Search

This study is aimed to evaluate the influence of mechanical surface treatment on the degradation response, cell survival, adhesion, and proliferation of a TiMg composite material. Two sets of the TiMg samples with different surface characteristics were studied: i) as-machined samples (TiMg-T) and ii) samples with a mechanically modified surface (TiMg-P). Surface roughness was determined using a confocal microscope. Degradation rates (DR) were evaluated in artificial Plasma, HBSS, and NaCl 0.9%. The cell viability was evaluated using an MTT assay. The initial cell adhesion and spreading were investigated using the direct contact assay. An xCELLigence system was employed to provide real-time cell proliferation. The focal adhesion and cell morphological changes were also examined. The DR of TiMg-P decreased by ⁓5 times compared with that of TiMg-T. Surface of the TiMg-P specimens after 72 h exposure to either HBSS or Plasma was passivated by a layer enriched with bioactive Ca/P species. The cell viability of L929 and Saos-2 after 72 h incubation for TiMg-P was 94.6% and 94.8% compared with 73.8% and 74.3% obtained for TiMg-T, respectively. The direct contact assay showed that the initial adhesion and spreading of the L929 cells incubated with TiMg-P was more pronounced compared with that of TiMg-T. The proliferation rate of Saos-2 cells incubated with TiMg-P was higher when compared with that of TiMg-T, and was almost comparable to that of the DMEM-blank between the 24 and 72 h interval. TiMg-P had a pronounced difference in the number and area of Focal Adhesions (FA) compared with that of TiMg-T. The morphology of cells incubated with TiMg-P was not altered. The results confirmed that the smooth and less strained surface of the TiMg-P samples effectively improved the in-vitro degradation response, cell survival, adhesion, and proliferation.

The deformation and strengthening behavior of an ultra-fine grained (UFG) Al fabricated via powder metallurgy was investigated over a wide range of homologous temperatures (TH). Our results reveal that the presence of a high density of γ-Al2O3 nanoparticles, located primarily at high angle grain boundaries (HAGBs), promoted remarkable stabilization of the Al grain structure up to TH = 0.94. The 0.2% strain offset yield stress (YS0.2) of the materials annealed at 600 °C for 24 h with grain sizes (d3D) of 0.57, 1.67, 2.33 and 2.99 μm was systematically studied from room temperature (RT) to 600 °C. Our study reveals that with decreasing d3D the strain hardening ability of the materials gradually decreased, and this behavior became pronounced at elevated T, which was attributed to the onset of plastic instability. The YS0.2 of the materials at all T followed the relation YS0.2 = a + k d3D−0.5. As determined on the basis of data interpolation, a positive transition from an established Hall-Petch (HP) relation at RT occurred at d3D = ∼8 μm. As the parameter a was negative at RT and 300 °C the documented strength–structure relationship cannot be explained on the basis of a Hall-Petch relation. The γ-Al2O3 particles located at HAGBs did not contribute notably to RT strengthening, whereas GBs played a significant role in the overall strength. The materials showed a high YS0.2 up to a TH of 0.94. The YS0.2 was observed to be linearly correlated with the reciprocal square root of the d3D and the coefficient k followed k = 224.4–0.376 T relation. The HP model overestimated the YS0.2 values at elevated T namely for the materials with a smaller d3D. It is proposed that softening occurred as a result of the γ-Al2O3 particles densely distributed within a 3D network, which were included in Hansen's strengthening model; particle strengthening played a role at elevated T.

