TREATMENTS AND METHODS FOR IMPROVING BIOFUNCTIONAL PROPERTIES OF TITANIUM ALLOYS

Optimization of microstructure during deformation processing using control theory principles

7 - Severe plastic deformation and the production of nanostructured alloys by machining

A class of deformation processing applications based on the severe plastic deformation (SPD) inherent to chip formation in machining is described. The SPD can be controlled, in situ, to access a range of strains, strain rates, and temperatures. These parameters are tuned to engineer nanoscale microstructures (e.g., nanocrystalline, nanotwinned, and bimodal) by in situ control of the deformation rate. By constraining the chip formation, bulk forms (e.g., foil, sheet, and rod) with nanocrystalline and ultrafine grained microstructures are produced. Scaling down of the chip formation in the presence of a superimposed modulation enables production of nanostructured particulate with controlled particle shapes, including fiber, equiaxed, and platelet types. The SPD conditions also determine the deformation history of the machined surface, enabling microstructural engineering of surfaces. Application of the machining-based SPD to obtain deformation-microstructure maps is illustrated for a model material system—99.999% pure copper. Seemingly diverse, these unusual applications of machining are united by their common origins in the SPD phenomena prevailing in the deformation zone. Implications for large-scale manufacturing of nanostructured materials and optimization of SPD microstructures are briefly discussed.

Mechanical properties, structural and texture evolution of biocompatible Ti–45Nb alloy processed by severe plastic deformation

Austenitic 317L stainless steel was favored in many industrial applications due to its excellent corrosion resistance and mechanical properties. The study involved heat treating Austenitic 317L stainless steel samples at temperatures of 500℃, 950℃, and 1100℃ to explore the effects of heat treatment temperature on microstructure and corrosion resistance. Electrochemical analysis showed that the 317L sample treated at 1100℃ exhibited the lowest passive current density, indicating the best improvement in corrosion resistance at this temperature. Results from corrosion weight loss experiments confirmed that the least weight loss occurred under the heat treatment conditions of 950℃ and 1100℃, suggesting enhanced corrosion resistance of the material. Microstructural characterization revealed that after heat treatment at 950℃, the metallographic structure transformed from a complex, irregular size and chaotic growth pattern to uniformly grown and comparatively equal-sized metallographic structures. Furthermore, heat treatment at 1100℃ resulted in larger metallographic structures with reduced boundary width and distribution density. Consequently, enhanced corrosion resistance was observed at both temperatures. Based on these findings, a heat treatment range of 950℃ to 1150℃ appeared to be a suitable post-processing method for optimizing the microstructure of 317L while concurrently improving its corrosion resistance.

The striving for the independence of fossil energy sources by further development of renewable energies as well as the change in mobility act as a driving force on technological innovations. Magnetic materials with improved magnetic efficiency help to push the limits for optimized, low‐loss power conversion applications and electrification. Besides improving the chemical composition, that is, gaining better performance using alloys reduced or free of heavy rare earth elements, microstructure optimization has proven to be a crucial field of research. In order to better control the grain size, phase distribution and texture of the polycrystalline material, new process routes, such as severe plastic deformation, need to be investigated and explored in addition to the state‐of‐the‐art method – sintering. Here, attention must be paid to the possible formation of soft magnetic α‐Fe after the casting process prior to the actual deformation step, as these secondary phases negatively affect the hysteretic behavior of the magnet. Assistance in the analysis of the underlying magnetic mechanisms is provided by micromagnetic theory. Besides the reliable prediction of the magnetization distribution on micron‐scale, especially in a multi‐phase microstructure, it also allows for the analysis of the magnetic hysteresis behavior. This work provides a micromagnetic simulation frame work based on a finite element scheme. Relying on this framework the effective hysteresis behavior of two different heterogeneous microstructures (Nd2Fe14B and Nd2Fe14B/α‐Fe) are analyzed and compared.

