http://research.me.udel.edu/~dlburris/papers/JA27.pdf

A quantitative method for measuring nanocomposite dispersion

Potential and challenges of metal-matrix-composites reinforced with carbon nanofibers and carbon nanotubes

Local deformation and damage mechanisms have been studied for a commercial DP600 steel using in-situ tensile testing inside a scanning electron microscope (SEM) in combination with Digital Image Correlation (DIC). Different gauge geometries have been used to study damage evolution processes during tensile testing up to final failure. Strain distributions have been measured within the ferrite and martensite phases, together with the corresponding strain values for identified damage initiation mechanisms. According to the strain maps, large plastic deformation with strain values as large as 4.5 have been measured within the ferrite phase. Severe deformation localization and slip band formation were observed within the ferrite grains. The DIC results show that martensite in the studied material is plastically deformable with a heterogeneous strain distribution within the islands with values of up to 0.9 close to the phase boundaries. Failure of the martensite islands occurs mostly due to micro-crack initiation at the boundaries with the ferrite followed by crack propagation towards the centre of the islands. As for the ferrite matrix, it is found that its interface with the martensite is strong and cohesive. Localized damage in the matrix occurs by sub-micron void formation within the ferrite adjacent to the interface as opposed to the separation along the phase boundary itself or in the central regions of the ferrite grains A mechanism has been proposed to explain the deformation and damage evolution in the microstructure of the studied DP600 steel up to the final fracture.

/pdf/failure-mechanisms-in-dp600-steel-initiation-evolution-and-20oikp7cmb.pdf

Failure mechanisms in DP600 steel: Initiation, evolution and fracture

Nanoscale segregation behavior and high-temperature stability of nanocrystalline W-20 at.% Ti

Multilayer DLC coatings via alternating bias during magnetron sputtering

a b s t r a c t 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 -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 prop- erties, 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.

Materials Science and Engineering A

Otpuštanje iona titanija iz inovativnog titanij-magnezijeva kompozita: istraživanje in vitro Titanium Ions Release from an Innovative Titanium-Magnesium Composite: an in Vitro Study

Background: Magnesium enhances osteoinduction, osteoconduction and osseointegration of implanted material by interacting in important intra- and intercellular osteogenic processes in the alveolar bone during a new, perimplant bone formation. However, because of its poor corrosion resistance and high chemical reactivity, it can not be used as a pure magnesium. Powder metallurgy technique is one of possible production strategy how to incorporate magnesium in titanium matrix. In that way produced, innovative titanium- magnesium composite material can develop a biologically inspired titanium- based surface by releasing magnesium, increasing porosity and developing a favorable surface chemistry in order to improve the process of osseointegration. Aim: The aim of the present study is to quantify the amount of in vitro released magnesium from the surface of an innovative titanium- magnesium composite material and to determine physical properties and the chemistry of the surface after 42 days of immersion in simulated body fluid. Material and methods: Two groups of experimental innovative titanium-magnesium composite were produced by means of powder metallurgy technique: 1 mass% of magnesium in titanium matrix and 2 mass% of magnesium in titanium matrix. Specimens were prepared using standard metallographic methods, ground and polished. In vitro static immersion test was performed for 42 days using Hank’s balanced salt solution as a simulated body fluid at 37 oC in thermostat. The test was carried out in triplicates. The blank test solutions were set and treated in identical manner. The mass concentration of released magnesium ions in the simulated body fluid was measured using inductively coupled plasma mass spectrometry and the amount of released magnesium per cm2 of tested surface was calculated from obtained data. The surface topography was observed by means of scanning electron microscopy using back- scattered electron and secondary electron detectors at the magnification of 50 and 200 times and the electron beam acceleration voltage of 20 kV. Energy dispersive spectroscopy was used in order to determine the chemical microanalysis of the surface. X-ray diffraction analysis was performed for identification of crystal phases formed on the surface after immersion time. Basic statistic method was used to find mean value and standard deviations of the amount of released magnesium. The difference between the tested groups was evaluated by means of Student-t statistical test. Results: Mean value for the amount of the released magnesium after 42 days of immersion in Hank’s balanced salt solution from the material with 1 mass% of magnesium was 448.66 ± 23.42 μg/cm2 and from the material with 2 mass% magnesium was 503.11 ± 18.92 μg/cm2. Student t statistical test showed that there wasn’t statistical significant difference (p<0.05) between the amount of released magnesium from two tested materials and p value was 0.124878. Scanning electron micrographs at the magnification of 50 and 200 times using secondary electron detector showed homogeneously distributed micropores and back- scattered electron detector clearly visualized dual chemical composition. By means of energy dispersive spectroscopy atoms of Mg and O, besides those of Ti, on the surface, were identified predominantly. X-ray diffraction analysis revealed formation of MgO crystals on the surface during the immersion time. Conclusions and clinical implications: Based on the in vitro study performed, one can conclude that magnesium can be released from innovative titanium- magnesium composite in surrounding area resulting in a porous surface topography and forming of MgO crystals on the surface. Such an effect may induce a favorable biological effect during the process of osseointegration of implants made of tested material. To determine the biological effect of releasing of magnesium in vivo, further research is needed.

