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β-titanium (β-Ti) alloys are useful in diverse industries because their mechanical properties can be tuned by transforming the metastable β phase into other metastable and stable phases. Relationships between lattice parameter and β-Ti alloy concentrations have been explored, but the lattice parameter evolution during β-phase transformations is not well understood. In this work, the β-Ti alloys, Ti-11Cr, Ti-11Cr-0.85Fe, Ti-11Cr-5.3Al, and Ti-11Cr-0.85Fe-5.3Al (all in at.%), underwent a 400 °C aging treatment for up to 12 h to induce the β-to-ω and β-to-α phase transformations. Phase identification and lattice parameters were measured in situ using high-temperature X-ray diffraction. Phase compositions were measured ex situ using atom probe tomography. During the phase transformations, Cr and Fe diffused from the ω and α phases into the β matrix, and the β-phase lattice parameter exhibited a corresponding decrease. The decrease in β-phase lattice parameter affected the α- and ω-phase lattice parameters. The α phase in the Fe-free alloys exhibited α-phase c/a ratios close to those of pure Ti. A larger β-phase composition change in Ti-11Cr resulted in larger ω-phase lattice parameter changes than that for Ti-11Cr-0.85Fe. This work illuminates the complex relationship between diffusion, composition, and structure for these diffusive/displacive transformations. [ABSTRACT FROM AUTHOR]

Zinc (Zn) alloys, particularly those incorporating magnesium (Mg), have been explored as potential bioabsorbable metals. However, there is a continued need to enhance the corrosion characteristics of Zn-Mg alloys to fulfill the requirements for biodegradable implants. This work involves a corrosion behavior comparison between severe-plastic-deformation (SPD) processed cast Zn-Mg alloys and their hybrid counterparts, having equivalent nominal compositions. The SPD processing technique used was high-pressure torsion (HPT), and the corrosion behavior was studied as a function of the number of turns (1, 5, 15) for the Zn-3Mg (wt.%) alloy and hybrid and as a function of composition (Mg contents of 3, 10, 30 wt.%) for the hybrid after 15 turns. The results indicated that HPT led to multimodal grain size distributions of ultrafine Mg-rich grains containing MgZn2 and Mg2Zn11 nanoscale intermetallics in a matrix of coarser dislocation-free Zn-rich grains. A greater number of turns resulted in greater corrosion resistance because of the formation of the intermetallic phases. The HPT hybrid was more corrosion resistant than its alloy counterpart because it tended to form the intermetallics more readily than the alloy due to the inhomogeneous conditions of the materials before the HPT processing as well as the non-equilibrium conditions imposed during the HPT processing. The HPT hybrids with greater Mg contents were less corrosion resistant because the addition of Mg led to less noble behavior. [ABSTRACT FROM AUTHOR]

Absorbable metals have the potential to serve as the next generation of temporary medical implant devices by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their implementation in the market could greatly reduce the need of costly and risky additional surgeries for either implant replacement or removal, often required in current permanent implants. Despite the extensive research done over the last two decades on magnesium (Mg) and iron (Fe) based alloys, they have not generally shown a satisfactory combination of mechanical properties, biocompatibility and controlled degradation rate in the physiological environment. Consequently, zinc (Zn) based alloys were introduced in the last few years as alternative materials to overcome the limitations of Fe and Mg-based alloys. The blend of different alloying elements and processing conditions have led to a wide variety of Zn-based alloys having tunable mechanical properties and corrosion rates. This review provides the most recent progress in the development of absorbable Zn-based alloys for biomedical implant applications, primarily for cardiovascular and orthopedic devices. Their biocompatibility, processability and metallurgical aspects, as well as their mechanical behavior and corrosion properties are presented and discussed, including their opportunities, limitations and future research directions. Temporary orthopedic bioimplants have become increasingly popular as they offer an alternative to prevent complications, like infections or secondary surgeries, often related to the implantation of permanent devices. Iron and magnesium alloys were extensively studied as candidates for absorbable medical applications, but they generally failed to provide a desirable mechanical performance and corrosion characteristics in the physiological environment. Zinc was introduced in the last decade as a potential implant material after showing outstanding biocompatibility and biodegradability. This review summarizes the research advances to date and provides a thorough discussion of the future challenges of absorbable zinc alloys to satisfy the demanding clinical benchmarks for absorbable medical applications. Their biocompatibility, mechanical, and corrosion aspects, both in vitro and in vivo , are comprehensively reviewed and assessed accordingly. [ABSTRACT FROM AUTHOR]

