bluuebunny/crossref_metadata_2025 huggingface dataset:
Empirical Relationships for the Impact of Nb and C Content on the Mechanical Properties of Hot Rolled Microalloyed Steels
Authors: Verbeken Kim , Vervynckt Stephanie , Thibaux Philippe , Houbaert Yvan
Published: January 2012

There currently is a strong interest in using ‘as-hot rolled’ steels instead of ‘heat treated’ steels within the field of microalloyed steels with superior strength and improved ductility. However, mechanical and microstructural characterization of these steels is less elaborated. The present work is an effort in that direction, focusing on the evaluation of the impact of a variable Nb and C content on the microstructure and mechanical properties for seven hot rolled microalloyed steels and deriving an empirical relation between the mechanical properties and the Nb/C ratio.
Combined Method of Electric Contact Heating and Diffusion Connection of Steel-Aluminum
Authors: Nozadze David , Macharadze Dimitri
Published: January 2012

A combined method of electric contact heating and diffusion connection of steel-aluminum is proposed which makes; an essential effect on three-phase shaping conditions, provides better physical contact and contact surface cleaning, formation and conservation of solid setting units. Activation of contact surfaces is achieved more effectively and quickly than at mechanical and vacuum treatment. Formation of physical contact and setting corresponds to contemporary conceptions of solid body model and kinetics of development of connection strength by the data of the carried out tests. Mechanical testing is carried out in static and dynamic modes, structure and phase composition in steel-aluminum joint is determined.
Effects of Pre-Aging on Bendability of an Asymmetric-Rolled Al-Mg-Si Alloy
Authors: Ogura Tomo , Hirose Akio , Sato Tatsuo
Published: January 2012

The effects of pre-aging before natural aging on the bendability of an asymmetric-rolled Al-Mg-Si alloy were investigated. In the specimen without pre-aging, hardness increased with natural aging time due to the formation of nanoscale cluster (nanocluster; Cluster (1)). The suppression of Cluster (1) during natural aging is clearly seen in the pre-aged specimens though the formation of Cluster (2). It was found that tensile properties were not so affected by the types of clusters. Bending test clearly showed that the pre-aging improves the bendability of this alloy. This effectiveness of pre-aging means Cluster (2) well contributes the deformability of this alloy compared with Cluster (1). Such an improvement of bendability is considered to be derived from the structure of nanoclusters and its interactions with the factor of plastically deformation of alloys.
Research on the Mechanical Properties of Al6061 Intermetallic Compounds Solubility as Manufactured by Spray Casting
Authors: Ryou Min , Baek Seung Yub , Kim Myung Ho
Published: January 2012

Al6061 alloys are well known as extrusion materials for automobile parts, aircraft. Recently, increasing demands of the lightweight for vehicles, materials have replaced steel are developed. Aluminum alloys are increasingly used as structural materials but in terms of mechanical properties, it is not a completed as a replacement for steel. The purpose of this study was to improve the mechanical properties and minimize the grain sizes of Al6061 matrix alloys for structural materials as produced by spray casting. Al6061 alloys were melted with 800°C in electrical resistance furnace. In order to form equilibrium concentration of Mg2Si (about 2 times) for Al6061, increased Mg and Si were added to Al6061 alloys and then preforms were prepared with molten metal by spray casting. The Specimens were fabricated by solution heat treatment and T6 age hardening. As a result of analyzing microstructure observations and mechanical properties according to supersaturated solid solution of Mg2Si for the final sample obtained, there were no changes in the size of the precipitates but precipitates per unit area were found to increase the area during the heat treatment processes. Mechanical properties such as tensile strength of over 80MPa and hardness of over 10HRB in spray casting have been increased according to solubility of Mg2Si.
Particle Stimulated Nucleation in Severely Deformed Aluminum Alloys
Authors: Sidor Jurij J. , Decroos Koen , Petrov Roumen H. , Kestens Leo A.I.
Published: January 2012

The microstructural changes were investigated in severely deformed 5182 alloy. The as-cast block was cold rolled with different reduction levels up to 98%. The deformation textures appearing after various rolling reductions account for minor qualitative changes (i.e. new texture components emerging with increasing rolling reductions) whereas significant quantitative differences were observed (i.e. changing intensity of rolling components). The presence of large non-deformable constituents affects both deformation and recrystallization textures. During rolling, large particles induce strain path changes in their vicinity, which produces microstructural heterogeneities. In recrystallization, the highly strained field around the particle induces particle stimulated nucleation (PSN). The current contribution tries to clarify the effect of different strain modes involved in severe plastic deformation on the development of recrystallization textures.
Superplastic Behaviour of AA5083 Aluminium Alloy with Scandium and Zirconium
Authors: Smolej A. , Skaza B. , Markoli B. , Klobcar Damjan , Dragojević V. , Slaček E.
Published: January 2012

The aim of the present investigation was to determine and to compare the superplastic behaviour of the AA5083 (Al-Mg-Mn) alloy with Sc and Zr additions. The investigated alloys were processed to form sheets by conventional hot and cold rolling. The superplastic properties were determined with strain rates in the range of 1x10-4 to 5x10-2s-1 and forming temperatures of 350 to 550°C. The results showed that the alloy with about 0.4% Sc exhibited a high superplastic ductility across a wide temperature range and strain rates up to 1x10-2s-1. The highest elongations to failure of about 2000% were attained at 550°C and at an initial strain rate of 5x10-3s-1. However, the alloy with about 0.15% Zr exhibited elongations up to 600%. The FSP processed Al-4.5Mg alloy with combined addition of about 0.2% Sc and 0.15% Zr exhibited good superplastic properties at higher strain rates (> 1x10-2s-1) with elongations up to 1500%.
Development of Grain Refinement in Aluminium Field
Authors: Sun Bao De , Han Yan Feng , Wang Jun
Published: January 2012

