Alloys For Biomedical Applications Research Articles

Surface electropulsing-induced texture evolution in electron beam melted Ti-6Al-4V alloy for biomedical application

Surface electropulsing treatment has been demonstrated to significantly improve the surface strength of electron beam melted (EBM) Ti-6Al-4V alloy. However, further investigation is needed to understand the effect of this treatment on the surface texture of the alloy, as the texture of Ti alloy plays a crucial role in its corrosion performance. In this study, we explored the changes in texture induced by surface electropulsing in EBM Ti-6Al-4V alloy using electron backscattered diffraction (EBSD) and micro-region X-ray diffraction (Micro-XRD). The results revealed that surface electropulsing created a 〈0001〉α′//transverse direction (TD) texture on the alloy surface, and the intensity of this texture remained unaffected with varying electropulsing time (180–240 ms). Additionally, this treatment led to the formation of long curved martensite laths that could cross the small angle prior-β grain boundaries. The finite element method (FEM) was employed to aid in the analysis of the texture evolution mechanism. The results revealed that the most rapid cooling rate occurred perpendicular to the contact surface with the copper electrode, along the building direction (BD). When the (0001) plane aligned parallel to the direction of the fastest cooling rate, it promoted the growth of martensite, leading to an increased production of martensite with the (0001) plane parallel to the BD direction and generating the 〈0001〉α′//TD texture. Therefore, by controlling the position of the copper electrode during surface electropulsing treatment, it is possible to manipulate the orientation of the (0001) plane of most α′ laths. This suggests that surface electropulsing treatment holds potential for application in other Ti alloys to enhance strength and optimize texture for biomedical applications.

Diopside/graphene-oxide nanocomposite coatings on AZ31 Mg alloy for biomedical applications: Surface characteristics, corrosion, and biocompatibility properties

Surface functionalization of magnesium (Mg)-based alloys with coatings, represents a promising approach to improve the biocompatibility and corrosion resistance of these biodegradable materials for bone tissue engineering. In this study, electrophoretic deposition (EPD) was employed to apply diopside-graphene oxide (Dio/xGO) coatings at different GO concentrations (x= 0, 0.03, 0.06, and 0.12 g/L) onto AZ31 alloy. The study aimed to compare the surface characteristics, corrosion resistance, bioactivity, antibacterial property, and cytocompatibility of these coatings with the uncoated substrate. Diopside (CaMgSi2O6) powder was synthesized using the sol-gel method. FESEM imaging revealed that Dio/0.06GO nanocomposite coating exhibited a more compact morphology compared to the other ones. AFM studies indicated an increase in surface roughness with higher GO concentration, with a Sa=293.80 ± 23.75 nm measured in the Dio/0.12GO sample. A similar trend was observed in the coatings' wettability. The Dio/0.06GO coating exhibited the highest corrosion resistance, with a corrosion current density (icorr) 91.5% lower than the uncoated Mg alloy. Furthermore, apatite deposits with the highest Ca/P atomic ratio (1.61) formed on this coating after seven days of immersion in simulated body fluid (SBF), indicating its superior bioactivity compared to the other ones. Results from the antibacterial activity test showed that GO, particularly at higher concentrations, exhibited bactericidal effect against E. coli and S. aureus. In vitro cellular studies indicated that although Dio/0.12GO coating displayed the most favorable MCT3T-E1 osteoblast cellular adhesion, the highest cell viability (92.17 ± 1.2%) was associated with the Dio/0.6GO deposits. In conclusion, Dio/GO nanocomposite coatings showed the potential to improve corrosion resistance and biological properties in Mg alloy orthopedic applications.

Effect of medium renewal mode on the degradation behavior of Mg alloys for biomedical applications during the long-term in vitro test

To build a suitable corrosion environment for testing the degradation behavior of magnesium alloy in vitro, the medium and test environment are constantly optimized. However, the applicability of medium renewal mode is still vague. In this study, based on three representative test protocols, the influence of the specific ratio of media volume to surface area and the disposable medium real-time renewal mode (flow-through) on Mg corrosion were investigated. It is found that in flow-through medium renewal mode, the composition of the medium is maintained quasi-constant which is essential for corrosion tests. The selection suggestion on medium renewal mode was also proposed. This work is beneficial for ultimately establishing the representative in vitro testing protocols for Mg bioabsorbable materials.

