The strain rate effect (2.8 × 10−5–2.8 × 10−1 s−1) on the tensile properties and microstructure evolution of a β-type Ti-10Mo-1Fe (wt%) alloy has been investigated. With increasing strain rate, the yield strength increased, while the ultimate tensile strength, total elongation and uniform elongation decreased. It was found that deformation at a lower strain rate led to an enhanced work hardening rate (θ). This is reflected in the decreasing strain rate sensitivity of flow stress, m, with increasing strain. Strain rate sensitivity was positive at a smaller strain level (< 0.13), and decreased to a negative at a larger strain. The strain rate dependence of work-hardening behavior has been investigated and discussed in terms of the microstructure evolution, such as {332}<113> twins and dislocations. Electron Backscattered Diffraction (EBSD) and X-ray diffraction (XRD) analyses revealed lower increasing rates of {332}<113> twins and dislocation density at higher strain rates, which may be caused by adiabatic heating. This may lead to the reduced work-hardening rate on deformation at the higher strain rates.

•High-pressure torsion caused structural rejuvenation in Zr-Cu-Al-Ni metallic glasses.•Structural rejuvenation was verified by the increase in relaxation enthalpy.•Larger relaxation enthalpy was observed in composition with lower Zr/Cu ratio.•Metallic glass with higher fragility could be more susceptible to rejuvenation.With the aim of studying the effect of composition on structural rejuvenation, high-pressure torsion was performed on Zr55Cu30Ni5Al10 and Zr65Cu18Ni7Al10 metallic glasses. Nanoindentation measurements showed that structural rejuvenation in these two alloys was accompanied by a transition in deformation mode from localized deformation to a more homogenous deformation. The rejuvenated samples also exhibited strain-softening and improved plasticity. The increase in relaxation enthalpy of Zr55Cu30Ni5Al10 metallic glasses was larger than that of Zr65Cu18Ni7Al10, indicating different extents of structural rejuvenation. The influence of composition on the extent of structural rejuvenation was assessed for different systems of metallic glasses in the literature from the perspective of atomic clusters and liquid fragility. It was concluded that metallic glasses formed from more fragile liquids could be more susceptible to mechanically-induced rejuvenation.

•High-pressure torsion causes solid-state amorphization in Zr-Cu-Al crystalline alloy.•The HPT-amorphized alloy exhibits homogenous deformation but weak thermal stability.•Structural rejuvenation happens concurrently with solid-state amorphization.The aim of this study is to compare the difference between the amorphous phases produced by difference fabrication methods: melt quenching (MQ) and solid-state amorphization (SSA). SSA by high-pressure torsion (HPT) was achieved in a crystalline Zr-40at%Cu-10at%Al alloy. The sample deformed by 100 turns of HPT consisted of mostly amorphous phase with τ5 nanocrystals embedded in the amorphous matrix. Compared to the MQ metallic glass, the SSA sample showed lower Vickers microhardness and homogenous plastic flow without shear bands under nanoindentation. Furthermore, the SSA sample exhibited a lower onset temperature of structural relaxation and larger relaxation enthalpy as measured by differential scanning calorimetry. These differences in mechanical and thermal properties can be attributed to the structural rejuvenation occurred concurrently with solid-state amorphization.

