Powder bed fusion-laser beam (PBF-LB) typically relies on pre-alloyed metallic powders, allowing for precise control over their composition, morphology, and particle size, which are achieved through advanced atomization methods. In-situ alloying in PBF-LB presents a cost-effective solution for developing non-commercial alloys, avoiding complex and costly pre-alloying procedures. One critical aspect to consider when employing in-situ alloying in PBF-LB is achieving microstructure homogenization, which can be influenced by the presence of elemental particles and uneven distribution of alloying elements. In this work, a Ti-30Nb-2.5Sn (wt.%) alloy was produced by PBF-LB using elemental powder blends under two representative processing conditions to elucidate process-microstructure-property relationships. Processing with low laser power and high scanning speed resulted in chemically heterogeneous microstructures containing unmelted Nb particles. These particles locally stabilized the /) phase, induced microstructural gradients, and promoted a-phase precipitation. In contrast, optimized processing conditions yielded a more homogeneous microstructure with columnar prior-/) grains and reduced a-phase formation. The optimized condition exhibited a high as-built ultimate compressive strength of approximately 1303 +/- 117 MPa, exceeding values reported for cast Ti-Nb-Sn alloys. Differential scanning calorimetry revealed overlapping transformation events consistent with the /)-co,so-/)0-a sequence, with reduced thermal activity upon reheating, indicating partial completion of phase transformations. After DSC thermal cycling, only a and /) phases were detected. A systematic gradient in a-plate thickness developed during heat treatment and was attributed to differential oxygen uptake, demonstrating a potential pathway for spatial control of microstructure and mechanical properties. This effect was suppressed in samples containing unmelted Nb particles due to strong local /)-phase stabilization. These findings highlight the critical role of processing parameters in controlling Nb dissolution, phase stability, and microstructural uniformity in in-situ alloyed Ti-Nb-Sn systems processed by PBF-LB.

Complex concentrated alloys (CCAs), including high- and medium-entropy alloys, deform in chemically heterogeneous energy landscapes where dislocation glide, solute aging, twinning, phase transformation and microstructural barriers may all contribute. This review discusses avalanche-like and serrated plasticity in CCAs across scales. The first part separates the relevant length scales and methods used to access them. At microscopic and mesoscopic scales, acoustic emission (AE) and microcompression studies reveal discrete dislocation avalanches and strain bursts that may be hidden in conventional macroscopic curves. At the specimen scale, local extensometry and digital image correlation (DIC) studies of the Portevin-Le Chatelier effect show how collective defect dynamics can organize into deformation bands and macroscopic stress serrations. Together, these approaches show that plastic flow may appear smooth only as an average response, while remaining intermittent at finer scales. The second part reviews direct CCA evidence, with emphasis on AE, stress-serration statistics, microplasticity, DIC, nanoindentation and small-scale deformation. A central conclusion is that serrated flow in CCAs should not be treated as a single phenomenon. Depending on chemistry, temperature, strain rate and microstructure, it may originate from dynamic strain aging, twinning, martensitic transformation, slip localization, or a combination of these mechanisms. Reported power-law-like distributions and exponents partly overlap with those known from simpler crystals and alloys, and the present evidence does not establish a distinct CCA-specific universality class. CCAs are therefore best viewed as tunable systems in which chemical disorder, short range order, phase stability and microstructure can modify the nucleation, arrest and synchronization of collective plastic events.

Metastable titanium alloys containing molybdenum (Mo) are promising for biomedical applications due to their superior mechanical properties. To investigate the influence of Mo content on thermomechanical processing, the deformation mechanisms in Ti-Mo alloys were analysed using hot compression experiments performed on Ti-12Mo and Ti-18Mo. Tests were carried out in both the alpha+beta-and beta-phase regions over a temperature range of 610 degrees C-910 degrees C and at strain rates from 0.01 s(-1)-10 s(-1), up to a true strain of 0.80, followed by immediate water quenching. Microstructural characterisation of samples tested in the alpha+beta-and beta-phase regions was performed using scanning electron microscopy images and electron backscatter diffraction measurements, respectively. Flow curves in the beta-phase region display pronounced work hardening, a behaviour rarely observed in beta-Ti alloys, which is likely attributed to suppressed dynamic recovery influenced by Mo. In alpha+beta-phase deformation, flow curves exhibit softening after reaching peak values, corresponding to morphological changes in the alpha phase. Due to the slow diffusivity of Mo, subgrain formation and alpha-phase globularisation were primarily confined to prior beta grain boundaries, resulting in a heterogeneous deformed microstructure. The extent of dynamic recovery, subgrain size, and dynamic alpha-phase globularisation were quantified and compared between the investigated alloys. Mo retards dynamic recovery and alpha-phase globularisation, increasing strength in the beta-phase region but reducing it in the alpha+ beta region.