Some progresses of grain refinement in aluminium field in our group are involved in this paper. We invented a new preparation method of Al-Ti-B grain refiner with the application of high-intensity ultrasound in the preparation reaction. Owing to the optimization of TiB2 particles morphology in the prepared grain refiner, the commercial purity aluminium grains can be refined as small as 45μm, which is superior to the limiting level of the present commercial grain refiner, 120μm. First-principles calculations on the Al/TiB2 interface prove that the larger Al/TiB2 interfacial energy than that between α-Al and aluminium melt is responsible for the poor heterogeneous nucleation of α-Al on TiB2 particles with only TiB2 particles in melt. When there is redundant solute Ti in the melt, it is theoretically revealed that the spontaneous segregation of solute Ti on TiB2 particles plays an important role in the heterogeneous nucleation.
Effect of Cold Deformation on the Paint-Baking Response of Al-Mg-Si Alloy Sheet for Automotive Body
Authors: Tian Ni , Pan Lei , Liu Chun Cheng , Wang Jian Jun , Zhao Gang , Zuo Liang , Liu Chun Ming
Published: January 2012

The effect of cold deformation on the yield strength and precipitate behavior of Al-1.3Mg-1.2Si-0.5Cu-0.7Mn alloy sheet subjected to T4P temper for automotive body panels before and after paint-bake treatment were investigated by tensile test and differential scanning calorimetry (DSC) analysis. The results show that the T4P alloy sheet has significant work-hardening response (WHR), and the yield strength increment exceeds 190MPa as the tensile deformation strain approaches 15%. The unstrained T4P alloy sheet has obvious paint-baking response (PBR), and the yield strength increment is up to 80MPa, while the PBR of the cold stretched T4P alloy sheets decrease with increasing level of tensile deformation, and the minimal PBR is only 17.8MPa. The prior tensile deformation accelerates the precipitation of β″ and β′ phase from the T4P alloy matrix during paint-bake cycle but weakens the age-hardening response (AHR) and PBR of T4P alloy sheet. Moreover, it is evident that the T4P alloy sheet simulation paint-bake treated at 170°C for 30min can not fully exert the aging potential of the alloy sheet.
Manufacturing Slurry and Rheocasting of Hypereutectic Al-Si-Cu-Mg Alloy
Authors: Uetani Yasuhiro , Mori Nanako , Dohi Masayoshi , Matsuda Kenji , Ikeno Susumu
Published: January 2012

Both rapid and stable semi-solid slurry preparation of hypereutectic Al-14.8%Si-4.5%Cu-1.1%Mg alloy (in mass%) with fine solid granules as well as finely dispersed primary silicon particles was tried using a simple method newly developed, where the low-superheat melt passes through a gap between a rotating regular octagonal rotor and a circumscribed chill block. By examining effects of melt temperature running out from tundish, gap distance and rotational speed of rotor on solidification structure of the semi-solid slurry manufactured, the optimum making condition of the targeted semi-solid slurry was found out. Mean sizes of solid granules and primary silicon particles within the slurry, which had been made quickly with the good reproducibility, were 45μm and 20μm, respectively. Subsequently the obtained semi-solid slurries were rheocast into a cylindrical shape cavity by the use of a high pressure casting machine. It has been shown that the rheocast samples have peak hardness value between the gravity casting and the hot-extrusion, but a good age-hardenability somewhat higher than that of gravity casting.
Effects of Microstructures on Fatigue Behavior of an Al-Mg-Sc Alloy at an Elevated Temperature
Authors: Watanabe Chihiro , Monzen Ryoichi
Published: January 2012

Polycrystalline Al-1wt%Mg-0.27wt%Sc alloys bearing Al3Sc particles with different average sizes of 4 and 11nm in diameter have been cyclically deformed at 423K under various constant stress amplitudes, and the relationship between fatigue characteristics and microstructure of the alloy has been investigated. The specimen bearing 11 nm particles exhibited a cyclic hardening to saturation, while in specimens with the small particles a cyclic softening was observed after initial hardening. In the specimen with large particles, dislocations were uniformly distributed under all applied stress amplitudes, whereas the specimens bearing small particles, in which cyclic softening occurred exhibited clearly developed slip bands. The cyclic softening for the latter specimen was explained by particle shearing within the strongly strained slip bands. The width of precipitate free zones (PFZs) has been found to be one of the factors affecting the fatigue life of the specimens at 423K. The two-step aging decreases the width of PFZs, resulting in increase in the fatigue life.
Investigation of Quench Sensitivity of an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr Alloy
Authors: Xiong Bai Qing , Li Xi Wu , Zhang Yong An , Li Zhi Hui , Zhu Bao Hong , Wang Feng , Liu Hong Wei
Published: January 2012