An aluminum material stabilized with a 1.6 vol% of nanometric Al2O3 dispersoids, named HITEMAL, was fabricated by hot extrusion of a fine atomized Al powder. The Al2O3 dispersoids stemmed from a native Al2O3 films on an aluminum powder surface. An extruded rod of the material was then cold-deformed out into a thin wire by rotatory swaging, hydro extrusion and rolling. Such severely deformed HITEMAL was studied as a prospective outer sheath stabilizer material for MgB2 core superconductor wires. An emphasis was put on the effect of annealing realized at various temperatures close to the melting point of Al, which is typically applied to form an in-situ MgB2 superconductive core, on the mechanical and electrical properties of the HITEMAL wire. A systematic investigation was performed of changes to a severely deformed Al grain structure and Al2O3 dispersoids upon annealing the as-deformed wire from 595 to 655 °C for 30 min. Mechanical and electrical properties of the wire were measured at room and cryogenic temperatures. The results showed that the ultrafine-grained Al + 1.6 vol% Al2O3 wire exhibited advantageous properties, and surface integrity after annealing up to 642 °C. It is thus a lightweight material of choice for outer sheaths of MgB2 superconductors. Keywords: Aluminum (Al), Lightweight, Magnesium diboride (MgB2), Mechanical properties, Microstructure, Superconductor

The mechanical properties of thermally stable ultrafine-grained Al metal matrix composites dispersion strengthened and stabilized by nano-metric in-situ Al2O3 (named HITEMAL©) fabricated by powder metallurgy (PM) were tested by small punch testing (SPT) in a broad temperature range from a room temperature (RT) to 500 °C. By changes to PM approach and applied processing parameters four specific HITEMAL© materials with different Al grain structure, and different morphology and distribution of Al2O3 dispersoids were fabricated and characterized by transmission electron microscopy and energy-dispersive X-ray spectroscopy. The effect of microstructural features on the mechanical properties of HITEMAL© materials was pursued by SPT. The SPT results were compared and correlated with the results obtained by conventional tensile testing. It was confirmed that a mutual correlation of tensile test and SPT results strongly depended on the particular testing temperature. As a result of microstructural differences between HITEMAL© materials the correlation between tensile test and SPT results changed quite significantly for each studied material. The analysis of fractured SPT discs by scanning electron microscopy (SEM) revealed the transformation in fracture mechanism during SPT from ductile to brittle behavior as the testing temperature increased from RT to elevated temperatures. If the testing temperature was considered as a parameter, the precision of yield strength calculation from SPT results improved significantly in whole temperature range. Data Availability The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

This study introduces in-situ aluminum (Al)-aluminum nitride (AlN) metal matrix composites (MMCs) manufactured by a powder metallurgy (PM) cost-effective approach realized at a large industrial scale. The Al-AlN MMCs were targeted for structural load-bearing applications with an expected service at elevated temperatures not normally associated with a use of conventional Al-based alloys and MMCs. Commercial Al, magnesium, and tin powders were processed by readily available PM techniques of blending, cold isostatic pressing (CIP), a solid-state nitridation in a static gaseous nitrogen, and a hot direct extrusion. Two sound voids free Al + 8.8 and 14.7 vol% AlN MMCs were reproducibly fabricated in a form of the long extruded bars with the cross-section of 80 × 15 mm. The microstructure of nitrided and extruded MMCs was presented in details. A typical yolk-shell-like microstructure of Al metallic core and nitrided layer was formed homogenously in a volume of the CIP bulky (~25 kg) billets upon nitridation. The microstructure of extruded Al-AlN MMCs consisted of Al grains elongated into the extrusion direction. The Al grain structure was embedded with the evenly distributed micrometric regions formed by a high density AlN nanocrystals in Al matrix. A stability of the tensile mechanical properties of as-extruded Al-AlN MMCs was pursued in transversal and longitudinal directions after the annealings performed at 300–600 °C for 24 h. Owing to an effective stabilization by the stable and fine AlN dispersoids by Zener pinning action no major changes to the mechanical properties took place after annealing up to 500 °C.

The length-scale effects on the load bearing capacity of reinforcement particles in an ultrafine-grained metal matrix composite (MMC) were studied, paying particular attention to the nanoscale effects. We observed that the nanoparticles provide the MMCs with a higher strength but a lower stiffness compared to equivalent materials reinforced with submicron particles. The reduction in stiffness is attributed to ineffective load transfer of the local stresses to the small and equiaxed nanoparticles.