•Phase stabilities of β, α phases and compounds in Ti alloys were explicitly compared.•Alloying element dependence of the elastic properties were accurately determined.•The electronic structures of Ti alloys were systematically analyzed.•Temperature effect related to mixing entropy is significant to stabilize the phases.Phase stability and elastic properties of Ti1-x-Xx alloys (X = substitutional Mo, Nb, Al, Sn, Zr, Fe, Co, and interstitial O) in body-centered cubic (bcc) (β phase) and hexagonal close-packed (hcp) (α phase) crystal structures were studied using first-principles calculations. The formation energy was used to determine the dependence of the phase stability on the atomic concentration x (0 ≤ x ≤ 0.5 for substitutional elements and 0 ≤ x < 0.02 for O) of the alloying elements and atomic configurations (ordered, disordered, and other compound structures). The disordered configurations of the atoms in the alloys were considered within the framework of the special quasi-random structures (SQS) method. The composition dependence of elastic constants, isotropic elastic moduli and density of states (DOS) were also evaluated.The predicted formation energies and elastic properties agrees well with previous experimental and theoretical results. Addition of Mo was found to stabilize the β phase significantly while destabilizing the α phase. Nb was found to be a weaker β-stabilizer. In Ti-Al and Ti-Sn systems, the compounds form preferentially at a higher concentration. Zr shows little effect on the phase stability, thus Zr is a neutral element. For Ti-O systems, the octahedral site is the most stable site for interstitial oxygen in both bcc and hcp structures. The comparison of formation energies showed that O acts as an α stabilizer. Considering the configurational entropy contribution, we concluded that temperature effect can be significant to stabilize the phases. The elastic constants calculation revealed that adding Mo, Nb, Fe, or Co increases the mechanical stability of bcc Ti, whereas bcc Ti-Al, Ti-Sn, and Ti-Zr systems are mechanically unstable for all the calculated concentrations. For their hcp counterparts, Ti-Mo and Ti-Nb have lower mechanical stability than the Ti-Al, Ti-O, and Ti-Sn systems. It was found in the electronic structures calculation that increasing addition of Nb, Mo, Fe, and Co weakens the covalent-like bonding of hcp system and strengthens the metallic bonding of bcc system. This variation of the TDOSs of these Ti alloys explains why the bcc phase becomes more stable than the hcp phase at high concentration. Due to the similarity of electronic structure, Zr does not change the DOS of the bcc and hcp phases significantly: The Fermi level in DOS profile of Ti-Zr was found to be identical to that of pure Ti system. Ti-Al and Ti-Sn alloys keep the covalent-like bonding, which explains why hcp Ti-Al and Ti-Sn are stable.

A ultrafine-grained structure was produced in a Mg–3.4Zn (at.%) alloy subjected to high-pressure torsion (HPT) at ambient temperature. Hardness and X-ray diffraction measurements indicated the microstructure reached a steady state after three revolutions. Transmission electron microscopy observations showed equiaxed, dynamically recrystallized grains with an average diameter of 140 nm after 20 revolutions, substantially less than the steady-state grain size in pure Mg deformed by HPT. This is attributed to the formation of precipitates during processing, which impedes the growth of recrystallized grains.

The microstructures and mechanical properties of amorphous/nanocrystalline hybrid TiNi wires produced by severe cold drawing were investigated. Annealed wires of Ti-50.9 mol%Ni and Ti-41 mol%Ni-8.5 mol%Cu were subjected to severe cold drawing of 50-70% reduction. The as-drawn TiNi wires were composed of the mixture of amorphous phase and predominantly B2 nanocrystalline phase. Young’s modulus increased with the drawing reduction which can be attributed to the increase in the amount of amorphous phase. For the binary TiNi wires, the volume fraction of amorphous phase was estimated to be about 60% from Young’s modulus and electrical resistivity. The wires drawn over 60% exhibited peculiar large linear elastic strain which is quite different from superelasticity. Aging at 573 K led to an increase in tensile elongation as well as in the recoverable strain. The amorphization by cold drawing was also confirmed for Ti-41 mol%Ni-8.5 mol%Cu in 62% drawn wires.

The microstructure and properties of Ti–50.9 mol.% Ni wires after severe cold drawing were studied. X-ray diffractometry, transmission electron microscopy and electrical resistivity measurements revealed that the amorphous phase was dominant in the as-drawn wires. Young’s modulus depended strongly on the drawing reduction. The amorphous/nanocrystalline wires after 70% reduction exhibit high tensile strength (>2 GPa), a high Young’s modulus (71 GPa) and a large pseudoelastic recovery strain (∼3%). The recovery strain was further improved to 5.8% by aging at 573 K.