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13 pages, 5656 KiB

Open AccessArticle

A Study of Low Young’s Modulus Ti–15Ta–15Nb Alloy Using TEM Analysis

by Huey-Er Lee, Ju-Hui Wu, Chih-Yeh Chao, Yen-Hao Chang, Je-Kang Du, Ker-Kong Chen and Huey-Ming Chen

Materials 2020, 13(24), 5694; https://doi.org/10.3390/ma13245694 - 14 Dec 2020

Cited by 4 | Viewed by 2110

Abstract

The microstructural characteristics and Young’s modulus of the as-cast Ti–15Ta–15Nb alloy are reported in this study. On the basis of the examined XRD and TEM results, the microstructure of the current alloy is essentially a mixture (α + β+ α′ + α″ + [...] Read more.

The microstructural characteristics and Young’s modulus of the as-cast Ti–15Ta–15Nb alloy are reported in this study. On the basis of the examined XRD and TEM results, the microstructure of the current alloy is essentially a mixture (α + β+ α′ + α″ + ω + H) phase. The new H phase has not previously been identified as a known phase in the Ti–Ta–Nb alloy system. On the basis of examination of the Kikuchi maps, the new H phase belongs to a tetragonal structural class with lattice parameters of a = b = 0.328 nm and c = 0.343 nm, denoting an optimal presentation of the atomic arrangement. The relationships of orientation between these phases would be {0001}_α//{110}_β//{

\bar{1}

2

\bar{1}

0}_ω//{10

\bar{1}

}_H and (01

\bar{1}

0)_α//(1

\bar{1}

2)_β//(

\bar{1}

010)_ω//(121)_H. Moreover, the Young’s modulus of the as-cast Ti–15Ta–15Nb alloy is approximately E = 80.2 ± 10.66 GPa. It is implied that the Young’s modulus can be decreased by the mixing of phases, especially with the presence of the H phase. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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22 pages, 12513 KiB

Open AccessArticle

Wear Morphology on the Surfaces of CoCrMo Unicompartmental Knee Joint Endoprostheses as Elements of Metal–Metal Friction Nodes

by Arkadiusz Szarek, Grzegorz Stradomski, Justyna Łukomska-Szarek, Dariusz Rydz, Wojciech Wolański and Kamil Joszko

Materials 2020, 13(12), 2689; https://doi.org/10.3390/ma13122689 - 12 Jun 2020

Cited by 7 | Viewed by 2793

Abstract

The article assesses the strength and structural parameters of load-bearing layers of metal biobearings made of CoCrMo alloy. The research material consisted of unicompartmental knee joint endoprostheses used in the human body, removed due to excessive wear. No patient participated in the examinations. [...] Read more.

The article assesses the strength and structural parameters of load-bearing layers of metal biobearings made of CoCrMo alloy. The research material consisted of unicompartmental knee joint endoprostheses used in the human body, removed due to excessive wear. No patient participated in the examinations. The endoprostheses used as research material underwent the liquidation procedures in the hospital, which has all necessary permissions and certifications to perform endoprosthetic procedures. Endoprostheses selected for the examinations had been used for 6 to 12 years at similar load conditions as declared by the patients, i.e., body weight of F = 835 N, declared activity expressed as the number of load cycles up to 100 thousand/year, and no artificial joint infections. To assess the homogeneity of the research material, the analysis of chemical composition using a Joel scanning electron microscope with EDS (Energy-dispersive X-ray spectroscopy) was made to exclude endoprostheses with various alloying additives. Microscopic examinations were performed using the Phenom XL microscope, while the wear surface was examined using a Keyence VHX-900F microscope. Several experimental tests were also carried out on load-bearing surfaces to assess changes in strength parameters of the base material after a known life cycle and load conditions. Material hardness using the Vickers method, yield point, critical value of stress intensity coefficient, and the coefficient of friction µ were evaluated. The examinations allowed for the systematization of wear in the knee and femoral components of unicompartmental hip endoprostheses. The statistical evaluation of the number and costs of hip joint replacement surgeries in Poland was also made. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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11 pages, 3017 KiB