This work presents a titanium (Ti) - magnesium (Mg) composite as a novel material that is designed for application in biomedical devices that are subjected to intense and cyclic loading (such as dental implants). This study concentrates on how the mechanical properties, fatigue endurance, in-vitro corrosion response and cytotoxicity of TiMg composites depend on the use of high-purity regular-morphology plasma atomized (PA) Ti Grade 1 powders. It also compares the desired results with those obtained for composites fabricated using hydride–dehydride (HDH) Ti Grade 4 powders. The results showed that the as-processed Ti(PA)+17 vol% Mg composite exhibited an attractive combination of an ultimate tensile strength (UTS) of 450 ± 1 MPa, 0.2% strain offset yield stress (YS0.2) of 331 ± 5 MPa, and elongation (e) of 8.9 ± 1%), in addition to a reduced Young’s elastic modulus (E) of 88 ± 0.1 GPa. Moreover, the as-processed Ti(PA)+17 vol% Mg composite showed a reasonable fatigue life, while it reached a fatigue tensile stress of 260 MPa at 1.5·107 cycles. The advantageous mechanical properties of the Ti(PA)+17 vol% Mg composite, superior to those of Ti(HDH)+Mg counterparts, resulted from a specific ultrafine Ti grain structure. The corrosion behavior of the Ti(PA)+17 vol% Mg composite was systematically studied during immersion in a Hank’s balanced salt solution (HBSS) for up to 21 days. The elution of Mg enabled a further decrease of E down to 84.3 ± 0.3 GPa, while the tensile strengths remained unaffected, and e and fatigue stress decreased. Nevertheless, the mechanical performance of eluted Ti(PA)+17 vol% Mg remained appropriate for a specific application of dental implants with the addition of porosity induced osseointegration. Owing to a refined Mg grain structure, in-vitro corrosion tests confirmed a reduced elution rate of the Mg component from Ti(PA)+17 vol% Mg when compared with that of Ti(HDH)+Mg counterparts. The cytotoxicity assays demonstrated that as-extruded Ti(PA)+17 vol% Mg exhibited a nontoxic response upon culturing with resistant hAD-MSC cells, which was comparable with that of the commercial purity (CP) Ti Grade 4 reference material. For a highly sensitive L929 cell line, the metabolic activity of Ti(PA)+17 vol% Mg had to be increased by surface pretreatment of a TiMg sample. All results of this study indicate that the new Ti(PA)+17 vol% Mg composite is immensely promising for use in prosthodontic surgery.

Powder metallurgy (PM) commercial purity titanium (CP Ti) was fabricated and studied, with an aim of utilization for dental application. PM CP Ti was manufactured using a cost effective approach, where affordable hydrogenation–dehydrogenation (HDH) process Ti 99.4 wt.% powder was consolidated via the following sequence of PM techniques: cold isostatic pressing, warm vacuum pressing at 420 °C and warm direct extrusion at 500 °C. The paper presents the first studies on processing, microstructure, testing of mechanical properties, fatigue performance and bonding strength with different veneer coatings. By employed consolidation process sound material with low porosity (1.5%) and sustained oxygen content (0.21 wt.%) was attained. The tensile properties obtained for PM CP Ti (UTS = 701 MPa, YS0.2 = 512 MPa, ε = 13 %) were improved over to those for cast / milled CP Ti Grade 4 reference, the material commonly used in dentistry. Tested using the ISO 14801 standard for dental implants, the samples machined from PM CP Ti showed fatigue performance similar to CP Ti Grade 4. PM CP Ti used as a metal base material in restoration metal – ceramic systems showed very good bond strength with three commercially available veneering ceramics and complied with the ISO 9693 standard. Within the limitations of this paper, the preliminary results demonstrated that performance of economic PM CP Ti is equal or superior to CP Ti Grade 4 reference material and it can be used in prosthodontics.