In the present work, quench sensitivity of an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy is investigated by temperature-time-property (TTP) curve and TEM analysis, comparing with traditional AA 7B04 and AA 7150. The results indicate that the nose temperature of TTP curve and the corresponding incubation period of the alloy, AA 7150 and AA 7B04 are about 290°C/4.5s, 320°C/2.6s and 335°C/0.1s, respectively, The nose temperature of the alloy is the lowest among three alloys and the critical time at the nose temperature is the longest for the alloy, which is obvious that the alloy has lower quench sensitivity. Further TEM analysis shows that, with the prolongation of keeping time at the nose temperature, quench-induced precipitation phenomenon becomes obvious.
Deformability of Eutectic Al-Si Alloys Produced by Semi-Continuously DC Casting during Hot-Rolling
Authors: Hong Tao , Zhao Gang , Tian Ni , Yu Fu Xiao , Zuo Liang
Published: January 2012

The deformability and the microstructures of Al-12.2Si-0.6Mg alloy during hot-rolling were investigated by means of rolling the specimens of wedge bars with length of 180mm and width of 30mm, which had front thickness of 5mm and back thickness of 44mm.The wedge bars were cut from the ingots of the Al-12.2Si-0.6Mg alloy by the semi-continuously direct chill (DC in short) casting. The specimens of wedge bars were hot-rolled following holding between 410°Cand 480°C for different time. The results show that the size, morphology, distribution characters of eutectic Si particles in the Al-12.2Si-0.6Mg alloy can be remarkably modified by semi-continuously DC casting, which consists of coarse ribbon-like Si-particles with less than 5μm in length and 1μm in width and quite a lot eutectic phases of less than 0.4μm in size and space. The results also show that the ingots of the Al-12.2Si-0.6Mg alloy by the semi-continuously DC casting can possess excellent deformability during hot-rolling if the extent of heating is provided over 440°C for 60min and 410°C for 120min, and they cannot emerge cracked edges with the compression ratio of 85% by single-pass rolling. Their hot-plasticity depends on the size and space between eutectic phases in the ingots. Hot-rolling deformation makes ribbon-like Si phases in them crack and spheroidize, and then results in the sizes of coarse Si particles tending to be consistent.
Coatings of Ti and TiO2 with Defined Roughness for Implants by Gas Flow Sputtering
Authors: Lembke U. , Körtge A. , Neumann Hans Georg , Ortner K. , Jung T. , Lange Regina , Beck Ulrich
Published: January 2012

High rate film deposition via Gas Flow Sputtering was used to develop both metallic titanium films and ceramic titania coatings for implants. The structure formation of the coatings can be described by a modified model of structure zones according to Thornton. The potential of Gas Flow Sputtering for designing implant surfaces with controlled morphology and roughness is demonstrated.
The Effect of Mechanical Constraints on Gelatin Samples under Pulsatile Flux
Authors: Blangino Eugenia , Cagnoli Martín A. , Irastorza Ramiro M. , Vericat Fernando
Published: January 2012

It is of great interest in tissue engineering the role of collagen gel-based structures (scaffolds, grafts and-by cell seeded and maturation-tissue equivalents (TEs) for several purposes). It is expected the appropriate biological compatibility when the extracellular matrix (ECM) is collagen-based. Regarding the mechanical properties (MP), great efforts in tissue engineering are focused in tailoring TE properties by controlling ECM composition and organization. When cells are seeded, the collagen network is remodeled by cell-driven compaction and consolidation, produced mainly through the mechanical stimuli that can be directed selecting the geometry and the surfaces exposed to the cells. Collagen gels have different (chemical and mechanical) properties depending on their origin and preparation conditions. The MP of the collagen network are derived from the degree of cross-linking (CLD) which can be modified by different treatments. One of the techniques to evaluate MP in the network is by ultrasound (US). In this work we analyse the effect of several mechanical constraints (similar to that imposed to promote cell growth on certain sample surfaces, when seeded) on samples of gelatin with a specific geometry (thick walls cylinders) under loading conditions of pulsatile flow. We checked US parameters and estimates evolution of the network structure for different restrictions in the sample mobility. It was implemented by adapting devices specially built to measure elastic properties of biological tissues by US. The material (origin and purity) and the preparation conditions for the gelatin were selected in order to compare the results with those of literature.
Mechanical Properties of Thermomechanically-Processed Metastable Beta Ti-Nb-Zr Alloys for Biomedical Applications
Authors: Brailovski Vladimir , Prokoshkin Sergey , Inaekyan Karine , Dubinskiy Sergey , Gauthier Maxime
Published: January 2012

Metastable beta-titanium alloys combine exceptionally low Young's modulus and high biocompatibility, thus attracting special interest in the prospect of their application as biomedical implant material. In this work, Ti-21.8Nb-6Zr (at.%) ingots were manufactured by vacuum argon melting followed by hot isothermal pressing. The obtained ingots were thermomechanically processed using the following TMP sequence: a) cold rolling (CR) from e=0.37 to 2 of the logarithmic thickness reduction; and b) post-deformation annealing (PDA) of between 450 and 700°C (10’…5 h for 600°C and 1 h for other temperatures). The influence of the TMP on the alloy’s mechanical properties under static and cyclic loading was studied.
Development of a Collagen/Clay Nanocomposite Biomaterial
Authors: Reyna-Valencia Alejandra , Chevallier P. , Mantovani Diego
Published: January 2012

