Biomedical Alloy Research Articles

Improving the Bio-Tribological Properties of Ti6Al4V Alloy via Combined Treatment of Femtosecond Laser Nitriding and Texturing

This paper presents a compound laser surface modification strategy to enhance the tribological performance of biomedical titanium alloys involving femtosecond laser nitriding and femtosecond laser texturing. First, high-repetition-rate femtosecond pulses (MHz) were used to melt the surface under a nitrogen atmosphere, forming a wear-resistant TiN coating. Subsequently, the TiN layer was ablated in air with low-repetition-rate femtosecond pulses (kHz) to create squared textures. The effects of the combined nitriding and texturing treatment on bio-tribological performance was investigated. Results show that compared with the untreated samples, the single femtosecond laser nitriding process increased the surface hardness from 336 HV to 1455 HV and significantly enhanced the wear resistance of titanium, with the wear loss decreasing from 9.07 mg to 3.41 mg. However, the friction coefficient increased from 0.388 to 0.655, which was attributed to the increased hardness, roughness within the wear scars, and the formation of hard debris. After combined treatment, the friction coefficient decreased to 0.408 under the optimal texture density of 65%. The mechanisms for the improvement in friction behavior are the reduction in contact area and the trapping of hard debris.

Studies on surface roughness and axial thrust force of drilled holes in Mg-Zn-Ca bio-medical alloy

Mg-Zn-Ca alloy is a promising candidate for orthopaedic implants such as bone plates and screws, as it has a similar mechanical strength and elastic modulus to bone, and it degrades in the body without causing toxicity or inflammation. Drilling studies are necessary to optimize the drilling process parameters, to evaluate the machinability and surface integrity of Mg-Zn-Ca alloy, and to ensure the effective and efficient drilling for various applications in the medical and engineering fields. The present experimental study emphasizes the influence of Ca content, biofriendly coolants and their combined effect with standard drill bits on the surface quality and axial thrust force in the drilling operation of Mg-Zn-Ca alloy. The drilling parameters such as cutting speed, feed rate, standard tools, bio-compatible coolants were optimized with respect to the amount of Ca in the Mg-Zn alloy. The axial thrust force and average surface roughness of drilled holes were considered as response of the experiments. The drilled surfaces were measured for average surface roughness in the transverse direction along the centre path of the drilled hole and a qualitative analysis was also carried out using advanced confocal microscope. The results revealed that the cutting speed among continuous factors significantly influenced the axial thrust force and average surface roughness. The effect of categorical factors was assessed using a regression based ranking method. The results of statistical analysis revealed that high speed steel, and vegetable oil offered improved surface quality, whereas the coconut oil showed low axial thrust force. The liquid nitrogen showed high value of axial thrust force and average surface roughness due to the brittleness induced by cryogenic coolant before drilling operation.

On the effect of energy input on microstructure evolution and mechanical properties of laser beam powder bed fusion processed Ti-27Nb-6Ta biomedical alloy

Additive manufacturing of pre-alloyed Ti-27Nb-6Ta powder by laser beam powder bed fusion (PBF-LB/M) employing a wide range of processing parameters is reported. An in-depth microstructure analysis along the whole process chain from powder feedstock material to additively manufactured bulk structures was conducted employing scanning electron microscopy (SEM) as well as X-ray and high-energy synchrotron diffraction. It is shown that near-fully dense parts (≥ 99.96%) with β+α’’ dual-phase microstructure and very homogenous element distribution are obtained in a large process window. In particular, a considerable influence of the energy input during PBF-LB/M on the solidification microstructure, i.e. phase composition and texture, is found. With increasing energy per unit area (EA) values both an increase in the volume fraction of the bcc β-phase and more pronounced texture components are seen. Furthermore, the mechanical behavior was evaluated under monotonic tensile loading. The PBF-LB/M processed Ti-27Nb-6Ta structures feature good mechanical properties with ultimate tensile strength (UTS) and strain to failure values of up to 768 MPa and 33.8 %, respectively. Due to the strong impact of the energy input during additive manufacturing on the microstructure evolution, however, a significant inverse strength-ductility behavior is observed. While UTS clearly decreases with increasing EA values, strain to failure increases at the same time. The underlying relationships between processing (energy input), microstructure and mechanical properties are explored and rationalized.