The aim of this study was to evaluate the In-vitro response, including cytotoxicity, genotoxicity, and oxidative stress, of a pretreated dental implant (DI) that was produced from a novel partially biodegradable Ti17Mg composite material. Viability and adhesion, and morphological alteration of Mouse fibroblast NCTC clone 929 cell line (L929) and human Dental Pulp Stem Cells (hDPSCs) were evaluated using MTT and live/dead assays. The genotoxic potential was investigated by comet and plasmid DNA interaction assays. The oxygen reactive species (ROS) formation was detected by Oxidative stress testing. The results showed surface pretreatment by 20 h prewashing in Hank's balanced salt solution (HBSS) at 20 mL.cm−2 concertation minimized the hypermagnesemia effect. Compared with the Ti Grade 4 (TiGR4) reference EDS analysis confirmed formation of a Ca/P-rich biomimetic layer on the surface of Ti17Mg DI after extraction in DMEM. The indirect MTT assay revealed that Ti17Mg DI extracts exerted a mild level of cytotoxicity without any induced morphological alteration of the incubated cells. The direct assays showed that the initial cell adhesion and proliferation were improved. No DNA damage was induced by Ti17Mg DI. No detection for smearing or loss of plasmid DNA was found. Oxidative stress confirmed no increase in ROS levels. In-vitro evaluation study confirmed a desirable In-vitro response of pretreated Ti17Mg that was comparable to that of the TiGR4 reference. The obtained results suggest the Ti17Mg composite exhibits a promising application potential as a material for the fabrication of DI.

Background: One of the main issues concerning dental implant materials arises from their Young’s modulus being considerably higher than that of bone, which can generate stress-shielding effect and periimplant bone atrophy during loading. By use of advanced powder metallurgy novel titanium-magnesium (Ti12Mg) composite has been designed and consolidated. Results of ISO-standard based tests for dental implants demonstrated superior mechanical properties, in-vitro tests showed adequate biocorrosion. Aim: The aim of the study was to produce common dimension implants and assess the in-vivo osseointegration potentials of Ti12Mg composite metal on animal model. Materials and methods: Study design was presented to ethical committees of both UNIZG School of Dental Medicine and UNISA Faculty of Veterinary Medicine, and the approvals acquired. Consolidated Ti12Mg implant material was roll-pressed into a 3, 5mm diameter bar and machined into 12 implants of 11mm length. Implant neck geometry was modeled to allow for screw-motion placement. Four sheep of various ages were chosen from natural pasture farm with HACCP certificate and kept 30 days in controlled conditions with identical pasture prior to surgery. At the day of surgery three implants were epicrestally placed using regular implant surgical protocol in right tibia of each sheep 2cm apart. After 4, 8 and 12 weeks from each sheep one implant and the surrounding bone were removed by a 7mm diameter trephine bur, the samples prepared and histologically analyzed. All surgeries were performed in general anesthesia. After completion of the investigation sheep were healthy and in normal function. Results: Histological analyzes demonstrated formation of bone at the bone to implant contact. Time-related bone maturation was typical for dental implants. However, BIC at 12 weeks was more mature at Ti12Mg implants in comparison to the commercially available implant. Histomorphometric analysis showed average BIC values within the bone marrow at 4 weeks 52%, at 8 weeks 81% and at 12 weeks 96%. BIC values within the cortical bone were 59% at 4 weeks, 89% at 8 weeks and 98% at 12 weeks. No signs of gaseous enclosures were determined in the surrounding bone. Conclusions and clinical implications: Proposed Ti12Mg composite, with Mg phase acting as beneficiary modulator for generating an osseoconductive surface via spontaneous dilution in body environment as well as bone formation stimulant, suggests this material answers crucial demands for dental implants. Information concerning similar studies is scarce, and implant material where porous bioactive bimetallic composite is obtained with similar properties, has not so far been proposed.