Collagen hydrogels are widely used as three-dimensional scaffolds for cells and tissue in culture environments. These materials, which consist of crosslinked biopolymer (protein-based) networks in aqueous media, are particularly suitable for recreating part of the extra-cellular matrix, but their poor mechanical properties represent a major limitation. One strategy to enhance the strength of this kind of hydrogels might be to incorporate clay nanoscopic particles. In fact, it has been observed that the charged surface of clay nanosheets can interact with certain functional groups belonging to polymer molecules, yielding stronger networks. Moreover, clay particles are recognized to be biocompatible. In the present work, the gelation process and the resulting morphological and mechanical properties of collagen/laponite clay nanocomposite hydrogels were invastigated. Upon gelation, the biopolymer molecules assemble into nanoscale fibrils, which bundle into fibers and entangle into a three-dimensional network. The network characteristics depend on tunable parameters such as pH and clay concentration.
Dynamic Recrystallization of Biomedical Co-Cr-W-Ni (L-605) Alloy
Authors: Favre Julien , Chiba Akihiko , Koizumi Yuichiro , Fabrègue Damien , Maire Éric
Published: January 2012

Compression tests are carried out at high-temperature on Thermec-master Z, followed by gas quench. Microstructures after deformation are evaluated using SEM-EBSD. Significant grain refinement occurs by dynamic recrystallization for high temperature and low strain rate (T>1100°C, SR<0.1s-1), and at high strain rate (SR~10s-1). Dynamic recrystallization is discontinuous and takes place from the grain boundaries, leading to a necklace structure. The nucleation mechanism is most likely to be bulging of grain boundaries. However, recrystallization occurs also by rotation of annealing twins. Thereafter the twin boundaries can bulge as well. The modeling of mechanical behavior gives a fair quantification of flow softening due to dynamic recrystallization indicating the progress of dynamic recrystallization with deformation.
Electrochemical Assessment of Cu-PIII Treated Titanium Samples for Antimicrobial Surfaces
Authors: Finke Birgit , Polak Martin , Hempel Frank , Schroeder Karsten , Lukowski Gerold , Müller Wolf Dieter , Weltmann Klaus Dieter
Published: January 2012

Titanium implant surfaces should ideally be designed to promote the attachment of target tissue cells. At the same time they should prevent bacterial adhesion, achievable through specific modification strategies. Copper could be well-suited as an antimicrobial finish, since it combines good antimicrobial properties with a certain bio-tolerance with regard to eukaryotic cells. In the present contribution, we evaluate electrochemical results of antimicrobial titanium surfaces generated by the insertion of copper. The surface was prepared via copper implantation into the titanium subsurface by means of plasma-immersion ion implantation (Cu-PIII) until a depth of about 30 nm. The amount and profile of copper ion implantation was changed by variation of the pulse length which was equivalent to the duty cycles of 0.2 % up to 90 %. Specimens containing 3 – 12 % copper (XPS) were used for electrochemical investigations with the help of the mini cell system in 0.9 % NaCl solution. The change in the shape of cyclic voltammograms demonstrated an alteration of the electrochemical behaviour. Copper oxidation peaks appeared in copper-implanted samples and their height was proportional to the copper concentration. These peaks are related to an electrochemical activity and not suppressed by the superficial titanium oxidation.
Evaluation of Bone Quality in Mandible of Young M-CSF Deficient-Induced Osteopetrotic Mouse
Authors: Fujitani Wataru , Lee Jee Wook , Nakano Takayoshi
Published: January 2012

The preferred crystallographic orientation of the biological apatite (BAp) c-axis has been shown to be one of the important bone quality indices that sensitively reflect in vivo stress distribution and dominate bone mechanical functions. The BAp orientation is expected to be regulated by bone modeling or remodeling by osteoblasts and osteoclasts whose primary functions are bone formation and absorption, respectively. Mouse with macrophage colony-stimulating factor (M-CSF) deficiency-induced osteopetrosis (op/op mouse) is a suitable animal model to elucidate the role of osteoclasts in the development of BAp orientation. In this study, the mandibles of 5-week-old mice were used because their mandible is subjected to complicated stresses including a biting stress locally applied just around the roots of the teeth and a bending stress applied along the mesiodistal axis of the mandibular body, and the response to the stress distribution is important to the formation of BAp orientation. The normal mouse mandible (control) has a one-dimension preferred BAp orientation in the mesiodistal direction, but just near the tooth root, the direction of BAp orientation changes locally to that of the tooth root responding to a biting stress. In the op/op mouse, the preferred BAp orientation only along the mesiodistal direction is found, but the degree is quite lower than that in normal mice. Moreover, the effect of biting was not observed in op/op mice because these mice are devoid of teeth eruption and are unable to bite. This suggests that M-CSF plays a critical role in forming the optimal BAp orientation, and therefore, the op/op mouse without osteoclasts cannot fully develop the appropriate bone microstructure in response to in vivo stress distribution, although BAp orientation is very sensitive to local in vivo stresses in normal animals with normal osteoclast function.
Effect of Energy Density of Incident Beam on Mechanical Property of Titanium Alloy Products Fabricated by Electron Beam Melting (EBM) Method
Authors: Fukuda Hidetsugu , Takahashi Hiroyuki , Kuramoto Koichi , Nakano Takayoshi
Published: January 2012