The development of femoral stems for hip implants with a gradient in chemical composition offers a promising strategy to mitigate the stress shielding effect by tailoring mechanical properties along the stem. To identify optimal alloy compositions, comprehensive experimental characterization is essential. In this study, ten distinct alloys of the metastable beta Ti-Nb-Fe-Sn alloy family were fabricated using powder bed fusion via laser beam (PBF-LB) under nine different processing conditions. The printed specimens were systematically investigated to determine the most favorable conditions for further development of a compositionally graded implant. Microstructural analysis revealed that processing at 100 mm/s scan speed and 100 W laser power yielded equiaxed grains and homogeneous composition. Elastic properties determined by resonant ultrasound spectroscopy showed a composition-dependent Young's moduli ranging from similar to 60 to 100 GPa. Microhardness results indicated strengthening of single phase beta material by Fe additions with values between similar to 250 and 320 HV. These findings demonstrate that PBF-LB can produce Ti-Nb-Fe-Sn alloys with tunable properties suitable for graded implant design, providing low modulus compositions for the distal side (inserted into the bone) and high strength on the proximal side (neck).

This work presents a finite-strain version of an established three-dimensional constitutive model for polycrystalline shape memory alloys (SMA) that is able to account for the large deformations and rotations that SMA components may undergo. The model is constructed by applying the logarithmic strain space approach to the original small-strain model, which was formulated within the Generalized Standard Materials framework and features a refined dissipation (rate) function. Additionally, the free energy function is augmented to be more versatile in capturing the transformation kinetics. The model is implemented into finite element software. To demonstrate the model performance and validate the implementation, material parameters are fitted to the experimental data of two SMA, and two computational simulations of SMA components are conducted. The applied approach is highly flexible from the perspective of the future incorporation of other phenomena, e.g., irreversibility associated with plasticity, into the model.

The conventional manufacturing of refractory complex concentrated alloys (RCCAs) for high-temperature applications is complicated, particularly when material costs and high melting points of the materials processed are considered. Additive manufacturing (AM) could provide an effective alternative. However, the extreme temperatures involved represent significant challenges for manufacturing defect-free alloys using this approach. To address this issue, we investigated the preparation of a CrNbTiZr quaternary complex concentrated alloy from an equimolar blend of elemental powders using commercially available powder-blown L-DED technology. Initially, the alloys exhibited some defects owing to the internal stress caused by the temperature gradients. This was subsequently resolved by optimizing the deposition strategy. SEM, XRD and EDS were used to analyze the alloy in the as-deposited condition, revealing a BCC phase and a secondary Laves phase. Furthermore, Vickers hardness testing demonstrated a correlation between the hardness and the volume fraction of the Laves phase. Finally, successfully performed compression tests confirmed that the prepared material exhibits high-temperature strength and therefore is promising for high-temperature application under extreme conditions.

Controlled mechanical loading was applied to Ti-15Mo alloy during annealing at 550 degrees C. Massive formation of the wiso phase from the parent (3-phase occurred during annealing without external stress or with stress well below the yield stress. Moreover, a massive alpha phase precipitation takes place under simultaneous annealing and plastic deformation. Plastic deformation plays a key role in (3- alpha transformation and achieving refined alpha + (3 type microstructure resulted in improved mechanical properties. Studying phase transformations during plastic deformation is critical for understanding and optimizing thermomechanical processing of metastable (3-Ti alloys.

The microstructure and mechanical properties of Cr-Nb-Ti-Zr complex concentrated alloy (CCA) prepared from the blend of elemental powders by laser directed energy deposition (L-DED) technique were investigated. Variation of the laser power and laser-induced substrate platform preheating were utilized to deposit 3D bulk samples. Deposition at maximum laser power of 500 W followed by long-term homogenization heat treatment at 1200 degrees C results in the crack free, locally homogeneous material. The final chemical composition of the deposited sample Cr15-Nb28-Ti23-Zr34 differs from the equimolar composition of the blended elemental powders due to Cr evaporation during deposition. The homogenized microstructure is formed by equiaxed grains with the size below 100 mu m and fine Cr2(Zr, Nb, Ti) Laves phase particles dispersed predominantly at grain boundaries. Mechanical properties were investigated by compression tests at RT, 400 degrees C and 800 degrees C. At RT, the homogenized alloy exhibits yield stress of 1558 MPa (ductility is about 8 %). Deformation at 400 degrees C decreases the yield stress by 20 %, while the ductility remained unchanged. Serrated flow appearing at compression curves at 400 degrees C can be attributed to the PLC effect. It was shown that L-DED technique can produce refractory CCAs directly from elemental powders by careful optimization of processing parameters. Deposition with a thermally insulating platform effectively suppresses crack formation and reduces the number of unmelted Nb particles. However, the utilization of the homogenization heat treatment after the deposition is required to achieve microstructural homogeneity at the length-scale of powder particles (tens of micrometers).