Metallic implant materials are biomaterials that have experienced major development over the last fifty years, yet some demands posed to them have not been addressed. For the osseointegration process and the outcome of endosseous implantation, it is crucial to reduce the stress shielding effect and achieve sufficient biocompatibility. Powder metallurgy (PM) was utilized in this study to fabricate a new type of titanium (Ti) + magnesium (Mg) bioactive composite to enable stress-shielding reduction and obtain better biocompatibility compared with that of the traditional Ti and Ti alloys used for dental implants. Such composites are produced by well-known cost-effective and widely used PM methods, which eliminate the need for complex and costly Ti casting used in traditional implant production. The relation between the microstructure and mechanical properties of as-extruded Ti + (0–24) vol% Mg composites was investigated with respect to the Mg content. The microstructure of the composites consisted of a biodegradable Mg component in the form of filaments, elongated along the direction of extrusion, which were embedded within a permanent, bioinert Ti matrix. As the Mg content was increased, the discrete filaments became interconnected with each other and formed a continuous Mg network. Young's modulus (E) of the composites was reduced to 81 GPa, while other tensile mechanical properties were maintained at the values required for a dental implant material. The corrosion behavior of the Ti + Mg composites was studied during immersion in a Hank's balanced salt solution (HBSS) for up to 21 days. The elution of Mg pores formed at former Mg sites led to a further decrease of E to 74 GPa. The studied compositions showed that a new Ti + Mg metallic composite should be promising for load-bearing applications in endosseous dental implants in the future.

In this work Small Punch Test (SPT) was applied to study the mechanical behavior of ultrafine-grained Al- Al2O3metal matrix composites (MMCs) fabricated in situ via powder metallurgy route (HITEMAL®). Such MMCs show attractive mechanical properties, enhanced creep performance and increased thermal stability at elevated temperatures, not normally associated with service of conventional Al alloys, even after prolonged high temperature exposure. MMCs fabricated from two powders of different particle size (d50 = 8.9 and 1.2μm) were evaluated in the present work. SPT was performed at room temperature using disc-shaped specimens of 10 mm in diameter. The effect of the different disc thickness (0.4, 0.5 and 0.6 mm) on the load vs. displacement function was evaluated. The displacements monitored from top and bottom sites of the specimen varied during the course of the test. The discs deformed throughout the test by two plastic stages, typical for ductile materials. The relation between load-displacement and stress–strain tensile curves for both composites was analyzed. A drastic change of mechanical behavior between the green compact of cold pressed material and the hot forged material was detected. New methods of determination of a characteristic load PY, which represents a transition from elastic to plastic bending regime were presented and discussed. A relationship between PY and corresponding yield stress was studied for each composite material by a calculation of their respective correlation parameters. Keywords: Small punch test, powder metallurgy, yield strength, aluminum, composite, correlation parameter.

Ultrafine-grained (UFG) Al matrix composites reinforced with 15 and 30vol% in-situ Al3Ti filaments were fabricated by extrusion of Al-Ti powder mixtures followed by solid-state reactive diffusion. Fine Al powder particles (1.3μm) heavily deformed the coarser Ti particles (24.5μm) into filaments during extrusion. Upon a subsequent operation of hot isostatic pressing (HIP), the micrometric Al3Ti filaments elongated along the extrusion direction and formed in situ in the UFG Al matrix. Fabricated composites are free of pores and voids with perfect bonding created at the Al-Al3Ti interfaces. In parallel, a small portion (2.4vol%) of nanoscale γ-Al2O3 particles, which originate from native amorphous films on fine Al powders, formed in situ and were homogenously dispersed in the Al matrix. The microstructures of as-extruded and after HIP composites were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD). Owing to the presence of nanometric γ-Al2O3 particles with Al high angle grain boundaries (HAGBs), the UFG Al matrix remained stable even after HIP at 600°C for 9h. The mechanical properties and creep performance of composites at testing temperatures of up to 600°C were systematically studied. The Al-Al3Ti composites exhibited a combination of increased strength and Young's modulus in addition to excellent creep performance and structural stability, which indicates that the studied composites are potential structural materials capable of service at elevated temperatures. Fil: Krizik, Peter. Slovak Academy of Sciences; Eslovaquia Fil: Balog, Martin. Slovak Academy of Sciences; Eslovaquia Fil: Nosko, Martin. Slovak Academy of Sciences; Eslovaquia Fil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Dvorak, Jiri. Institute of Physics of Materials; República Checa Fil: Bajana, Oto. Slovak Academy of Sciences; Eslovaquia