Design, preparation and properties of biomedical Ti-Nb quaternary alloys with high strength and low modulus: insights from first-principles calculations

In this paper, we designed and developed biomedical β-type Ti-Nb quaternary alloy materials with high strength and low modulus. Building upon the d-electron alloy design method and the valence electron concentration e/a method, we use a Python program and thermodynamic theoretical parameters to determine a Ti-Nb quaternary alloy with the characteristics of a single-phase solid solution. Subsequently, we engage in theoretical and experimental investigations on the low modulus alloys identified through first-principles calculations. The results show that both Ti7Nb6Zr1Al2 and Ti11Nb2Ta2Al1 maintain a single β phase before and after cold rolling, which is related to the strong electronic density of states of s and p orbitals at low energy levels in the crystal structure of the two alloys. Ti11Nb2Ta2Al1 has a strong charge distribution on the (001) crystal plane, which causes a large amount of internal stress under large deformation conditions to promote grain crushing and weaken the intensity of the (001)[1-10] texture in the ODF diagram of 2 = 45°. The cold-rolled Ti11Nb2Ta2Al1 exhibits better corrosion resistance and biocompatibility than the cold-rolled Ti7Nb6Zr1Al2, and the good biocompatibility is related to the strong covalent bond between Al and Ta that inhibits the diffusion of Al ions. 90% cold-rolled Ti11Nb2Ta2Al1 stands out as an exceptionally promising orthopedic implant material due to its high elastic allowable strain (ReH/E), good corrosion resistance and biocompatibility.

Developing novel Ti-Nb-Zr-Mo-Sn-O biomedical titanium alloys with high strength and low modulus through high-throughput experiments

Biomedical titanium alloys have been widely used as surgical implant materials, but traditional biomedical titanium alloys no longer meet practical needs, and there is an urgent need to develop new biomedical titanium alloys. In this study, the composition, microstructure, and mechanical properties of novel Ti-xNb-yZr-5Mo-6Sn-0.6O biomedical titanium alloys were investigated based on diffusion multiple high-throughput experiments. The results showed that although the microstructure of the alloys transitioned from β + α″ to β phase with the increase of Nb and Zr content, the β-stabilizing effect of Zr is weaker. The microhardness and elastic modulus of the alloys varied in the range of 2.7∼7.8GPa and 74.3∼130.2GPa, and depended strongly on the Nb content. In the Ti-xNb-yZr-5Mo-6Sn-0.6O system alloy, the Ti-7.8Nb-1.7Zr-5Mo-6Sn-0.6O alloy with the high hardness of 5.5 GPa and low elastic modulus of 74.3 GPa is a promising candidate for orthopedic implants. Moreover, this work indicates that high-throughput experiments are an effective method for rapidly developing high-performance biomedical titanium alloys.

Revealing the fundamental relationship between the properties and microstructures of biomedical TiZrTaNbMo high entropy alloy

The body-centered cubic high-entropy alloys are a promising candidate as implanting materials for biomedical areas, but their severe strength-ductility trade-off limits their application. Herein, we designed and prepared the biomedical TiZrTaNbMo HEAs with different atomic ratios by adjusting their elemental composition based on the theoretical calculation of negative mixing enthalpy and valence electron concentration. It was found that the (TiZr)47(TaNbMo)2 alloy has BCC and HCP mixing structure, and the (TiZr)42.5(TaNbMo)5 and the (TiZr)45(TaNbMo)3.33 have simple BCC structure. the yield strength (YS) and total tensile elongation of the (TiZr)42.5(TaNbMo)5, (TiZr)45(TaNbMo)3.33, (TiZr)47(TaNbMo)2 are 866 ± 28 MPa and 16.5 ± 1.1 %, 929 ± 13 MPa and 17.8 ± 1.2 %, 899 ± 6 MPa and 5.5 ± 0.1 %, respectively. The theoretical calculation shows that the high YS strength mainly comes from the solid solution strengthening effect, the high ductility can be explained by the negative mixing enthalpy induced by Mo element. In addition, the (TiZr)45(TaNbMo)3.33 alloy has better wear resistance and corrosion resistance than the commercially available Ti6Al4V. This study shed light on synthesizing the high entropy alloy with the desired comprehensive properties as biomedical implant materials.