Open AccessArticle

Mechanism of Fatigue Crack Growth in Biomedical Alloy Ti-27Nb

by Muhammad Amjad, Saeed Badshah, Amer Farhan Rafique, Muhammad Adil Khattak, Rafi Ullah Khan and Wail Ismail Abdullah Harasani

Materials 2020, 13(10), 2299; https://doi.org/10.3390/ma13102299 - 16 May 2020

Cited by 4 | Viewed by 3124

Abstract

Implants are widely used in the human body for the replacement of affected bones. Fatigue failure is one of the serious concerns for implants. Therefore, understanding of the underlying mechanism leading to fatigue failure is important for the longevity of biomaterial implants. In [...] Read more.

Implants are widely used in the human body for the replacement of affected bones. Fatigue failure is one of the serious concerns for implants. Therefore, understanding of the underlying mechanism leading to fatigue failure is important for the longevity of biomaterial implants. In this paper, the fracture toughness and fatigue crack growth of titanium alloy biomaterial Ti-27Nb has been experimentally investigated. The Ti-27Nb material is tested for fatigue crack growth in different environmental conditions representing the ambient and in vitro environments for 504 hours and 816 hours, respectively. Fractography of the tested specimen is conducted using Scanning Electron Microscope (SEM). The results of the fatigue crack growth propagation of the ambient and in vitro samples are similar in the Paris crack growth region. However, in the threshold region, the crack growth rate is higher for the Simulated Body Fluid (SBF) treated specimen. The fracture surface morphology of in vitro samples shows brittle fracture as compared to ambient specimens with significant plasticity and striations marks. It is proposed that a similar investigation may be conducted with specimens treated in SBF for prolonged periods to further ascertain the findings of this study. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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18 pages, 12062 KiB

Open AccessFeature PaperArticle

The Effect of Hot Working on the Mechanical Properties of High Strength Biomedical Ti-Nb-Ta-Zr-O Alloy

by Dalibor Preisler, Miloš Janeček, Petr Harcuba, Jan Džugan, Kristýna Halmešová, Jaroslav Málek, Anna Veverková and Josef Stráský

Materials 2019, 12(24), 4233; https://doi.org/10.3390/ma12244233 - 17 Dec 2019

Cited by 11 | Viewed by 3192

Abstract

Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, [...] Read more.

Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, the porosity, large grain size and chemical inhomogeneity reduce the fatigue performance below the limits required for utilization in the desired application. Two methods of hot working, die forging and hot rolling, were used for processing of this alloy. Microstructural evolution, tensile properties and fatigue performance of the hot worked material were investigated and compared to the cast material. Microstructural observations revealed that porosity is removed in all hot-worked conditions and the grain size is significantly reduced when the area reduction exceeds 70%. Static tensile properties were improved by both processing methods and ultimate tensile strength (UTS) of 1200 MPa was achieved. Fatigue results were more reproducible in the hot rolled material due to better microstructural homogeneity, but forging leads to an improved fatigue performance. Fatigue limit of 400 MPa was achieved in the die-forged condition after 70% of area reduction and in the hot rolled condition after 86% of area reduction. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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17 pages, 6893 KiB

Open AccessFeature PaperArticle

The Effect of Equal-Channel Angular Pressing on the Microstructure, the Mechanical and Corrosion Properties and the Anti-Tumor Activity of Magnesium Alloyed with Silver

by Yuri Estrin, Natalia Martynenko, Natalia Anisimova, Diana Temralieva, Mikhail Kiselevskiy, Vladimir Serebryany, Georgy Raab, Boris Straumal, Björn Wiese, Regine Willumeit-Römer and Sergey Dobatkin

Materials 2019, 12(23), 3832; https://doi.org/10.3390/ma12233832 - 21 Nov 2019

Cited by 22 | Viewed by 3252

Abstract

The effect of equal-channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, corrosion resistance and cytotoxicity of two magnesium-silver alloys, Mg-2.0%Ag and Mg-4.0%Ag, was studied. Their average grain size was found to be reduced to 3.2 ± 1.4 μm and 2.8 ± [...] Read more.