Near-(3 titanium alloys have shown low Young's modulus and good strength, making them excellent implant candidates. However, their processing using thermomechanical routes in single phase (3 region results in heterogeneous microstructures due to high content alloying elements and consequent slow diffusion-controlled processes such as dynamic recovery. This study investigates the deformation behaviour of a Ti-15Mo alloy through hot compression experiments using a Gleeble (R) 3800 device in the single (3 domain at strain rates from 0.01 s- 1 to 10 s- 1, reaching final strains of 0.50 and 0.85 followed by immediate water quench. The findings show that the material presents a low strain rate sensitivity. The flow curves show significant strain hardening before reaching a steady-state regime, particularly at high strain rates. The strain hardening exponent calculations support the effect of molybdenum on retarding softening mechanisms such as dynamic recovery. Electron backscatter diffraction (EBSD) measurements of deformed samples revealed that dynamic recovery is the primary restoration mechanism, with continuous and geometric dynamic recrystallisation evidence. Due to the slow restoration process, we observe the subgrain formation for different deformation parameters. Therefore, we introduced an EBSD-based method to quantify dynamic recovery and subgrain size. We concluded that for a given deformation, the areas of dynamically recovered and recrystallised regions decrease with increasing strain rate and decreasing temperature, exhibiting negligible variation at higher strain rates.

The spatial orientation of α lamellae in a metastable β-Ti matrix of Timetal LCB (Ti–6.8 Mo–4.5 Fe–1.5 Al in wt%) was examined and the orientation of the hexagonal close-packed α lattice in the α lamella was determined. For this purpose, a combination of methods of small-angle X-ray scattering, scanning electron microscopy and electron backscatter diffraction was used. The habit planes of α laths are close to {111}β, which corresponds to (1320)α in the hexagonal coordinate system of the α phase. The longest α lamella direction lies approximately along one of the 〈110〉β directions which are parallel to the specific habit plane. Taking into account the average lattice parameters of the β and α phases in aged conditions in Timetal LCB, it was possible to index all main axes and faces of an α lath not only in the cubic coordinate system of the parent β phase but also in the hexagonal system of the α phase.

Compositional boundaries of activity regarding transformation-induced plasticity and mechanical twinning (TRIP/TWIP) in Ti-Nb alloying system is determined by a novel methodology using chemically graded samples prepared by Spark Plasma Sintering. Presented methods of characterization include nanoindentation and microindentation testing complemented by EBSD analyses. The link between composition, microstructure, deformation mechanisms and mechanical properties can be established. Applied to the Ti-Nb system for a proof of concept, both the identification of local mechanical properties with respect to composition, and the refinement of the compositional ranges within which the different deformation mechanisms occur can be obtained. The graded sample ranging from 14 at.% to 34 at.% Nb is studied. TRIP/TWIP activity is resolved by EBSD in range 17 to 24 at.% of Nb, which is significantly lower than the results from the literature. This difference is attributed to the presence of interstitial oxygen (2470 +/- 60 weight ppm).

The field-assisted sintering technique (FAST) was successfully used to sinter, homogenize, and age the Ti–5Al–5V–5Mo–3Cr (Ti-5553) aerospace alloy from blended elemental powders in a single processing run. Sintering at a comparatively high temperature of 1500 °C assured chemical homogeneity of the material. Subsequently, without cooling to the room temperature, the temperature was lowered to 600 °C for 30 min to provide annealing treatment and to produce a desired lamellar α + β microstructure. Using an in-house designed assembly, a fully dense rod of 15 mm in diameter and 70 mm in length was successfully sintered. Microstructural and mechanical properties of the alloy were investigated and compared with the conventionally processed Ti-5553 alloy. A good combination of strength (1183 MPa) and ductility (6 pct) was achieved; these values are fully comparable to the conventional cast, forged, and aged Ti-5553 alloy. It was shown that homogeneous Ti-5553 alloy can be produced by FAST, FAST can instantly provide necessary annealing steps, and the FAST process can be upscaled to produce homogeneous rods.