High-pressure torsion (HPT) was used to investigate the synthesis of Zn-Mg hybrids by direct bonding of separate disks of Zn and Mg at room temperature under an applied pressure of 6.0 GPa after 1, 5, 15 and 30 turns. Microstructural characterisation of the HPT-processed disks showed the formation of a sub-micron multilayered structure embedded in a Zn-rich matrix with an average grain size of ∼ 600 nm at the disk periphery after 30 turns. XRD and TEM analysis revealed the presence of MgZn2 and Mg2Zn11 intermetallic compounds, which increased in volume fractions with increasing number of turns. The formation of these intermetallics, together with Hall-Petch strengthening, led to an exceptional increase of the hardness values after 15 turns. Electrochemical testing in simulated body fluid showed that the degree of plastic deformation had an impact on the corrosion resistance of the Zn-Mg hybrids, which would affect their implementation in the biomedical field for absorbable applications. This study confirmed that there is significant potential for using HPT in the joining of dissimilar metals at room temperature to form Zn-Mg hybrids containing ultrafine-grained metal-matrix heterostructures with enhanced hardness. [ABSTRACT FROM AUTHOR]

The tradeoff between strength and ductility has long been identified as the 'Achilles' heel' of the mechanical properties in engineering applications. Metal hybrids processed by severe plastic deformation (SPD) have gained significant attention in recent years, as they have shown potential for enhancing strength and ductility simultaneously through different heterostructured designs. Among SPD processes, high-pressure torsion (HPT) is considered the most effective in grain refinement and offers excellent versatility for synthesising new materials with a wide variety of experimental setups and processing parameters. This review article describes the current state-of-the-art of metal hybrids processed by HPT, characterised by heterogeneous microstructures (i.e. nanoscale and/or microscale), through a comprehensive study of their synthesis-microstructure-property relationships. The potential of HPT-processed hybrids is highlighted and discussed along with their limitations. Suggestions are provided with the aim to advance current research trends towards future application in high-impact technologies, including the biomedical and microelectronic industries. [ABSTRACT FROM AUTHOR]

Since its discovery in 1954, the omega (ω) phase in titanium and its alloys has attracted substantial attention from researchers. The β-to-ω and ω-to-α phase transformations are central to β-titanium alloy design, but the transformation mechanisms have been a subject of debate. With new generations of aberration-corrected transmission electron microscopy and atom probe tomography, both the spatial resolution and compositional sensitivity of phase transformation analysis have been rapidly improving. This review provides a detailed assessment of the new understanding gained and related debates in this field enabled by advanced characterization methods. Specifically, new insights into the possibility of a coupled diffusional-displacive component in the β-to-ω transformation and key nucleation driving forces for the ω-assisted α phase formation are discussed. Additionally, the influence of ω phase on the mechanical properties of β-titanium alloys is also reviewed. Finally, a perspective on open questions and future direction for research is discussed. [ABSTRACT FROM AUTHOR]

Y, (Y + Nd), and (Y + Ca) multi-microalloying, which has potential to mediate the grain growth and texture evolution, played an important role in the mechanical properties of the studied extruded AZ80 sheet. Quasi-in-situ electron backscattered diffraction results revealed that grain boundary migration and grain rotation simultaneously occurred during the grain growth. All these three microalloying combinations effectively lowered the grain growth rate. In particular, the AZ80 + 0.2Y+0.15Ca maintained the lowest growth rate and the most uniform fine grain structure. The rare-earth (RE) texture components, which temporarily formed in AZ80 + 0.2Y and AZ80 + 0.1Y+0.1Nd, weakened their basal texture intensity. In contrast, continuously enhanced basal texture, accompanied by grain growth, dominated the texture evolution in AZ80 + 0.2Y+0.15Ca. As a result, all microalloyed combinations exhibited lower Vickers hardness than that of AZ80. The microalloying also reduced the hardness anisotropy of the sheets. • (Y + Ca) microalloying dramatically lowers the grain growth rate and homogenizes grain structure in AZ80. • Preferred crystal orientation for the grown grains was prevalent in Y or (Y + Nd) microalloyed AZ80 sheets. • Enhanced basal texture accompanied by grain growth and dominated the annealing texture evolution in AZ80 + 0.2Y+0.15Ca. • The multi-microalloying reduced the hardness anisotropy and degraded the hardness of AZ80 sheets. [ABSTRACT FROM AUTHOR]