Characterization of Tannic Acid-Coated AZ31 Mg Alloy for Biomedical Application and Comparison with AZ91.

Magnesium alloys are promising materials for bioresorbable implants that will improve patient life and reduce healthcare costs. However, their clinical use is prevented by the rapid degradation and corrosion of magnesium, which leads to a fast loss of mechanical strength and the formation of by-products that can trigger tissue inflammation. Here, a tannic acid coating is proposed to control the degradation of AZ31 and AZ91 alloys, starting from a previous study by the authors on AZ91. The coatings on the two materials were characterized both by the chemical (EDS, FTIR, XPS) and the morphological (SEM, confocal profilometry) point of view. Static degradation tests in PBS and electrochemical measurements in different solutions showed that the protective performances of the tannic acid coatings are strongly affected by the presence of cracks. The presence of fractures in the protective layer generates galvanic couples between the coating scales and the metal, worsening the corrosion resistance. Although degradation control was not achieved, useful insights on the degradation mechanisms of coated Mg surfaces were obtained, as well as key points for future studies: it resulted that the absence of cracks in protective coatings is of uttermost importance for novel biodegradable implants with proper degradation kinetics.

Investigation of the Chemical Composition, Microstructure, Density, Microhardness, and Elastic Modulus of the New β Ti-50Nb-xMo Alloys for Biomedical Applications.

β-type titanium alloys with a body-centered cubic structure are highly useful in orthopedics due to their low elastic modulus, lower than other commonly used alloys such as stainless steel and Co-Cr alloys. The formation of the β phase in titanium alloys is achieved through β-stabilizing elements such as Nb, Mo, and Ta. To produce new β alloys with a low modulus of elasticity, this work aimed to produce our alloy system for biomedical applications (Ti-50Nb-Mo). The alloys were produced by arc-melting and have the following compositions Ti-50Nb-xMo (x = 0, 3, 5, 7, and 12 wt% Mo). The alloys were characterized by density, X-ray diffraction, scanning electron microscopy, microhardness, and elastic modulus. It is worth highlighting that this new set of alloys of the Ti-50Nb-Mo system produced in this study is unprecedented; due to this, there needs to be a report in the literature on the production and structural characterization, hardness, and elastic modulus analyses. The microstructure of the alloys has an exclusively β phase (with bcc crystalline structure). The results show that adding molybdenum considerably increased the microhardness and decreased the elastic modulus, with values around 80 GPa, below the metallic materials used commercially for this type of application. From the produced alloys, Ti-50Nb-12Mo is highlighted due to its lower elastic modulus.

Heat Treatment Protocol for Additively Manufactured Nitinol Shape Memory Alloys in Biomedical Applications

Heat Treatment Protocol for Additively Manufactured Nitinol Shape Memory Alloys in Biomedical Applications

Effect of Heat Treatment Conditions on the Electrochemical Capability and Mechanical Properties of Titanium Grade V Alloy for Biomedical Applications

This research aimed to investigate the sustainability of grade V Titanium alloy (Ti-6Al-4V) in NaCl, as well as its mechanical properties for biomedical applications. Improving titanium alloys is critical for producing alloys with minimal side effects. The impacts of structure, indentation test, corrosion resistance, and wear resistance of six titanium alloys after aging were explored in this work. The heat treatment was carried out in a tube furnace with an inert gas, commencing at ambient temperature and progressing to a high temperature of 955°C. For 10 minutes, air and water were used to cool the sample. The samples were then heated to a continuous temperature tempering at 525°c in three steps for both air(A) and water(W) cooled samples 2, 3, and 4 hours. The microstructure was examined using an optical microscope, the corrosion rate was calculated using a potentiostat, hardness was estimated using the Rockwell B scale, and wear resistance was determined using a universal wear tester. It was observed that the water-quenched samples performed better than the air-cooled samples in terms of characteristics. Above all, the dwelling period during the aging process has a greater influence on the material’s characteristics.

Microstructure and Wear Behavior of Heat-Treated Mg-1Zn-1Ca Alloy for Biomedical Applications.