Microstructure refinement, mechanical performances and degradability of biomedical Zn-2Cu alloy by ultrasonic melting and homogenization treatment

Zn alloys are deemed to be desired body implant materials because of their moderate degradation rate. In this paper, the microstructural evolution, mechanical performances, and degradability of Zn-2Cu alloy prepared by ultrasonic melt treatment (UMT) with different ultrasonic powers (0 W, 300 W, 600 W, and 900 W) were systematically studied. Under the condition of UMT, the coarse α-Zn grains of Zn-2Cu alloy were refined into fine equiaxed grains and the mean size was significantly decreased from 133.4 μm to 65.3 μm when the ultrasound power was enhanced. The precipitating CuZn5 phase was significantly refined from the coarse block into the spherical shape. Moreover, the fraction of the CuZn5 precipitates of the Zn-2Cu alloy was greatly reduced with the increase of ultrasonic power. Tensile tests showed that the ultimate tensile strength (UTS), yield strength (YS), and elongation (El) of Zn-2Cu alloy were remarkably enhanced to 203 MPa, 167 MPa, and 8.14 %, respectively, when the Zn-2Cu alloy melting was treated by 600 W power. It was found by electrochemical polarization test that the degradation rate of Zn-2Cu alloy treated by UMT with 0 W, 300 W, 600 W, and 900 W power in Hank’s solution was gradually decreased to 1.6312 mm/a, 1.3206 mm/a, 1.0992 mm/a, and 1.2832 mm/a, respectively. In addition, after the Zn-2Cu alloys were immersed in Hank’s solution for 30 days, the degradation rate of samples was summarized as 0 W alloy (0.472 mm/a) > 300 W alloy (0.436 mm/a) > 900 W alloy (0.412 mm/a) > 600 W alloy (0.398 mm/a). The studies verified that the UMT was a very valuable technology for preparing Zn-2Cu alloy, which can meet the requirement of mechanical properties and degradable rate as a promising implant material.

Enhancing the mechanical properties and corrosion resistance of biomedical Ti15Mo alloy with ultra-finer {332} twins via cyclic deformation

Mechanical properties, passivation behaviors and corrosion resistance of biomedical Ti15Mo alloy with ultra-finer twins were investigated. Cyclic deformation was conducted to activating more {332} twin variants via periodic changes of tension and compression. Microstructural refinement via numerous twins with the stable boundaries is different from other mechanisms, resulting in a higher hardness and maintaining the low elastic modulus after deformation and annealing. The results of electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy tests, revealed that twin boundaries are beneficial to enhancing passivation behaviors via forming a thicker oxide film in PBS solution. The alloy with ultra-finer {332} twins exhibit a better corrosion resistance due to a lower passivation current. The expected biomedical performance was obtained in the alloy after ±3 % amplitude cyclic deformation and 730 °C/7 min annealing, in contrast to the initial alloy with coarse grains, increasing 8.8 % of the hardness, decreasing 46 % of the corrosion current and maintaining the low elastic modulus.

Biodegradable magnesium based metal materials inhibit the growth of cervical cancer cells

Traditional chemotherapy drugs for cervical cancer often cause significant toxic side effects and drug resistance problems, highlighting the urgent need for more innovative and effective treatment strategies. Magnesium alloy is known to be degradable and biocompatible. The release of degradation products Mg2+, OH−, and H2 from magnesium alloy can alter the tumor microenvironment, providing potential anti-tumor properties. We explored the innovative use of magnesium alloy biomaterials in the treatment of cervical cancer, investigating how various concentrations of Mg2+ on the proliferation and cell death of cervical cancer cells. The results revealed that varying concentrations of Mg2+ significantly inhibited cervical cancer by arresting the cell cycle in the G0/G1 phase and inducing apoptosis in SiHa cells, effectively reducing tumor cell proliferation. In vivo experiments demonstrated that 20 mM Mg2+ group had the smallest tumor volume, exhibiting a potent inhibitory effect on the biological characteristics of cervical cancer. This enhances the therapeutic potential of this biomaterial as a local anti-tumor therapy and lays a theoretical foundation for the potential application of magnesium in the treatment of cervical cancer.