Electron beam melting (EBM) is a promising fabrication technique for directly producing metal products from powder as the starting material. Powders are provided as a thin layer (~100 μm) and melted layer by layer with an electron beam. In this study, the effects of the energy density of the incident beam on the mechanical properties of Ti–6 mass% Al–4 mass% V alloy products fabricated through EBM were examined. The products were fabricated using an electron beam at various energy densities depending on the electron beam current. The microstructures and crystallographic orientations were observed using optical microscopy and electron backscatter diffraction (EBSD), respectively. Compression tests were carried out in 2 loading directions using a mechanical testing machine equipped with strain gauges, one perpendicular (x–y direction) and the other parallel (z direction) to the stacking direction. In principle, the microstructure consisted of an acicular-shaped α phase (hcp lattice) and a small-volume β phase (bcc lattice). In addition, columnar grains elongated toward the z direction appeared during the repeated melting and solidification that occurred during the EBM process. An increase in the beam current of the incident beam enlarged the α grains and increased the relative density, resulting in the related Young’s modulus of the products. The energy density caused by the beam current also introduces anisotropy in the deformation behavior depending on the loading axis toward the stacking direction. This is closely related to the cast defect arranged along the stacking layers. It was concluded that the mechanical properties of the Ti–6 mass% Al–4 mass% V alloy products formed through EBM were very sensitive to the incident beam current and stacking direction, resulting in the exhibition of anisotropic deformation behavior within a limited range of energy density.
How Oxygen Influences the Deformation Mechanism of the “Gum Metal” Titanium Alloy Composition
Authors: Gloriant T. , Besse M. , Castany Philippe , Cornen M. , Gordin D.M. , Laillé D.
Published: January 2012

In this work, Ti-23Nb-0.7Ta-2Zr (TNTZ) and “Gum Metal” Ti-23Nb-0.7Ta-2Zr-1.2O (TNTZ-O) alloys were synthesized by cold crucible levitation melting (CCLM) with the objective to investigate the influence of oxygen on the deformation mechanisms. By tensile tests and EBSD analyses, we showed that the deformation in the TNTZ-O alloy is only accommodated by dislocation slip. Thus, the addition of oxygen leads to suppress the formation of α” martensite and prevents the twinning deformation mechanism.
Preparation of HA-Coated Mg-4.0Zn-1.0Ca-0.6Zr(wt%) Alloy and its Biodegradation Behaviors
Authors: Huang Hong Qian , Guan Ren Guo , Zhao Tong , Zhao Zhan Yong , Cao Fu Rong
Published: January 2012

Magnesium and magnesium alloys, as biomaterials, possess many properties that are superior to those of other metals. However, magnesium and magnesium alloys have strong chemical activity and porous and brittle surface oxide film, as degradable implantation materials, their degradation rates are too fast. Hydroxyapatite (HA) has good biocompatibility and biological activity and has become one of the replacement materials of biomedical stiff hemopoietic tissue, but the application of HA biomaterial is hindered because HA is brittle and has low strength. Integrating good mechanical properties of metallic materials with excellent biological performance of HA, the composite obtained by coating HA to the surface of metallic matrix is ideal rehabilitation material of bone tissue. In the present study, a new Mg-4.0Zn-1.0Ca-0.6Zr (wt%) was designed according to the requirements of biocompatibility. The microstructures and the mechanical properties of the new alloy were investigated by experiment. The excellent mechanical properties fully meet the service requirements of human bone tissue for mechanical property. Flat and dense hydroxyapatite coating was prepared on the surface of magnesium alloy matrix by preceding alkali heat treatment, electrodeposition and post alkali heat treatment. The Structure and constituent of HA coating and the biodegradation behavior of HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy were evaluated. Resuls showed that the degradation rate of HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy in SBF biomimetic solution decreased obviously and tended to be stable after 10 days. As degradable implantation materials, HA-coated Mg-4.0Zn-1.0Ca-0.6Zr (wt%) alloy fully meets the service requirements of human bone tissue.
In Vitro Degradation of Ultrafine Grained Mg-Zn-Ca Alloy by High-Pressure Torsion in Simulated Body Fluid
Authors: Guan Shaokang , Ren Zhen Wei , Gao Jun Heng , Sun Yu Feng , Zhu Shi Jie , Wang Li Guo
Published: January 2012

In this paper the in vitro degradation of ultrafine grained (UFG) Mg-Zn-Ca alloy produced by HPT was investigated by electrochemical measurements and immersion tests in SBF. It was found that UFG Mg alloy had better degradation properties and also higher microhardness value than as-cast Mg alloy. The corrosion current density of UFG Mg alloy decreased by about two orders of magnitude, compared with that of as-cast alloy. Through electrochemical impedance spectroscopy (EIS) test，UFG Mg alloy showed a higher charge transfer resistance value. In immersion test, UFG Mg alloy in SBF exhibited more uniform corrosion and lower degradation rate (0.0763 mm/yr) than as-cast alloy. The degradation properties were related with the microstructure evolution, namely the grain refinement and redistribution of second phase. Keywords: Mg-Zn-Ca alloy; High-pressure torsion (HPT); Degradation behavior; Simulated body fluid (SBF); Microhardness
Regeneration of Bone Mass and Bone Quality around Implant with Grooves for Aligning Bone Cells in Rabbit Hindlimb Bones
Authors: Ishimoto Takuya , Kawata Kentaro , Sakai Takashi , Yoshikawa Hideki , Nakano Takayoshi
Published: January 2012