The microstructure and wear properties of a Mg-1wt.% Zn-1wt.% Ca (ZX11) alloy with different heat treatments have been investigated. The ZX11 alloy was tested in the as-cast state and after different heat treatment conditions: solution-treated (at 450 °C for 24 h), peak-aged (solution-treated + aged at 180 °C for 3 h), and over-aged (solution-treated + aged at 180 °C for 24 h). The microstructure of the as-cast sample showed a continuous intermetallic phase at the grain boundaries, while the heat-treated samples exhibited discrete precipitated particles within the grains. To evaluate the wear behavior, the samples were tested using a pin-on-disc configuration, where the wear rates and friction coefficients were measured at different loads and sliding speeds. An AZ31 magnesium alloy was used as the counterbody. The worn surfaces and the wear debris were studied to identify the main wear mechanisms corresponding to each test condition. The results indicated the presence of abrasion, oxidation, and adhesive wear mechanisms in all testing conditions. In the as-cast state, delamination and plastic deformation were the dominant wear mechanisms, while they were less relevant in the heat-treated conditions. The peak-aged samples exhibited the lowest wear rates, suggesting that modifying the distribution of intermetallic precipitates contributed to enhancing the wear resistance of the alloy.

Effect of milling time on structural, physical and tribological behavior of a newly developed Ti-Nb-Zr alloy for biomedical applications

Titanium (Ti)-based alloys with only a β-phase have attracted academic and industrial interest for orthopedic application, due to their close properties to those of tissues. The current study aims to investigate the effect of milling time (2 h, 6 h, 12 h and 18 h) on the nanostructured ternary alloy Ti-25Nb-25Zr prepared by high energy milling, on its structural, physical and tribological behaviors. The alloys’ characteristics such as relative density/porosity, surface roughness, were evaluated using XRD, SEM, surface profilometry, and microdurometer, respectively. The tribological characterization was done using an oscillating tribometer under wet conditions, simulating the human body environment. Results showed that the crystallite and mean pore size reduced with increasing milling time, with the smallest values of 26 nm and 40 µm, respectively after 18 h. Structural characterization shows that the amount of the β-Ti phase increased with increasing milling time, resulting in spherical morphology and texturing of the synthesized alloys. The milled alloys' structural evolution and morphological changes were sensitive to their milling times. Also, the relative density, Young’s modulus and hardness, increased due to grain size decreased with increasing milling time. Tribological results showed that the effect of milling has a significant effect on both nanomaterial formation and friction-wear behavior of the alloys. The results showed that, friction coefficient and wear rate significantly decreased due to the increased formation of protective films such as TiO2, Nb2O5 and ZrO2 phases. The wear mechanism of the Ti-25Zr-25Nb system was dominated by abrasion wear accompanied by adhesion wear.

Effect of low and high temperature ECAP modes on the microstructure, mechanical properties and functional fatigue behavior of Ti-Zr-Nb alloy for biomedical applications

A Ti-18Zr-15Nb (at%) shape memory alloy was subjected to a high-temperature thermomechanical treatment (HTMT) combining an equal channel angular pressing (ECAP) at 500 °C for n = 4–8 passes and a short-time post-deformation annealing (PDA) at 600 °C. The phase composition, microstructure, texture, mechanical and functional properties were studied. The functional fatigue behavior observed in this study was compared to that resulted from the reference low-temperature thermomechanical treatment (LTMT) by ECAP at 200 °C for 3 passes + PDA (600 °C for 5 min). The ECAP at 500 °C (n = 4) led to the formation of a highly deformed, dynamically polygonised substructure of β-phase with a crystallographic texture close to the [101] direction. In this state, the alloy exhibited an excellent combination of the static functional and mechanical properties: a relatively high strength (UTS = 670 MPa), a sufficient ductility (δ = 13.3 %), a low Young’s modulus (E < 40 GPa), and a high superelastic recovery strain (εrsemax= 3.1 %). An increase in the number of passes during ECAP to n = 8 led to a greater substructural hardening of the material, grain/subgrain refinement, and the release of α-phase. This significantly increased the alloy strength (UTS = 897 MPa), but reduced its ductility (δ = 5.9 %) and suppressed martensitic transformation. The alloy after both the HTMT (ECAP at 500 °C, n = 4) and TMT (ECAP at 200 °C, n = 3) processes exhibited an equally excellent functional fatigue resistance accompanied by a superior superelastic behavior with small accumulated strains. However, the HTMT process appears to be more technologically advanced, as it eliminates the need for PDA and reduces the risks of specimen cracking during processing.

