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• Microstructure of the alloys is more sensitive to Nb rather than Ta. A slight difference in Nb content will affect the morphology of martensite and even induce ω phase transformation, resulting in completely different mechanical responses of the alloy. • The as-cast Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength (227 ±10 MPa), and compressive strain (74.3% ± 0.4%). • Nb and Ta content strongly affects Young's modulus and tensile properties of the alloys after rolling. The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as more α"-martensite and β-phase, and a good combination of low modulus and high strength among all the designed alloys. Biomedical β-phase Ti-Nb-Ta-Zr alloys usually exhibit low elastic modulus with inadequate strength. In the present work, a series of newly developed dual-phase Ti- x Nb- y Ta-2Zr (wt.%) alloys with high performance were investigated in which the stability of β-phase was reduced under the guidelines of ab initio calculations and d-electronic theory. The effects of Nb and Ta contents on the microstructure, compressive and tensile properties were investigated. Results demonstrate that the designed Ti- x Nb- y Ta-2Zr alloys exhibit typical characteristics of α+β dual-phase microstructure. The microstructure of the alloys is more sensitive to Nb rather than Ta. The as-cast alloys exhibit needle-like α′ martensite at a lower Nb content of 3 wt.% and lamellar α′ martensite at an Nb content of 5 wt.%. Among the alloys, the Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength (2270 ± 10 MPa) and compressive strain (74.3% ± 0.4%). This superior performance is due to the combination of α+β dual-phase microstructure and stress-induced α" martensite. Besides, lattice distortion caused by Ta element also contributes to the compressive properties. Nb and Ta contents of the alloys strongly affect Young's modulus and tensile properties after rolling. The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as more α" martensite and β phase with a good combination of low modulus and high strength among all the designed alloys. Atom probe tomography analysis reveals the element partitioning between the α and β phases in which Ta concentration is higher than Nb in the α phase. Also, the concentration of Ta is lower than that of Nb in the β phase, indicating that the β-stability of Nb is higher than that of Ta. This work proposes modern α+β dual-phase Ti- x Nb- y Ta-2Zr alloys as a new concept to design novel biomedical Ti alloys with high performance. [ABSTRACT FROM AUTHOR]

• High entropy alloy was strengthened by cryo-pre-straining-induced defects. • Strengthening mechanism was quantitatively revealed by neutron diffraction method. • Selective recovery of crystal defects assist to optimize the mechanical performance. Owing to their attractive structure and mechanical properties, high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted considerable research interest. The strength of HEAs/MEAs with a single face-centered cubic (FCC) phase, on the other hand, requires improvement. Therefore, in this study, we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energy-regulated plasticity mechanism. Through neutron diffraction line profile analysis and electron microscope observation, the effect of the tuned defects on the tensile strength was clarified. Due to the cryo-rolling-induced high dislocation density, mechanical twins, and stacking faults, the room-temperature yield strength of an equiatomic CoCrFeNi HEA was increased by ∼290%, from 243 MPa (as-recrystallized) to 941.6 MPa (30% cryo-rolled), while maintaining a tensile elongation of 18%. After partial recovery via heat treatment, the yield strength and ultimate tensile strength decreased slightly to 869 and 936 MPa, respectively. Conversely, the elongation increased to 25.6%. The dislocation density and distribution of the dislocations were found to contribute to the strengthening caused by forest dislocations, which warrants further investigation. This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects. [ABSTRACT FROM AUTHOR]

• The power-law relationship between creep rate decay and time of high-entropy metallic glass can be well described in the framework of shear transformation zones. • Physical aging below the glass transition temperature reduces the number of initial shear transformation zones which contribute to creep. • Cyclic loading can tailor the "forward" jump operations competing with the "backward" ones of shear transformation zones by controlling the recovery time. The power-law relationship between creep rate decay and time is one of the intrinsic characteristics of metallic glasses. In the current work, a La 30 Ce 30 Ni 10 Al 20 Co 10 high-entropy metallic glass was selected as the model alloy to test the influences of physical aging and cyclic loading on the power-law creep mechanism, which was probed by the dynamic mechanical analysis in terms of the stochastic activation, and contiguous interplay and permeation of shear transformation zones. It is demonstrated that a notable discrepancy appears between thermal treatment and mechanical treatment on the power-law creep mechanism of this high-entropy metallic glass. On the one hand, physical aging below the glass transition temperature introduces the annihilation of potential shear transformation zones which contribute to creep. On the other hand, cyclic loading can tailor the "forward" jump operations competing with the "backward" ones of shear transformation zones by controlling the interval time (recovery time). The current research offers a new pathway towards understanding the creep mechanism of high-entropy metallic glasses. [Display omitted] [ABSTRACT FROM AUTHOR]