It was reported that one-dimensionally elongated pores in implants promote the production of new bone tissue possessing both high bone density and the preferential alignment of biological apatite (BAp) c-axis/collagen as a bone quality parameter. This finding indicates that the anisotropic orientation and/or migration of osteoblasts guided by the grooved-pore surface affected the establishment of the anisotropic microstructure of bone tissue. In this study, a grooved polytetrafluoroethylene (Teflon) implant, which may have a role in regulating osteoblast arrangement, was prepared to investigate the relationship between cell behavior and bone microstructure. A cylindrical Teflon implant with 8 grooves on its side was prepared. The width and depth of the groove cross-section were 0.5 and 0.75 mm, respectively. Each implant was inserted in a drill-hole defect created on a rabbit femur such that the groove direction was parallel or perpendicular to the long bone axis in which the BAp c-axis aligns one-dimensionally. The Young’s modulus of Teflon is approximately 0.5 GPa, much lower than that of bone; therefore, the effects of applied stress can be eliminated in this model. The oriented new bone was preferentially produced along the grooved surface. The alignment direction of the BAp c-axis was almost parallel to the grooved surface even near the surface vertically aligned to the long bone axis. The geometry of the implant surface can control the organization of BAp alignment through the arrangement of osteoblasts to orient and subsequently to migrate along the surface direction; hence, implant geometry, particularly the groove, is considered an important factor controlling the BAp orientation of regenerated bone tissues.
Influence of Shape Memory Properties on Sliding Resistance in Fixed Orthodontic Appliances
Authors: Jordan Laurence , Garrec Pascal , Prima Frédéric
Published: January 2012

Tooth movements in an orthodontic treatment are the result of an applied force system, wire-bracket-ligature, and the response of the bone tissue. Starting an orthodontic treatment, it is necessary to exercise a sufficient initial force and then to maintain to obtain a continuous tooth movement. Orthodontic wires, which generate the biomechanical forces, usually transfer forces through brackets to trigger tooth movement. In the case of excessive forces of friction, they are behaving as an opposing force with respect to the movement of the tooth, making it sometimes slower or incontrollable [1].
Influence of Hydrogen Discharged from Palladium Base Hydrogen Storage Alloys on Cancer Cells
Authors: Kagawa Akio , Katsura Keishi , Mizumoto Masayuki , Tagawa Yutaka , Masiko Yoichi
Published: January 2012

The influence of discharged hydrogen from Pd-Ni based hydrogen storage alloys (HSAs) on cultured cells has been investigated. The susceptibility of cells to discharged hydrogen varied with the kind of cells. No influence was seen in the normal cells, while an effect of killing cancer cells was observed near the HAS and the region where the cell death was observed was limited to an extent of a few mm from the alloy surface. In order to examine the cause of the effects, the amount of gaseous hydrogen and hydrogen radicals released from the alloy surface and pH change of physiological saline aq. solution were measured. The amount of gaseous hydrogen and hydrogen radicals increased with time. The pH of physiological saline aq. solution decreased first and then recovered to the starting value after about 50h. The pH change behavior varied with alloy composition. It is inferred that the hydrogen radicals formed on alloy surface may bring a characteristic change in the cancer cells, leading to the effect of discharged hydrogen on cancer cell death.
Effect of Heat Treatments of Bioactive Nacre on HAp Formation in SBF
Authors: Kobayashi Sengo , Ui Michiko , Araikawa Hayato , Sakamoto Tatsuaki , Nakai Kiyomichi
Published: January 2012

Formation of hydroxyapatite (HAp) in simulated body fluid (SBF) on heated nacre has been examined. Nacre is known as composite layer of aragonite platelets and organic materials. Nacre was obtained from the shell of Akoya pearl oyster after removing its prismatic layer. The nacre was heated up to 300°C in air and then soaked in SBF. Nacre heated at 300°C lost iridescent color and became brittle, implying that organic materials which plays a role as glue between aragonite platelets mostly disappeared by heating at 300°C. Formation of HAp particles on nacre in SBF was easier than that on pure Ti. Maximum formation rate of HAp particles was obtained on the nacre heated at 200°C. The amount of HAp particles formed on the nacre heated at 300°C is the smallest. The organic materials in nacre play a critical role for HAp formation on nacre in SBF.
Electron Beam Melting: Moving from Macro- to Micro- and Nanoscale
Authors: Koptioug Andrey , Rännar Lars Erik , Bäckström Mikael , Klingvall Rebecca P.
Published: January 2012

This paper presents some results achieved in the biomedical applications of the EBM® technology, and describes the resolved and unresolved challenges presented by modern medical implant manufacturing. In particular it outlines the issues related to the cellular structure design and metal surface modification. Moving to precision control of the metal surface at a micro-and sub-micrometer scale is a serious challenge to the EBM® processing, because it uses the powder with average grain size of about 0.04 to 0.1 mm. Though manufacturing of components with solid-mesh geometry and porous surfaces using EBM® is quite possible, post-processing (for example chemical or electrochemical) is needed to achieve desired control of the surface at smaller scales to realize full potential of the technology for biomedical applications.
Osteoconductive TiO2 Coating on Titanium Using Anodizing in High Content Phosphoric Acid
Authors: Kuroda Kensuke , Ichino Ryoichi , Okido Masazumi
Published: January 2012

In this study, anodizing of Ti in the various concentration of H3PO4 aqueous solutions gave TiO2 films, and the osteoconductivity was examined using in vivo testing. In the anodizing treatment, anodizing potential of < 200 V was applied to the Ti substrate in H3PO4 aqueous solutions with the concentration of 0.1 to 14 M at 298 K. The coatings were evaluated using SEM, XRD, FT-IR and XPS. In in vivo testing, the coated samples were implanted in the rats’ tibia for 14 d to evaluate the osteoconductivity. In H3PO4 aqueous solutions with any concentration, anatase-type TiO2 films were obtained on the Ti substrate by anodizing. The crystallinity of anodized TiO2 films depended on the concentration of H3PO4 and sparking. In less than 2 M H3PO4, anatase with high crystallinity was formed. On the other hand, anodizing with sparking in more than 4 M H3PO4, gave low crystallinity anatase film. In in vivo testing, osteoconductivity of the coatings with low crystallinity anatase was much higher than that with high crystallinity.
Quantitative Analysis of the Cellular Actin Cytoskeleton on Geometrically Designed Surface Topography
Authors: Matschegewski Claudia , Birkholz Harald , Staehlke Susanne , Loeffler Ronny , Kern Dieter P. , Engel Konrad , Nebe Barbara
Published: January 2012