Experimental examination on electrochemical micro-machining of Mg–Li–Sr biomedical alloy: Application of ANOVA, Deng’s similarity, and ANFIS for effective modeling optimization

Experimental examination on electrochemical micro-machining of Mg–Li–Sr biomedical alloy: Application of ANOVA, Deng’s similarity, and ANFIS for effective modeling optimization

Design and characterization of novel Ti-8Mo-xFe-yCu alloys as implant materials: Evaluation of biocompatibility, mechanical properties, and antibacterial potential

Titanium and its alloys are highly desirable materials for biomedical metallic implants due to their superior specific strength, excellent corrosion resistance, and exceptional biocompatibility. Among these alloys, Ti6Al4V is widely used in practical biomedical applications because it offers an excellent combination of strength, fracture toughness, and corrosion resistance. However, recent research has revealed limitations in its biocompatibility attributed to the presence of toxic elements such as Al and V. In addition, it has been reported that Ti6Al4V is costly due to the addition of Vanadium and has the potential for post-implant inflammation. As a result, researchers have been investigating new biomedical beta-Ti alloys using biocompatible, affordable, and easily accessible beta-stabilizers like Mo, Fe, and Cu, to achieve similar performance as Ti6Al4V alloys. The present study aims to develop a novel biomedical alloy through the arc melting method, to obtain an implant material possessing low elastic moduli, biocompatibility, and antibacterial properties to mitigate the risk of post-implant inflammation. Microstructural analysis was conducted using microscopy and x-ray diffraction, while the mechanical properties were evaluated through micro vickers hardness testing machine and elastic moduli measurement utilizing the impulse excitation technique. Cytotoxicity assessment was performed using the (Cell Counting Kit-8) CCK-8 method, followed by an examination of the alloy's antibacterial properties using the point counting method. β-Ti single phase was obtained in this study with the addition of ≥1% Fe and ≥1% Cu. The Ti-8Mo-2Fe-2Cu alloy was found to have the lowest elastic moduli of 95 GPa. Electrochemical measurements show that the Ti-8Mo- xFe- yCu alloys have a lower corrosion current density of around 0.319–2.317 µA/cm2 compared to Ti6Al4V of 16.543 µA/cm2. The Ti-8Mo-1Fe-3Cu, Ti-8Mo-3Fe-1Cu, and Ti-8Mo-3Fe-3Cu alloys have comparable biocompatibility with Ti6Al4V with the viability of mesenchymal stem cells (MSCs) above 75% and have a positive antibacterial response. Ti-8Mo-3Fe-3Cu alloy demonstrates the most favorable blend of microstructure, mechanical attributes, corrosion resistance, cell viability, and antibacterial properties as an alternate biomaterial for implant applications.

Biodegradation, Antibacterial Performance, and Cytocompatibility of a Novel ZK30-Cu-Mn Biomedical Alloy Produced by Selective Laser Melting.

In the present study, an antibacterial biomedical magnesium (Mg) alloy with a low biodegradation rate was designed, and ZK30-0.2Cu-xMn (x = 0, 0.4, 0.8, 1.2, and 1.6 wt%) was produced by selective laser melting, which is a widely applied laser powder bed fusion additive manufacturing technology. Alloying with Mn evidently influenced the grain size, hardness, and biodegradation behavior. On the other hand, increasing Mn content to 0.8 wt% resulted in a decrease of biodegradation rate which is attributed to the decreased grain size and relatively protective surface layer of manganese oxide. Higher Mn contents increased the biodegradation rate attributed to the presence of the Mn-rich particles. Taken together, ZK30-0.2Cu-0.8Mn exhibited the lowest biodegradation rate, strong antibacterial performance, and good cytocompatibility.