The field-Assisted sintering technique (FAST), also known as spark plasma sintering, is a fast consolidation powder metallurgy technique for conductive and non-conductive materials. However, FAST is commonly used for the manufacture of small specimens. The present work presents the feasibility of sintering larger rods of a biomedical Ti-15Mo alloy using FAST. By implementing an adequate die arrangement, long rods of nearly 80 mm in length and 15 mm in diameter were sintered in less than 30 min with a densification above 95%. Power consumption to produce larger samples is compared with that for typical small-processed specimens. However, microstructural features appeared due to the pressure and temperature distributions, inherent to the technique. The results highlight the opportunities and drawbacks of using FAST for the consolidation of larger specimens, while the microstructural and mechanical performance of the as-sintered and post-processed Ti-15Mo rods are given and compared to a conventionally prepared alloy.

The effect of high pressure torsion processing on mechanical properties and corrosion behavior of pure magnesium and Mg-Zn, Mg-Zn-Ca, Mg-Li-Y and Mg-Y-RE alloys is investigated. Micro-tomography and SEM characterization are used to estimate corrosion rate and evaluate non-uniform corrosion features. The results show that severe plastic deformation processing improves the strength of all magnesium alloys, but deformation localization can take place in the Mg-Zn-Ca and Mg-Y-RE alloys. The occurrence of deformation localization is associated with low strain rate sensitivity in these alloys and with severe corrosion localization. Pure magnesium and Mg-Zn and Mg-Li-Y alloys display good corrosion resistance with a low corrosion rate and maintain integrity after 28 days of immersion in Hank's solution.

Compositionally graded Ti(4–12 wt% Mo) alloys were successfully prepared by laser directed energy deposition (L-DED) using two hoppers from Ti and Ti-15Mo master alloy powders. Detailed SEM, EDS and XRD analysis reveals the variation of the microstructure and consequently explains the evolution of the microhardness with the Mo concentration. High laser power is required to dissolve Ti-15Mo particles, to improve the homogeneity of the material at the scale of particle size, and to achieve a smooth linear gradient of the chemical composition. In the bottom part of the samples, the microstructure consists of elongated beta grains of the length of several mm containing big α-Ti laths. With increasing Mo concentration, the volume fraction of α phase decreases. Starting from the composition of about 9 wt% Mo the presence of ω phase was detected. Microhardness values span over a wide range of 270–550 HV and are affected by phase composition. The highest values of microhardness are achieved at around 10 wt% of Mo. However, phase composition and microhardness depend also on the utilized laser power and position in the sample determining the cooling rates. L-DED is capable of producing functionally graded materials (FGM) on the basis of metastable β-Ti alloys providing large variations of mechanical properties within a single sample/product.

Small-angle X-ray scattering (SAXS) is a technique which makes use of elastic scattering of X-ray radiation on inhomogeneities in electron density in the studied material In particular, a difference in chemical compositions between individual phases can be detected. In this research, SAXS was used to study the evolution of α particles in aged samples of a metastable β titanium alloy, Ti-6.8Mo-4.5Fe-1.5Al (LCB). In order to obtain scattering patterns for a known crystallographic orientation, the experiments were carried out on single crystals grown by a floating zone technique. Aged single-crystalline samples were measured in three different orientations, namely (001), (110) and (111) planes of the bcc β matrix oriented perpendicularly to the primary beam. Resulting scattering patterns exhibited symmetries which correlated with the orientation of the studied sample. A simple theoretical model was developed to interpret the shape and orientation of the observed scattering streaks. Good qualitative agreement between experimental data and simulation was found and the first results of the model are presented in this paper.

Elastic constants of dual-phase β-titanium alloys with different phase compositions and different volume fractions of individual phases were investigated using resonant ultrasound spectroscopy and transient grating spectroscopy. It was shown that even for high volume fractions of the secondary phases (ω and α), the crystals can retain cubic symmetry and homogeneity in their elastic behavior, both at the macro-scale and at the micro-scale, unless the secondary phases precipitate under external stress violating this symmetry. In contrast, a material heat-treated under uniaxial compression deviates from cubic symmetry in its macroscopic behavior, and its micro-scale elastic behavior is heterogeneous. The results also reveal that the ω and α particles have different impacts on the elastic constants of the β−matrix, the former affecting only the shear part of the elastic response, while the latter also the bulk modulus.