Effect of Fe content on physical, tribological and photocatalytical properties of Ti-6Al-xFe alloys for biomedical applications

The aim of the current study is to evaluate the effect of iron content (0, 2, 4, 6 and 10 wt%) on the structural, tribological and photocatalytical properties of a nanostructured ternary alloy Ti-6Al-XFe, prepared by high energy milling. The alloys’ characteristics such as lattice parameters, powder morphologies, surface roughness, relative density/porosity, and microhardness, were evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), surface profilometry, porosimeter and micro durometer, respectively. The W-H method was utilized to determine the crystallite size. Micro strain was also calculated, which is produced in the lattice due to the diffusion of iron atoms. The photocatalytical characterization was conducted by measuring their absorbance as a function of time using spectrophotometer of visible and ultraviolet light in the wavelength range of 500–800 nm. The tribological characterization was performed using an oscillating tribometer under wet conditions, simulating the human body environment using Phosphate Buffered Saline (PBS) solution with neutral pH 7.4, under different applied loads of 2, 6 and 10 N, respectively. Results showed that the addition of Fe has a significant effect on the structural properties of the developed alloys. The lattice parameter (aα) decreased with increasing Fe content from 2.9493 Å (0 wt% Fe) to 2.9491 Å (10 wt% Fe), while the average grain size increased considerably from 6.965 nm (0 wt% Fe) to 44.42 nm (10 wt% Fe). The wear test results showed that, friction coefficient and wear rate considerably decreased due to the formation of protective films such as TiO2. The photocatalytical characterization showed that, the degradation of methylene blue (MB) increased with increasing Fe content. The Ti-6Al-4Fe -catalyst gave the best degree of degradation of 90.76% within 60 min, which meant that the decolorization process could be operated rapidly at a relatively low cost without UV irradiation.

Synergistic coating strategy combining photodynamic and photothermal properties along with reinforcing corrosion protection fabricated on magnesium alloys

Postoperative infections of bone implants and loss of mechanical strength due to the corrosion are two major obstacles in the pathway for the magnesium alloys applications in biomedical region. To resolve above issues, a novel hybrid coating, MAO/EPR/Gel, is prepared on AZ31B magnesium alloys, in which the photodynamic therapy (PDT) and photothermal therapy (PTT) agents are combined together to form Er@PDA-RB and they are inserted in the micropores of micro-arc oxidation (MAO) coating rather than doping in it. The gelatin is utilized to prevent the leaking of Er@PDA-RB and it would be decomposed spontaneously in the human body. The |Z|0.01Hz of MAO/EPR and MAO/EPR/Gel are 4.35 × 104 Ω cm2 and 6.99 × 104 Ω cm2, which is much larger than that of MAO coating and bare AZ31B Mg alloy with the values of 3.70 × 104 Ω cm2 and 1.50 × 103 Ω cm2, respectively. The antibacterial ratio for E. coli reaches 93.9% under 980nm near-infrared (NIR) irradiation within 60min. Moreover, the MAO/EPR/Gel coating displays the excellent cytocompatibility with the HL-7702 cell viability > 75% with or without 980nm NIR irradiation. This multifunctional integrated coating accomplishes both PDT and PTT functions with only one NIR irradiation without sacrificing the anti-corrosion feature, which exhibits a promising application for magnesium alloys in biomedical applications.

Micro-arc oxidation (MAO) and its potential for improving the performance of titanium implants in biomedical applications.

Titanium (Ti) and its alloys have good biocompatibility, mechanical properties and corrosion resistance, making them attractive for biomedical applications. However, their biological inertness and lack of antimicrobial properties may compromise the success of implants. In this review, the potential of micro-arc oxidation (MAO) technology to create bioactive coatings on Ti implants is discussed. The review covers the following aspects: 1) different factors, such as electrolyte, voltage and current, affect the properties of MAO coatings; 2) MAO coatings affect biocompatibility, including cytocompatibility, hemocompatibility, angiogenic activity, corrosion resistance, osteogenic activity and osseointegration; 3) antibacterial properties can be achieved by adding copper (Cu), silver (Ag), zinc (Zn) and other elements to achieve antimicrobial properties; and 4) MAO can be combined with other physical and chemical techniques to enhance the performance of MAO coatings. It is concluded that MAO coatings offer new opportunities for improving the use of Ti and its alloys in biomedical applications, and some suggestions for future research are provided.