Revealing the influence of pre-precipitation microstructure on hot workability in an Al-Cu-Mg-Zr alloy

Two-dimensional MoSe2 is a promising candidate for lithium-ion battery anodes. However, its conductivity and lithium storage volumetric effect still need to be optimized. In this work, W-doped MoSe2/rGO paper-like microspheres are successfully prepared through ultrasonic spray pyrolysis, achieving optimization at both the microstructure and mesostructure to enhance the lithium storage performance of the material. Firstly, by utilizing the similar two-dimensional structure between MoSe2 and rGO, self-assembly is achieved through spray pyrolysis, resulting in a well-defined van der Waals heterostructure at the interface on the microscale, enhancing the electron and ion transfer capability of the composite. Secondly, the mesoscale paper-like microsphere morphology provides additional volume expansion buffering space. Moreover, W-doping not only increases the interlayer spacing of MoSe2 (0.73 nm), thereby reducing the diffusion resistance of Li+, but also allow for the modulation of the energy band structure of the material. Density functional theory (DFT) calculations confirm that W-doped MoSe2/rGO exhibits the narrowest bandgap (0.892 eV). Therefore, the composite demonstrates excellent lithium storage performance, maintaining a specific capacity of 732.9 mAh·g−1 after 300 cycles at a current density of 1 A·g−1.Graphical abstract

Metals produced by Severe Plastic Deformation (SPD) offer distinct advantages for medical applications such as orthopedic devices, in part because of their nanostructured surfaces. We examine the current theoretical foundations and state of knowledge for nanostructured biomaterials surface optimization within the contexts that apply to bulk nanostructured metals, differentiating how their microstructures impact osteogenesis, in particular, for Ultrafine Grained (UFG) titanium. Then we identify key gaps in the research to date, pointing out areas which merit additional focus within the scientific community. For example, we highlight the potential of next-generation DNA sequencing techniques (NGS) to reveal gene and non-coding RNA (ncRNA) expression changes induced by nanostructured metals. While our understanding of bio-nano interactions is in its infancy, nanostructured metals are already being marketed or developed for medical devices such as dental implants, spinal devices, and coronary stents. Our ability to characterize and optimize the biological response of cells to SPD metals will have synergistic effects on advances in materials, biological, and medical science.

Enhancing corrosion resistance and biocompatibility of interconnected porous β-type Ti-24Nb-4Zr-8Sn alloy scaffold through alkaline treatment and type I collagen immobilization

Influence of ultrasonic shot peening on corrosion behavior of 7075 aluminum alloy

Plasma Electrolytic Oxidation (PEO) is a cutting‐edge method for creating ceramic‐like protective coatings on valve metals like magnesium (Mg), titanium (Ti), or aluminum (Al). These coatings exhibit exceptional wear resistance, corrosion protection, and high‐temperature stability, making them indispensable for applications in biomedical, aerospace, and automotive industries. However, the PEO process alone does not fully determine the quality, effectiveness, and performance of these coatings, the surface preparation of the substrate before coating is equally critical. Proper surface pretreatment is essential for achieving optimal adhesion, microstructure, and uniformity of the coatings. Surface pretreatment techniques such as heat treatment, severe plastic deformation (SPD), laser surface modification, chemical immersion, cold spray deposition, and magnetron sputtering have been widely explored to optimize the interfacial bonding and microstructural characteristics of PEO coatings. Understanding the intricate relationship between pretreatment strategies, substrate properties, and PEO process parameters is key to developing coatings with superior corrosion resistance, mechanical integrity, and defect control. This review provides a comprehensive evaluation of various pretreatment methods applied prior to PEO on Mg alloys, assessing their influence on coating morphology, phase composition, electrochemical behavior, and tribological performance. Furthermore, critical challenges and future research opportunities is identified in this domain, particularly in the development of hybrid pretreatment approaches and multifunctional coatings. By refining these processes, researchers can unlock new pathways for enhancing the durability and functionality of Mg alloys in extreme environments, expanding their industrial applicability.