In order to improve the Young’s modulus of Al–SiC composites, the matrix-reinforcement interface was modified via chemical reactions between the Al matrix and SiC particles. To prepare diverse interfaces, various types of composites were fabricated using the direct hot extrusion of Al-based powder mixtures containing 30 vol% untreated or oxidized SiC particles. The extruded composites were subjected to different annealing treatments. A detailed microstructural characterization of the Al–SiC interfacial regions was performed. The effect of the interface on the Young’s modulus and on the other mechanical properties of the composites was systematically investigated. Depending on the interface quality, the Young’s modulus of the composites can be varied over the range of 88–121 GPa. The results proved the importance of a stiff phase—comparable to SiC stiffness at the interface, which leads to the SiC particles contributing more effectively to the increase in the composite Young’s modulus. Conversely, the segregation of liberated Si at SiC interface led to decrease of composites Young’s modulus.

The oxidation behavior of gas-atomized Al and Al alloy powder green compacts during heating prior to hot extrusion compaction was studied at laboratory and industrial scales by TGA, DSC, DTA, EDX, TEM and XRD methods. The effect of the heating of green compacts on the mechanical properties of the powder-extruded samples was assessed. Significant oxidation of Al and Al alloy powder green compacts takes place in the solid state during heating in air. The onset and intensity of oxidation were affected by the Mg content, the surface area of the powder and the volume of the powder green compacts. An exothermic heat associated with the oxidation of Al and Al alloy powders resulted in intense overheating of bulky powder green compacts during heating in air. The samples extruded from the powder green compacts heated in air exhibited reduced strength. The loss in strength was especially pronounced in the case of Mg-containing Al alloy powders. Mg diffuses from a powder metallic core toward the native Al 2 O 3 surface layer present on as-atomized Al alloy powders; it reacts with oxygen present in air and in the Al 2 O 3 surface layer where the MgO phase forms, eventually resulting in the depletion of Mg from the powder core. Materials extruded from Al powders depleted of Mg do not exhibit effective Al-Mg solid solution strengthening or strengthening by Mg-containing precipitates. Economically viable approaches to avoiding the detrimental effects of powder oxidation during the heating of green compacts prior to hot working consolidation are discussed.

This paper reports the development of novel Sinter-Aluminum-Pulver (SAP)-like Al–AlN nanocomposites via replacing the native Al2O3 thin films on fine Al powder with a large volume fraction of in situ formed nanometric AlN dispersoids. Fine gas-atomized Al powder (d50=1.3 µm) compacts were first partially nitrided at 590 °C in flowing nitrogen, controlled by a small addition of Sn (0.3–0.4 wt%), and subsequently consolidated by hot direct extrusion. The resulting Al–AlN composites consisted of submicrometric Al grains reinforced with nanometric AlN dispersoids together with some nanometric Al2O3 dispersoids. An Al–13 vol% AlN nanocomposite fabricated this way achieved exceptional ultimate tensile strength of 227 MPa, yield strength of 195 MPa and Young's modulus of 66 GPa at 300 °C, superior to typical SAP materials and coarse grained Al–AlN composites. In addition, the Al–13 vol% AlN nanocomposite exhibited good thermal stability up to 500 °C. The strengthening mechanism is discussed.