Investigation of the nuclear radiation parameters of some Ti alloys for biomedical applications

This study investigates the nuclear radiation parameters of selected Ti alloys with potential biomedical applications. The compatibility with nuclear radiation is essential for these alloys in biomedical applications. To understand the nuclear radiation compatibility for this selected alloy, the gamma rays, neutrons, and charged particle interaction parameters were estimated using EpiXS, NGCal, ESTAR, and SRIM. The gamma rays, neutrons, and charged particle interaction parameters of selected Ti alloys relative to the cortical bone were studied. The Zeff of selected alloys relative to the cortical bone reaches unity in the lower photon energy region. Similar values of energy absorption buildup factor for selected alloys and cortical bone when the gamma energy region lies between 200 keV and 3 MeV. For neutron interaction at incident energy of thermal neutron at 25.4 meV and fast neutron 4 MeV, significant differences exist between selected alloys and cortical bone. From the estimated data, it is observed that among selected alloys, Ti-6Al-4V and Ti-6Al-4V-2.5Cu are comparable with cortical bone in terms of gamma rays and charged particle interactions. The results indicate that Ti-6Al-4V and Ti-6Al-4V-2.5Cu are the most suitable alloys for biomedical applications such as knee, hip, and elbow joints.

Laser textured Ti-6Al-7Nb alloy for biomedical applications: An investigation of texturing parameters on surface properties.

Surface texturing with a laser beam is an effective method for engraving on the surface of biomaterials. The four laser texturing parameters (scan speed, frequency, fill spacing, and pulse width) having five different values were associated with five different scanning strategies (scan direction), and a total of 25 texturing conditions were tested on the Ti-6Al-7Nb alloy surface. The surface roughness and wettability of the textures created with a 20 W nanosecond fiber laser with a wavelength of 1064 nm on the surface of Ti-6Al-7Nb biocompatible alloy were investigated. Laser texturing parameters were analyzed according to the lowest surface roughness and a hydrophilic surface by creating L25 orthogonal arrays. The surface roughness values ranged between 2 and 26 µm. The lowest surface roughness with a value of 2.21 µm was achieved when the texture was processed with a frequency of 150 kHz, a fill spacing of 0.02 mm, a scan speed of 800 mm/s, a pulse width of 250 ns, and a cross-hatch strategy of 0°/90°. Considering the wettability test results, it was revealed that most of the textured surfaces have super hydrophilic and hydrophilic characteristics except the surface with a contact angle of 92.93°. The relevant surface was textured with 75 kHz frequency, 1000 mm/s scan speed, 0.05 mm fill spacing, 200 ns pulse width, and 45°/-45° cross-hatch strategy.

A review on Wire-EDM of bio titanium

Nonconventional machining technologies have been found viable to manufacture various products from a wide range of engineering materials. Wire electric discharge machining (WEDM), also known as Wire-EDM, is one of the important thermal type nonconventional machining technologies. Wire-EDM is being preferably used by manufacturers to produce biomedical devices including bio and dental implants. This paper presents an overview of capabilities of wire-EDM type nonconventional machining technology for the precise machining of titanium and its alloys for biomedical applications. It reviews the important research work conducted on machining titanium alloys by wire electrical discharge machining (WEDM). Their findings and achievements are discussed to encourage further research and development in the biomaterial machining area.