Abstract: Slip transfer across the α/β interface was investigated in the near-α titanium alloy Ti–5Al–2.5Sn (wt.%). Globular β-phase grains, located primarily at α-phase grain boundaries, enabled the investigation of the orientation relationship between the α and β phases in the case of a general equiaxed microstructure. Active deformation systems were identified using electron backscattered diffraction (EBSD) supported by plane trace analysis. Information from the plane trace analysis was used to assess a number of metrics that could correlate with α/β slip transfer including: Schmid factors, the angle between slip plane normals (ψ), the angle between active Burgers’ vectors (κ), and the α(0001)/β{110} misorientation angle. From an analysis of 36 β grains, 15 α/β boundaries were found to exhibit the planar α(0001)/β{110} Burgers’ orientation relationship. The α phase, which dominated the microstructure, tended to exhibit slip traces for high global Schmid factor slip systems, including prism, basal, and pyramidal slip planes. When the neighboring β grain was oriented favorably for slip, i.e. exhibited a high Schmid factor, slip transfer was more likely across the α/β interface compared to when the neighboring β phase was not favorably oriented for slip. The alignment between the Burgers’ vectors in the α and β phases was not well correlated with slip across the α/β interface. Furthermore, the boundaries having the α(0001)/β{110} orientation relationship were not necessarily favorable for α/β slip transfer. [Copyright &y& Elsevier]

Processing of metal hybrid nanocomposites have emerged in the recent years by means of solid-state reactions through severe plastic deformation techniques, resulting in heterogenous microstructures and mechanical properties. Despite the increased scientific interest in these unusual materials, little is known regarding their comparative attributes with respect to a homogeneous material having equivalent nominal composition. This work provides a direct comparison of the microstructure and the hardness evolution between a Zn–3Mg (wt.%) alloy and its hybrid counterpart, after high-pressure torsion (HPT) and after HPT followed by a post-deformation annealing (PDA) treatment. Experimental results indicate that both the alloy and the hybrid reach a similar level of grain refinement after HPT processing, however, grain growth follows different trends after PDA. The HPT-processed alloy exhibits clusters of Mg 2 Zn 11 nanocrystalline domains that coalesce into coarser grains maintaining a unimodal GS distribution after PDA. On the other hand, the hybrid after PDA displays a multimodal GS distribution consisting of ultrafine Mg-rich grains containing MgZn 2 and Mg 2 Zn 11 nanoscale intermetallics, in a matrix of coarser dislocation-free Zn grains. These observations were supported by kernel average misorientation (KAM) maps and pole figures obtained through electron backscattered diffraction (EBSD) analysis. • Microstructural evolution is compared between a HPT-processed alloy and its hybrid counterpart. • Heterostructured Zn–Mg hybrid is synthesized via HPT followed by post-deformation annealing (PDA). • Nanocrystalline domains coalesced into coarser grains in the HPT alloy upon PDA. • In-situ precipitation of Mg 2 Zn 11 and MgZn 2 intermetallics ocurred in the hybrid during HPT. • Hardness values and hardness heterogeneity increased after PDA in both the alloy and the hybrid. [ABSTRACT FROM AUTHOR]

Absorbable metals exhibit potential for next-generation temporary medical implants, dissolving safely in the body during tissue healing and regeneration. Their commercial incorporation could substantially diminish the need for additional surgeries and complications that are tied to permanent devices. Despite extensive research on magnesium (Mg) and iron (Fe), achieving the optimal combination of mechanical properties, biocompatibility, and controlled degradation rate for absorbable implants remains a challenge. Zinc (Zn) and Zn-based alloys emerged as an attractive alternative for absorbable implants, due to favorable combination of in vivo biocompatibility and degradation behavior. Moreover, the development of suitable coatings can enhance their biological characteristics and tailor their degradation process. In this work, four different biodegradable coatings (based on zinc phosphate (ZnP), collagen (Col), and Ag-doped bioactive glass nanoparticles (AgBGNs)) were synthesized by chemical conversion, spin-coating, or a combination of both on Zn-3Mg substrates. This study assessed the impact of the coatings on in vitro degradation behavior, cytocompatibility, and antibacterial activity. The ZnP-coated samples demonstrated controlled weight loss and a decreased corrosion rate over time, maintaining a physiological pH. Extracts from the uncoated, ZnP-coated, and Col-AgBGN-coated samples showed higher cell viability with increasing concentration. Bacterial viability was significantly impaired in all coated samples, particularly in the Col-AgBGN coating. This study showcases the potential of a strategic material-coating combination to effectively tackle multiple challenges encountered in current medical implant technologies by modifying the properties of absorbable metals to tailor patient treatments.