The development of micro- and nanostructured surfaces which improve the cell–substrate interaction is of great interest in today's implant applications. In this regard, Al/Al2O3 bi-phasic nanowires were synthesized by chemical vapor deposition of the molecular precursor (tBuOAlH2)2. Heat treatment of such bi-phasic nanowires with short laser pulses leads to micro- and nanostructured Al2O3 surfaces. Such surfaces were characterized by scanning electron microscopy (SEM), electron dispersive spectroscopy and x-ray photoelectron spectroscopy. Following the detailed material characterization, the prepared surfaces were tested for their cell compatibility using normal human dermal fibroblasts. While the cells cultivated on Al/Al2O3 bi-phasic nanowires showed an unusual morphology, cells cultivated on nanowires treated with one and two laser pulses exhibited morphologies similar to those observed on the control substrate. The highest cell density was observed on surfaces treated with one laser pulse. The interaction of the cells with the nano- and microstructures was investigated by SEM analysis in detail. Laser treatment of Al/Al2O3 bi-phasic nanowires is a fast and easy method to fabricate nano- and microstructured Al2O3-surfaces for studying cell–surface interactions. It is our goal to develop a biocompatible Al2O3-surface which could be used as a coating material for medical implants exhibiting a cell selective response because of its specific physical landscape and especially because it promotes the adhesion of osteoblasts while minimizing the adhesion of fibroblasts.

Surface coating technology is an important way to improve the properties of orthodontic appliances, allowing for reduced friction, antibacterial properties, and enhanced corrosion resistance. It improves treatment efficiency, reduces side effects, and increases the safety and durability of orthodontic appliances. Existing functional coatings are prepared with suitable additional layers on the surface of the substrate to achieve the abovementioned modifications, and commonly used materials mainly include metal and metallic compound materials, carbon-based materials, polymers, and bioactive materials. In addition to single-use materials, metal-metal or metal-nonmetal materials can be combined. Methods of coating preparation include, but are not limited to, physical vapor deposition (PVD), chemical deposition, sol-gel dip coating, etc., with a variety of different conditions for preparing the coatings. In the reviewed studies, a wide variety of surface coatings were found to be effective. However, the present coating materials have not yet achieved a perfect combination of these three functions, and their safety and durability need further verification. This paper reviews and summarizes the effectiveness, advantages and disadvantages, and clinical perspectives of different coating materials for orthodontic appliances in terms of friction reduction, antibacterial properties, and enhanced corrosion resistance, and discusses more possibilities for follow-up studies as well as for clinical applications in detail.

Endowing conventional microcrystalline materials with nanometer-scale grains at the surfaces can offer enhanced mechanical properties, including improved wear, fatigue, and friction properties, while simultaneously enabling useful functionalizations with regard to biocompatibility, osseointegration, electrochemical performance, etc. To inherit such multifunctional properties from the surface nanograined state, existing approaches often use coatings that are created through an array of secondary processing techniques (e.g., physical or chemical vapor deposition, surface mechanical attrition treatment, etc.). Obviating the need for such surface processing, recent empirical evidence has demonstrated the introduction of integral surface nanograin structures on bulk materials as a result of severe plastic deformation during machining-based processes. Building on these observations, if empirically driven, process–structure mappings can be developed, it may be possible to engineer enhanced nanoscale surface microstructures directly using machining processes while simultaneously incorporating them within existing computer-numeric-controlled manufacturing systems. Toward this end, this article provides a statistical characterization of nanograined metals created by severe plastic deformation in machining-based processes that maps machining conditions to the resulting microstructure, namely, the mean grain size. A specialized designed experiments approach is used to hypothesize and test a linear mixed-effects model of two important machining parameters. Unlike standard analysis approaches, the statistical dependence between subsets of experimental grain size observations is accounted for and it is shown that ignoring this inherent dependence can yield misleading results for the mean response function. The statistical model is applied to pure copper specimens to identify the factors that most significantly contribute to variability in the mean grain size and is shown to accurately predict the mean grain size under a few scenarios.