Systematic characterization and enhanced corrosion resistance of novel β-type Ti-30Zr-5Mo biomedical alloys with halloysite nanotubes (HNTs) and zirconia (ZrO2)-reinforced polylactic acid (PLA) matrix coatings

This study investigates synthesis, the in-vitro corrosion resistance and adhesion performance of PLA-based composite coatings reinforced with halloysite nanotubes (HNT) and zirconia (ZrO2) on beta-type Ti-30Zr-5Mo biomedical alloys. The coatings were synthesized using the sol-gel method and characterized for their surface morphology, chemical composition, and electrochemical properties. SEM analysis revealed the presence of micropores and cracks, particularly in HNT and HNT/ZrO2 bilayer coatings. XPS and Raman spectroscopy confirmed the successful integration of HNT and ZrO2 into the PLA matrix. The potentiodynamic polarization scans and electrochemical impedance spectroscopy (EIS) showed enhanced corrosion resistance for coatings containing HNT and ZrO2, with the HNT/ZrO2 bilayer demonstrating the best performance. Contact angle measurements indicated hydrophilic properties, crucial for bioactive surfaces. Overall, the study demonstrates that HNT and ZrO2 reinforcements in PLA coatings significantly improve the corrosion resistance and bioactivity of Ti-30Zr-5Mo alloys, making them promising candidates for biomedical applications. Details are compared and discussed in the text.

Improving the phosphating process for Ca-P coating on ZK21 biomedical magnesium alloy

Improving the phosphating process for Ca-P coating on ZK21 biomedical magnesium alloy

Anti-friction and anti-infection properties on biomedical Ti3Zr2Sn3Mo25Nb alloy driven by high-precision cross-elliptical micro-texture and copper coating

A surface modification method was proposed to boost tribological properties of near β-type biomedical titanium alloy Ti3Zr2Sn3Mo25Nb (TLM) by synergistic application of micro-texture and copper coating. In calf serum, the friction coefficient on the TLM surface decreased by approximately 17 % when the micro-texture density was 15 %. Furthermore, the texture-free modified TLM surface exhibited reduced friction coefficients under various loads, with a maximum decrease of nearly 30 %. Additionally, the wear mass and wear rate of TLM surface were as low as 1.97 times and 2.34 times of commercial Ti6Al4V alloy when combining micro-texture with copper coating, respectively. The anti-friction mechanism can be attributed to enhanced load-bearing capacity due to micro-texture and the self-lubricating effect by copper coating. Importantly, introducing copper coating on micro-textured surface will catalyze protein denaturation to generate graphite-like carbon films during friction with an anti-friction property, meanwhile, exhibited significant antibacterial activity, with the antibacterial rate of 99.41 % and 94.70 % against Staphylococcus aureus and Escherichia coli, effectively improving postoperative infections.

Evaluation of the Tribocorrosion Behavior of Ti-6Al-4V Biomedical Alloy in Simulated Oral Environments

Evaluation of the Tribocorrosion Behavior of Ti-6Al-4V Biomedical Alloy in Simulated Oral Environments

A novel titanium alloy for load-bearing biomedical implants: Evaluating the antibacterial and biocompatibility of Ti536 produced via electron beam powder bed fusion additive manufacturing process

Additive manufacturing (AM) of Ti-based biomedical implants is a pivotal research topic because of its ability to produce implants with complicated geometries. Despite desirable mechanical properties and biocompatibility of Ti alloys, one major drawback is their lack of inherent antibacterial properties, increasing the risk of postoperative infections. Hence, this research focuses on the Ti536 (Ti5Al3V6Cu) alloy, developed through Electron Beam Powder Bed Fusion (EB-PBF), exploring bio-corrosion, antibacterial features, and cell biocompatibility. The microstructural characterization revealed grain refinement and the formation of Ti2Cu precipitates with different morphologies and sizes in the Ti matrix. Electrochemical tests showed that Cu content minimally influenced the corrosion current density, while it slightly affected the stability, defect density, and chemical composition of the passive film. According to the findings, the Ti536 alloy demonstrated enhanced antibacterial properties without compromising its cell biocompatibility and corrosion behavior, thanks to Ti2Cu precipitates. This can be attributed to both the release of Cu ions and the Ti2Cu precipitates. The current study suggests that the EB-PBF fabricated Ti536 sample is well-suited for use in load-bearing applications within the medical industry. This research also offers an alloy design roadmap for novel biomedical Ti-based alloys with superior biological performance using AM methods.