The effect of equal-channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, corrosion resistance and cytotoxicity of two magnesium-silver alloys, Mg-2.0%Ag and Mg-4.0%Ag, was studied. Their average grain size was found to be reduced to 3.2 ± 1.4 μm and 2.8 ± 1.3 μm, respectively. Despite the substantial grain refinement, a drop in the strength characteristics of the alloys was observed, which can be attributed to the formation of inclined basal texture. On a positive side, an increase in tensile ductility to ~34% for Mg-2.0%Ag and ~27% for Mg-4.0%Ag was observed. This effect can be associated with the activity of basal and prismatic slip induced by ECAP. One of the ECAP regimes tested gave rise to a drop in the corrosion resistance of both alloys. An interesting observation was a cytotoxic effect both alloys had on tumor cells in vitro. This effect was accompanied with the release of lactate dehydrogenase, an increase in oxidative stress, coupled with the induction of NO-ions and an increase in the content of such markers of apoptosis as Annexin V and Caspase 3/7. Differences in the chemical composition and the processing history-dependent microstructure of the alloys did not have any significant effect on the magnitude of their antiproliferative effect. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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18 pages, 6669 KiB

Open AccessArticle

The Fundamental Comparison of Zn–2Mg and Mg–4Y–3RE Alloys as a Perspective Biodegradable Materials

by Jiří Kubásek, Drahomír Dvorský, Jiří Šedý, Šárka Msallamová, Jitka Levorová, René Foltán and Dalibor Vojtěch

Materials 2019, 12(22), 3745; https://doi.org/10.3390/ma12223745 - 13 Nov 2019

Cited by 29 | Viewed by 3668

Abstract

Biodegradable materials are of interest for temporary medical implants like stents for restoring damaged blood vessels, plates, screws, nails for fixing fractured bones. In the present paper new biodegradable Zn–2Mg alloy prepared by conventional casting and hot extrusion was tested in in vitro [...] Read more.

Biodegradable materials are of interest for temporary medical implants like stents for restoring damaged blood vessels, plates, screws, nails for fixing fractured bones. In the present paper new biodegradable Zn–2Mg alloy prepared by conventional casting and hot extrusion was tested in in vitro and in vivo conditions. Structure characterization and mechanical properties in tension and compression have been evaluated. For in vivo tests, hemispherical implants were placed into a rat cranium. Visual observation of the living animals, an inspection of implant location and computed tomography CT imaging 12 weeks after implantation were performed. Extracted implants were studied using scanning electron microscopy (SEM) on perpendicular cuts through corrosion products. The behaviour of zinc alloy both in in vitro and in vivo conditions was compared with commercially used Mg-based alloy (Mg–4Y–3RE) prepared by conventional casting and hot extrusion. Both compressive and tensile yield strengths of Zn and Mg-based alloys were similar; however, the brittleness of Mg–4Y–3RE was lower. Zn and Mg-based implants have no adverse effects on the behaviour or physical condition of rats. Moreover, gas bubbles and the inflammatory reaction of the living tissue were not detected after the 12-week period. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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17 pages, 4248 KiB

Open AccessArticle

Mechanical Properties, Biodegradation, and Biocompatibility of Ultrafine Grained Magnesium Alloy WE43

by Sergey Dobatkin, Natalia Martynenko, Natalia Anisimova, Mikhail Kiselevskiy, Dmitriy Prosvirnin, Vladimir Terentiev, Nikita Yurchenko, Gennady Salishchev and Yuri Estrin

Materials 2019, 12(21), 3627; https://doi.org/10.3390/ma12213627 - 4 Nov 2019

Cited by 29 | Viewed by 3927

Abstract

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studied. The grain refinement down to 0.93 ± 0.29 µm and [...] Read more.

