larger than that reported for the Ni-based superalloys (∼50–100 Å3 or less) within a similar temperature range. The significance of this larger activation volume is also discussed. Graphical abstract Image 1 Highlights • Nanoindentation creep responses in high entropy alloys are examined over 300–600 °C. • The extracted activation energy under the constant stress condition is around 260 kJ/mol. • The current high entropy alloys possess relatively large volume about 140 Å3 at 600 °C. [ABSTRACT FROM AUTHOR]

The Ti x (AlCrVNb) 100-x (x = 20, 40, 60 and 80) low-density multi-principal element alloys (MPEAs) were prepared by vacuum arc-melting. The density, crystal structure, microstructure and mechanical properties of this new Ti x (AlCrVNb) 100-x are reported. The density of alloys decreases with increasing Ti content from 5.81 to 4.79 g/cm3. The microstructure of Ti20 consists of body-centered cubic (BCC) and minor amount of nano-sized particles segregating at grain boundaries, resulting in the brittleness of Ti20. But Ti40, Ti60 and Ti80 all consist of a single BCC solid solution phase. In addition, the experimentally observed phase constitutions are compared with the equilibrium and non-equilibrium thermodynamical modeling results. The compression yield strength decreases from 1122 MPa for Ti40 to 600 MPa for Ti80, due to the decreased atomic size difference. The combination of room-temperatured specific strength and ductility of Ti40 was found to be superior to most single-phase BCC MPEAs in the as-cast state. Promising room-temperature tensile properties were found for Ti60, better than those of most single-phase BCC MPEAs. The solid solution strengthening was found to be the dominant strengthening mechanism, making up more than 90% of the yield strength of Ti40–Ti80. Image 1 • A new light weight multi-principal element alloy TiAlCrVNb is successfully developed. • The phase evolution and mechanical response as a function of composition are explored. • The solid-solution hardening contributes more than 90% of the yield strength. [ABSTRACT FROM AUTHOR]