This paper presents the warm pressing as an alternative powder metallurgy approach to conventional press-and-sinter or hot working (e.g., extrusion, forging) consolidations of Al powders into complex near-net-shape parts with required mechanical properties. In this study gas-atomized Al powders (A1050 and A6061) with various particle sizes were consolidated by uniaxial pressing, with minimum plastic deformation induced, at temperatures of 22 and 430 °C, respectively. The materials pressed at 22 °C showed poor strengths, ductility and electrical conductivity. The properties were improved markedly when pressing temperature increased to 430 °C and reached values comparable to A1050 and A6061 materials fabricated by conventional powder and ingot metallurgy approach. Similarly, the properties of the materials pressed at 22 °C were improved after annealing at 300 °C for 2 h. This indicated the formation of sufficiently strong interfacial bonding between native oxide layers on adjacent Al powder particles (i.e., grains) when processing temperature increased to 300 °C. With interfacial bonding established, the fracture mechanism changed from brittle to ductile character.

We report on the study on the titanium- magnesium (Ti–Mg) bioactive metal-metal composite utilized for a fabrication of dental implants. The biomedical Ti-12vol.%Mg composite, named BIACOM, is manufactured using a cost effective approach, where a mixture of elemental Ti and Mg powders is extruded at low temperature to sound profiles. Microstructure of composite comprises filaments of biodegradable Mg component, which are arrayed along extrusion direction and are homogenously distributed within permanent, bioinert Ti matrix. Compared to Ti Grade 4, the reference material used for dental implants, the properties of as-extruded composite include significantly reduced Young’s elastic modulus (92.1 GPa) and low density (4.12 g.cm −3 ), while the mechanical strength of Ti Grade 4 is maintained. Dynamic testing of dental implants fabricated from as-extruded com- posite, realized to follow the ISO 14801 standard for endosseous dental implants, confirms fatigue performance of BIACOM implants equal to the one of the reference material. Exposure of as-extruded composite samples to Hank’s solution, realized in order to simulate behavior in human body over the time after implan- tation, yields gradual dilution of Mg from composites surface and volume. Cor- roded Mg leaves at prior Mg filament sites pores within Ti matrix, which remains intact. This provides further decrease of Young’s modulus and enhances macro and micro roughness at implants surface. As a result, BIACOM shows improved mechanical compatibility (i.e., reduction of stress-shielding) and better osseointe- gration potential.

The rapidly solidified AlCr4.7Fe1.1Si0.3 (at.%) alloy produced at large scale by direct extrusion of gas atomised powders was investigated. Hot-extrusion yielded sound compacts and did not create any major structural changes compared to the as-atomised state. Microstructural characterisation of the as-extruded material revealed submicron scale α-Al grains with an embedded Al7Cr crystalline phase and traces of a nano-scale quasicrystalline Al84.6Cr15.4 phase. The long-term thermal stability up to 300 °C of compacts was proven. The thermal stability of compacts was accompanied by high mechanical properties, especially high strength and Young's modulus, and creep performance up to 300 °C. The same material was prepared by laboratory scale extrusion of cryo-chopped melt-spun ribbons as a reference material. No major differences in the structure or properties of the industrially prepared material were observed compared to the reference material.