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studied. The grain refinement down to 0.93 ± 0.29 µm and the formation of Mg₄₁Nd₅ phase particles with an average size of 0.34 ± 0.21 µm were shown to raise the ultimate tensile strength to 300 MPa. Besides, MAD improved the ductility of the alloy, boosting the total elongation from 9% to 17.2%. An additional positive effect of MAD was an increase in the fatigue strength of the alloy from 90 to 165 MPa. The formation of the UFG structure also reduced the biodegradation rate of the alloy under both in vitro and in vivo conditions. The relative mass loss after six weeks of experiment was 83% and 19% in vitro and 46% and 7% in vivo for the initial and the deformed alloy, respectively. Accumulation of hydrogen and the formation of necrotic masses were observed after implantation of alloy specimens in both conditions. Despite these detrimental phenomena, the desired replacement of the implant and the surrounding cavity with new connective tissue was observed in the areas of implantation. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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16 pages, 8438 KiB

Open AccessFeature PaperArticle

Magnesium-Based Bioactive Composites Processed at Room Temperature

by Moara M. Castro, Debora R. Lopes, Renata B. Soares, Diogo M. M. dos Santos, Eduardo H. M. Nunes, Vanessa F. C. Lins, Pedro Henrique R. Pereira, Augusta Isaac, Terence G. Langdon and Roberto B. Figueiredo

Materials 2019, 12(16), 2609; https://doi.org/10.3390/ma12162609 - 16 Aug 2019

Cited by 14 | Viewed by 3099

Abstract

Hydroxyapatite and bioactive glass particles were added to pure magnesium and an AZ91 magnesium alloy and then consolidated into disc-shaped samples at room temperature using high-pressure torsion (HPT). The bioactive particles appeared well-dispersed in the metal matrix after multiple turns of HPT. Full [...] Read more.

Hydroxyapatite and bioactive glass particles were added to pure magnesium and an AZ91 magnesium alloy and then consolidated into disc-shaped samples at room temperature using high-pressure torsion (HPT). The bioactive particles appeared well-dispersed in the metal matrix after multiple turns of HPT. Full consolidation was attained using pure magnesium, but the center of the AZ91 disc failed to fully consolidate even after 50 turns. The magnesium-hydroxyapatite composite displayed an ultimate tensile strength above 150 MPa, high cell viability, and a decreasing rate of corrosion during immersion in Hank’s solution. The composites produced with bioactive glass particles exhibited the formation of calcium phosphate after 2 h of immersion in Hank’s solution and there was rapid corrosion in these materials. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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Review

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16 pages, 3937 KiB

Open AccessReview

Developing Nanostructured Ti Alloys for Innovative Implantable Medical Devices

by Ruslan Z. Valiev, Egor A. Prokofiev, Nikita A. Kazarinov, Georgy I. Raab, Timur B. Minasov and Josef Stráský

Materials 2020, 13(4), 967; https://doi.org/10.3390/ma13040967 - 21 Feb 2020

Cited by 39 | Viewed by 4129

Abstract

Recent years have witnessed much progress in medical device manufacturing and the needs of the medical industry urges modern nanomaterials science to develop novel approaches for improving the properties of existing biomaterials. One of the ways to enhance the material properties is their [...] Read more.

Recent years have witnessed much progress in medical device manufacturing and the needs of the medical industry urges modern nanomaterials science to develop novel approaches for improving the properties of existing biomaterials. One of the ways to enhance the material properties is their nanostructuring by using severe plastic deformation (SPD) techniques. For medical devices, such properties include increased strength and fatigue life, and this determines nanostructured Ti and Ti alloys to be an excellent choice for the engineering of implants with improved design for orthopedics and dentistry. Various reported studies conducted in this field enable the fabrication of medical devices with enhanced functionality. This paper reviews recent development in the field of nanostructured Ti-based materials and provides examples of the use of ultra-fine grained Ti alloys in medicine. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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