In tissue engineering, topographical modification of implants has been used as a powerful tool for the development of biorelevant implant designs. However, there is still a lack of knowledge about the fundamental principles of the cell–material interaction and quantitative correlations between cell biological parameters and physicochemical surface characteristics. The focus of our studies on cell architecture–cell function dependencies on regular micro-scaled surface structures was to investigate and further quantify the cell phenotype obtained from images of confocal microscopy and scanning electron microscopy. We used periodically structured titanium surfaces with regular cubic pillar geometry (dimension 3x3x5 µm and 5x5x5 µm) in comparison to planar samples. Confocal microscopy revealed a considerable rearrangement of the actin cytoskeleton on the top of the pillars with a reduced filament length. The quantification of different actin filament networks of cells grown on structured surfaces was carried out with a novel software for automatic filament recognition, covering the majority of filaments and their branching in noisy data. The quantitative analysis of cell phenotype changes on surfaces with regular geometry opens new possibilities for the data correlation cell vs. material.
Mechanical Properties of Ti-Cr-Sn-Zr Alloys with Low Young’s Modulus
Authors: Murayama Yonosuke , Sakashita Hiromasa , Kimura Hisamichi , Chiba Akihiko
Published: January 2012

This work investigates the mechanical properties of Ti-Cr-Sn-Zr alloys containing large amount of Zr. We focuses on the effect of the varying alloy composition on the microstructure, the Young’s modulus, the deformation mechanism and the deformation behavior. Ti-Cr-Sn-Zr alloys show much low Young’s modulus in the narrow composition range for Cr but wide for Zr. The Young’s modulus of Ti-2Cr-6Sn-xZr (x=5~60mass%) alloy decreases with increasing Zr and shows the minimum value of 41GPa in Ti-2Cr-6Sn-45Zr alloy. The alloys with low Young’s modulus consist in meta-stable β phase. The composition of the meta-stable β phase is close to the transition where the quenched microstructure transits from martensite to meta-stable β phase. Ti-2Cr-6Sn-45Zr alloy with lowest Young’s modulus show the super-elastic property.
Young’s Modulus Changeable Titanium Alloys for Orthopaedic Applications
Authors: Nakai Masaaki , Niinomi Mitsuo , Zhao Xiao Li , Zhao Xing Feng
Published: January 2012

A novel biomedical titanium alloy with the ability to undergo self-adjustment in its Young’s modulus was developed. In spinal fixation devices, the Young’s modulus of the metallic implant rod should be sufficiently high to suppress springback for the surgeon, but should also be sufficiently low to prevent stress shielding for the patient. Therefore, deformation-induced ω phase transformation was introduced into β-type titanium alloys so that the Young’s modulus of only the deformed part would increase during operation, while that of the non-deformed part would remain low. The increase in the Young’s modulus due to cold rolling was investigated for a binary Ti-12Cr alloy (mass%). Microstructural observation and Young’s modulus measurement reveal that the Ti-12Cr alloy undergoes deformation-induced ω phase transformation and exhibits the increase in the Young’s modulus by deformation.
Osteoblast Behavior In Vitro in Porous Calcium Phosphate Composite Scaffolds, Surface Activated with a Cell Adhesive Plasma Polymer Layer
Authors: Nebe Barbara , Cornelsen Matthias , Quade Antje , Weissmann Volker , Kunz Friederike , Ofe Stefan , Schroeder Karsten , Finke Birgit , Seitz Hermann , Bergemann Claudia
Published: January 2012

Synthetic materials such as bone substitutes are permanently under development for applications in orthopedic and trauma surgery. Our porous scaffolds were produced from ß-tricalcium phosphate (TCP) using the three dimensional (3D)-printing technology. After sintering the porosity and the pore size of the 3D printed scaffolds reached nearly 50 % and 500 µm, respectively. TCP scaffolds were additionally stabilized by infiltration with polylactic acid (PLA). Because PLA usually impeded cell adhesion we activated the composite surface with plasma polymerized allylamine in a low temperature plasma process. For cell investigations inside the scaffold we used a module system, where two porous discs can be horizontally fixed within a clamping ring. Thereby a 3D cell culture module with four levels and a maximal height of 10 mm was generated. Human MG-63 osteoblasts (ATCC) were seeded apically and placed in serum-containing DMEM. After 14 days of a static cell culture the cell ingrowth and mobility was analyzed by scanning electron microscopy. Osteoblast's initial adhesion and short time occupation of the surface is significantly improved on plasma polymer activated TCP surfaces, which could be a precondition for an enhanced colonization inside a calcium phosphate scaffold. Interestingly, the plasma functionalization of the pure TCP scaffold was possible and successful concerning cell acceptance.
High Performance Beta Titanium Alloys as a New Material Perspective for Cardiovascular Applications
Authors: Prima Frédéric , Sun F. , Vermaut Philippe , Gloriant T. , Mantovani Diego , Jacques Pascal J.
Published: January 2012