COMPARISON AND PERFORMANCE OF α, α+β AND β TITANIUM ALLOYS FOR BIOMEDICAL APPLICATIONS

As implant materials, titanium and its alloys have been extensively utilized because of their exceptional mechanical properties and biocompatibility. Despite this, corporations and researchers alike have kept up their aggressive pursuit of better alloys since there are still issues that require immediate attention. One of these causes a problem with stress shielding as a noticeable variation in the elastic modulus of the implant material. Ti alloys release harmful ions after extended usage. The poor bioactivity of the Ti alloy surface slows the healing process. In order to address these problems, additional research has concentrated on developing Ti alloys for the 21st century that contain a more suitable phase and change the surface of the alloy from inherently bioinert to bioactive. This study assesses the knowledge presently existing on the biological, chemical, mechanical, and electrochemical characteristics of important [Formula: see text]-Ti alloys created in recent years with the objective to provide scientific justification for using [Formula: see text]-titanium-based alloys as a substitute for cpTi. Dental implants might be made using [Formula: see text]-Ti alloys as an alternative. The enhanced alloy qualities, which include a lower modulus of elasticity, improved strength, suitable biocompatibility, and good abrasion and excellent resistance to corrosion, offer the essential proof. Additionally, structural, chemical, and thermomechanical modifications to [Formula: see text]-Ti alloys allow for the production of materials that may be tailored to the needs of unique instances for clinical practises. By researching the paper, the performance and attributes of [Formula: see text]-titanium alloy are compared to those of other forms of titanium alloy, such as [Formula: see text] titanium alloys. To support their usage as cpTi substitutes, in vivo studies are required to assess new [Formula: see text]-titanium alloys.

Microstructure and properties of as-cast Zr-2.5Nb-1X (X = Ru, Mo, Ta and Si) alloys for biomedical application

Microstructure and properties of as-cast Zr-2.5Nb-1X (X = Ru, Mo, Ta and Si) alloys for biomedical application

The inhibition effect of etidronate on degradation behavior of Mg–Zn–Y-Nd-Zr alloy

The control of corrosion behavior of Mg alloys for biomedical applications is a research hotspot in the field of biodegradable metallic implant materials. In recent years, the employment of corrosion inhibitors for regulating the corrosion behavior of Mg alloys has attracted attention. In this work, a promising corrosion inhibitor for Mg alloys, Etidronate (ETN), was selected from the drugs for the treatment of osteoporosis, and its effect on the corrosion behavior of Mg–Zn–Y-Nd-Zr (ZE21C Mg alloy) in simulated body fluids was systematically studied. The results show that ETN not only reduces the corrosion rate of the alloy, but also significantly weakens its tendency of localized corrosion, which is beneficial for improving the service reliability of Mg alloy for orthopedic application. This study provides an idea for corrosion control of biodegradable Mg alloys and is of great significance for promoting their development and applications.

Phase-field modeling of pitting and mechanically-assisted corrosion of Mg alloys for biomedical applications.

A phase-field model is developed to simulate the corrosion of Mg alloys in body fluids. The model incorporates both Mg dissolution and the transport of Mg ions in solution, naturally predicting the transition from activation-controlled to diffusion-controlled bio-corrosion. In addition to uniform corrosion, the presented framework captures pitting corrosion and accounts for the synergistic effect of aggressive environments and mechanical loading in accelerating corrosion kinetics. The model applies to arbitrary 2D and 3D geometries with no special treatment for the evolution of the corrosion front, which is described using a diffuse interface approach. Experiments are conducted to validate the model and a good agreement is attained against in vitro measurements on Mg wires. The potential of the model to capture mechano-chemical effects during corrosion is demonstrated in case studies considering Mg wires in tension and bioabsorbable coronary Mg stents subjected to mechanical loading. The proposed methodology can be used to assess the in vitro and in vivo service life of Mg-based biomedical devices and optimize the design taking into account the effect of mechanical deformation on the corrosion rate. The model has the potential to advocate further development of Mg alloys as a biodegradable implant material for biomedical applications. STATEMENT OF SIGNIFICANCE: A physically-based model is developed to simulate the corrosion of bioabsorbable metals in environments that resemble biological fluids. The model captures pitting corrosion and incorporates the role of mechanical fields in enhancing the corrosion of bioabsorbable metals. Model predictions are validated against dedicated in vitro corrosion experiments on Mg wires. The potential of the model to capture mechano-chemical effects is demonstrated in representative examples. The simulations show that the presence of mechanical fields leads to the formation of cracks accelerating the failure of Mg wires, whereas pitting severely compromises the structural integrity of coronary Mg stents. This work extends phase-field modeling to bioengineering and provides a mechanistic tool for assessing the service life of bioabsorbable metallic biomedical devices.