Bulk Al materials with average grain sizes of 0.47 and 2.4μm, were fabricated by quasi-isostatic forging consolidation of two types of Al powders with average particle sizes of 1.3 and 8.9μm, respectively. By utilizing the native amorphous Al2O3 (am-Al2O3) film on the Al powders surfaces, a continuous, ~7nm thick, am-Al2O3 network was formed in situ in the Al specimens. Systematic investigation of the changes to the am-Al2O3 network embedded in the Al matrix upon heating and annealing up to 600°C was performed by transmission electron microscopy (TEM). At the same time, the stability of the Al grain structure was studied by transmission Kikuchi diffraction (TKD), electron back-scatter diffraction (EBSD), and TEM. The am-Al2O3 network remained stable after annealing at 400°C for 24h. In-situ TEM studies revealed that at temperatures ≥450°C, phase transformation of the am-Al2O3 network to crystalline γ-Al2O3 particles occurred. After annealing at 600°C for 24h the transformation was completed, whereby only nanometric γ-Al2O3 particles with an average size of 28nm resided on the high angle grain boundaries of Al. Due to the pinning effect of γ-Al2O3, the Al grain and subgrain structures remained unchanged during annealing up to 600°C for 24h. The effect of the am-Al2O3→γ-Al2O3 transformation on the mechanical properties of ultrafine- and fine-grained Al is discussed from the standpoint of the underlying mechanisms. Fil: Balog, Martin. Slovak Academy of Sciences; Eslovaquia. University of California at Davis; Estados Unidos Fil: Hu, Tao. University of California at Davis; Estados Unidos Fil: Krizik, Peter. Slovak Academy of Sciences; Eslovaquia Fil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Saller, Brandon D.. University of California at Davis; Estados Unidos Fil: Yang, Hanry. University of California at Davis; Estados Unidos Fil: Schoenung, Julie M.. University of California at Davis; Estados Unidos Fil: Lavernia, Enrique J.. University of California at Davis; Estados Unidos

Komercijalno čisti titanij (CP Ti) se koristi u dentalnoj medicini zbog biokompatibilnosti, dobrih mehaničkih svojstava i otpornosti na koroziju. Konvencionalni proizvodni procesi izrade takvog titanija mogu utjecati na kvalitetu površine uzoraka i rezultirati slabim vezanjem CP Ti s dentalnom keramikom. Zato se uvode nove tehnologije proizvodnje titanija, primjerice metalurgija praha i oblikovanje na erozimatu s žicom (WEDM). Svrha ovog istraživanja jest odrediti utjecaj WEDM-a na površinu uzoraka P/M CP Ti proizvedenih za ispitivanje vezne čvrstoće prema normi ISO 9693. Materijali i metode: Osam uzoraka P/M CP Ti dimenzija prema normi ISO 9693 proizvedeno je korištenjem WEDM-a i podijeljeno u dvije grupe – u neobrađene i brušene. Površine obje grupe uzoraka analizirane su metodama SEM, EDS i XDR. Rezultati: Analize neobrađenih uzoraka metodama SEM i EDS pokazuju tanki sloj različitog sastava i frakture. Brušeni uzorci imaju homogenu strukturu bez fraktura. Analiza metodom XDR pokazuje visoku koncentraciju titanijevih oksida na površini neobrađenih uzoraka, a nakon brušenja dobivena je samo čista α-faza. Zaključak: WEDM je metoda prikladna za proizvodnju uzoraka prema normi ISO 9693, ako se uzorci naknadno bruse., Purpose: Commercially pure titanium (CP Ti) has been recognized in dentistry for its biocompatibility, good mechanical properties and corrosion resistance. Conventional manufacturing processes can affect surface quality and result in poor bonding of dental ceramics to CP Ti. This is why powder metallurgy (P/M) and wire electro-discharge machining (WEDM) are being introduced in the manufacturing process. The aim of this study was to evaluate the effect of WEDM on the surface composition and microstructure of P/M CP Ti samples produced for bond strength testing according to ISO 9693. Materials and methods: Eight samples of P/M CP Ti, dimensions according to ISO 9693, were made using WEDM and divided in two groups (untreated and grinded). Microanalyses of chemical composition and microstructure of both groups were made using SEM, EDS and XDR. Results: SEM and EDS analysis of untreated samples showed a thin layer on surfaces with fractures in it. Grinded samples showed homogenous structure with no layer and no fractures. XDR analysis showed high level of oxides on the surface of untreated samples, while after grinding only pure α-phase was found. Conclusion: WEDM is a suitable method of sample production for ISO 9693 if accompanied by grinding with silicon carbide papers P320-P4000.