During the last few decades, titanium alloys are more and more popular and developed as biomedical devices because of their excellent biocompatibility, very good combination of mechanical properties and prominent corrosion resistance [1-3]. Recently, a new generation of beta titanium alloys dedicated to biomedical applications has been developed. Based on biocompatible alloying elements such as Ta, Nb, Zr and Mo, these alloys were designed as low modulus alloys [4] or nickel-free superelastic materials [5, 6] mainly for orthopedic or dental applications as osseointegrated implants. Beta type titanium alloys take great advantages from their capacity to display several deformation mechanisms as a function of beta phase stability. Therefore, from low to high beta stability, stress assisted martensitic phase transformation (β-α’’), mechanical twinning or simple dislocation slip can alternatively be observed [7]. As a consequence, a very large range of mechanical properties can be reached, including low apparent modulus, large reversible elastic deformation or high yield stress. Although titanium alloys display now a long history of successful applications in orthopedic and dental devices, none of them have been commercially exploited in the area of coronary stents, despite their superior long term haemocopatibility compared to the 316L stainless steel. However, according to previous researches on the biocompatibility of various metals, the corrosion behavior of stainless steel is dominated by its nickel and chromium components, which may induce redox reaction, hydrolysis and complex metal ion–organic molecule binding reactions, whereas none are observed with titanium [8, 9].
Reconstituted Extracellular Matrix Improve Osteoblastic Differentiation onto Titanium Surfaces
Authors: Rimondini Lia , Demarosi Federica , Foltran Ismaela , Quirici Nadia
Published: January 2012

Electrospinning technique is an efficient processing method to manufacture micro-and nanosized fibrous structures by electrostatic force for different applications. In biomaterial field, electrospinning technique has been successfully utilized to prepare new drug delivery materials and tissue engineering scaffolds. Fiber mats of biodegradable polymers having a diameter in the nanoto submicro-scale can be considered to mimic the nanofibrous structure of native extracellular matrix (ECM). Native extracellular matrix, constituted of proteins and polysaccharides improving cells growth in its nanofibrous porous structure, controls not only the cell phenotype, but the whole structure of the biological tissues. In the present study we investigated the effect of electrospun reconstituted collagen fibers onto metals for oral implants devices manufacturing as far as the osteoblastic differentiation potential of stem cells and cytofunctionality of osteoblasts in-vitro. The cells cultured onto titanium samples coated with ECM constituents showed faster osteoblastic differentiation and more efficient deposition of mineralized matrix in comparison with those onto uncoated substrates.
The Analysis of Hip Joint Prosthesis Head Microstructure Changes during Variable Stress State as a Result of Human Motor Activity
Authors: Szarek A. , Stradomski Grzegorz , Włodarski J.
Published: January 2012

The paper present the analysis of metal prosthesis head stress state of hip joint endoprosthesis which is a result of variable loads during human motor activity and its influence on the erosion of materials. The analysis of stress state was made with use of FEM – ADINA numerical tool. The analysis of surface erosion process was made with use of the scanning electron microscope. To the researches was taken for heads from CoCrMo bearing shell and polyethylene UHMWPE.
Corrosion Behavior and Surface Analysis of Melt-Spun Mg-Based Metallic Glass in Physiological Saline Solution
Authors: Wang Yong Sheng , Tan Ming Jen , Jarfors Anders W.E.
Published: January 2012

The developed Mg-based metallic glass shows great potential as implants in biomedical applications instead of crystalline Mg alloys, which may possesses acceptable corrosion properties. In this study, corrosion behaviors of melt-spun amorphous Mg67Zn28Ca5 ribbons were investigated in physiological saline solution. Electrochemical testing and hydrogen evolution rate indicated that the glassy ribbons obtained at lower wheel speed were more noble with smaller corrosion current, and possessed a comparatively lower corrosion rate in physiological saline solution. Surface morphology analysis revealed that glassy Mg67Zn28Ca5 ribbons exhibited a strong susceptibility to localized pitting corrosion. A Zn-rich passive layer was formed on the surfaces of the glassy ribbons, indicating that Zn was an effective alloying element to enhance the corrosion resistance of amorphous Mg67Zn28Ca5 alloys.
Orientation Relationships between Directionally Grown Precipitates and their Parent Phases in Steels
Authors: Lee Dong Nyung , Han Heung Nam
Published: January 2012

There are four prominent orientation relationships (ORs) between directionally grown precipitates and their parent phases in steel. They are ORs between ferrite precipitate and parent austenite (the Kurdjumov and Sachs OR), between orthorhombic cementite precipitate and parent austenite (the Pitsch OR), between cementite precipitate and parent ferrite (the Bagaryatski OR) and between hexagonal molybdenum carbide precipitate and parent ferrite (the Dyson et al. OR). The directed precipitation occurs at low transformation temperatures. The ORs have been explained by the directed growth model. The solid phase transformation of a metastable phase into a stable phase needs the activation energy. The energy is usually supplied in the form of thermal energy. When the nucleation takes place, the strain energy may develop in the stable nucleus and the metastable matrix. The strain energy can result from a difference in density between the nucleus and matrix and the lattice mismatch along the nucleus:matrix interface. The fundamental concept of the model is that the maximum growth rate of precipitate is along the direction that generates the maximum strain energy and the interface energy is minimized. The four ORs are determined, based on the concept, such that the mismatch along the interface between the minimum shear modulus planes of precipitate and its parent phase that are parallel to the maximum Young’s modulus direction of the precipitate is minimized.