Innovative design of heterogeneous structures in Cu-containing titanium alloys to enhance mechanical properties, abrasion resistance, and antibacterial performance

How to precisely modulate the morphology and distribution of precipitated phases to have long-term antibacterial activity and outstanding strength-ductility has slowed the overall development and engineering applications of Cu-bearing biomedical titanium alloys. For the first time, the electron beam powder bed fusion (EBPBF) was employed to design titanium alloys with a completely solid solution, and containing fine Ti2Cu precipitates in both uniform and layered structures. The mechanical properties of the designed alloy with the layered (α-Ti and Ti2Cu) structure are superior to the other structures, especially with an outstanding compressive yield strength of 1221.9 MPa. Simultaneously, the wear resistance of the heterogeneous structures containing Ti2Cu precipitates was significantly improved, with a specific wear rate only half of that of the EBPBF-fabricated Ti6Al4V alloy. The compact arrangement of Ti2Cu phases created a large number of interfaces conducive to the formation of corrosion channels, which provided the capacity of continuous Cu2+ release. This work comprehensively analyzes the effects of heterogeneous structures on enhancing the sustained antibacterial capacity and optimizing the mechanical properties of a Cu-containing titanium alloy, laying a good foundation for their application in clinical and implantable devices.

Effects of Dynamic Flow Rates on the In Vitro Bio-Corrosion Behavior of Zn-Cu Alloy

In the complicated real physiological environment in vivo, body fluids and blood are constantly replenished and move dynamically, and therefore, the dynamic impacts of bodily fluids and blood need to be considered in the evaluation of biodegradable materials. However, little research has been conducted on the impact of dynamic flowing circumstances on the corrosion characteristics of zinc-based alloys, particularly at high flow rates. The effects of various flow rates on the bio-corrosion behavior of the Zn-Cu alloy are thoroughly explored in this study. A model is developed using finite element analysis to investigate the impacts of flow rates and fluid-induced shear stress. The results reveal that the corrosion process of the Zn-Cu alloy is significantly accelerated by a higher flow rate, and a large fluid-induced shear stress caused by the boundary effect is found to promote corrosion. Furthermore, the empirical power function between the average flare rates in Hank’s solution and the corrosion rates of the Zn-Cu alloy is established by numerical simulation. The results provide insightful theoretical and experimental guidance to improve and evaluate the efficacy and lifespan of biomedical zinc-based alloy implants.

Effects of Zr and Hf on superelasticity, shape memory effect and microstructure of β-type (Ti–Zr–Hf)–Nb–Sn multi-principal element alloys with low magnetic susceptibility

(Ti–Zr–Hf)(97−x)–xNb–3Sn (Ti:(Zr + Hf) = 1:1) alloys were designed for biomedical superelastic alloys with magnetic resonance imaging (MRI) compatibility. The effects of Zr and Hf on constituent phases, superelasticity, shape memory effect and magnetic susceptibility were clarified. The specific Nb content for superelasticity and shape memory effect was also explored. It was found that the (Ti–Zr)–6.5Nb–3Sn alloy exhibited a superelastic recovery strain of 5.2 % with lower magnetic susceptibility compared to conventional Ti–Ni and Ti–Nb alloys. The magnetic susceptibility decreased with increasing Hf content. The (Ti–Hf)–9Nb–3Sn alloy showed a superelastic recovery strain of 0.9 % and very low magnetic susceptibility less than half of that of the conventional alloys. Based on the lattice parameters of these alloys, it was found that these alloys exhibited larger transformation lattice strain between a β phase and an α” phase than those of the Ti–Nb alloys, suggesting high potential to exhibit a large superelastic recovery strain. According to orientation analyses of constituting grains, the larger superelastic recovery strain in the (Ti–Zr)–6.5Nb–3Sn alloy than that of the (Ti–Hf)–9Nb–3Sn alloy is considered to be caused by a strong recrystallization texture of {001}β <110>β. By optimization of heat-treatment temperature, superelastic recovery strain of 3.6 % was achieved in the (Ti–0.5Zr–0.5Hf)–7.5Nb–3Sn alloy.