The effect of magnesium on the development of biologically inspired titanium-based surface produced by powder metallurgy technique

Adresa za dopisivanje Prof.dr.sc. Ketij Mehulic Sveuciliste u Zagrebu Stomatoloski fakultet Gunduliceva 5 10 000 Zagreb Tel. 4802 111 mehulic@sfzg.hr Sažetak Komercijalno cisti titanij (CP Ti) se koristi u dentalnoj medicini zbog biokompatibilnosti, dobrih mehanickih svojstava i otpornosti na koroziju. Konvencionalni proizvodni procesi izrade takvog titanija mogu utjecati na kvalitetu povrsine 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 povrsinu uzoraka P/M CP Ti proizvedenih za ispitivanje vezne cvrstoce prema normi ISO 9693. Materijali i metode: Osam uzoraka P/M CP Ti dimenzija prema normi ISO 9693 proizvedeno je koristenjem WEDM-a i podijeljeno u dvije grupe – u neobrađene i brusene. Povrsine obje grupe uzoraka analizirane su metodama SEM, EDS i XDR. Rezultati: Analize neobrađenih uzoraka metodama SEM i EDS pokazuju tanki sloj razlicitog sastava i frakture. Bruseni uzorci imaju homogenu strukturu bez fraktura. Analiza metodom XDR pokazuje visoku koncentraciju titanijevih oksida na povrsini neobrađenih uzoraka, a nakon brusenja dobivena je samo cista α-faza. Zakljucak: WEDM je metoda prikladna za proizvodnju uzoraka prema normi ISO 9693, ako se uzorci naknadno bruse. Kljucne rijeci titanij; erozimati sa žicom; vezna cvrstoca; metalurgija praha; svojstva povrsina 1 Sveuciliste u Zagrebu Stomatoloski fakultet School of Dental Medicine University of Zagreb 2 Sveuciliste u Zagrebu Fakultet strojarstva I brodogradnje Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb 3 Institut za materijale i strojarstvo, Slovacka akademija znanosti Institute of materials and machine mechanics, Slovak academy of sciences 4 Institut “Ruđer Boskovic”, Zagreb Institute “Ruđer Boskovic”, Zagreb

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Utjecajobradeerozimatomnamikrostrukturupovršinetitanija dobivenumetalurgijompraha Effects of Wire EDM on the Microstructure of P/M Titanium Samples

La presente invention concerne un procede de fabrication d'un composite a matrice metallique aluminium/alumine de taille nanometrique et une composition produite a partir de celui-ci. Le procede est caracterise en ce qu'il fournit une poudre d'aluminium ayant une couche de formation d'un oxyde naturel et une teneur en oxyde d'aluminium entre environ 0,1 et environ 4,5 % en poids et une surface specifique allant d'environ 0,3 a environ 5,0 m2/g, le travail a chaud de la poudre d'aluminium, et la formation d'un alliage d'aluminium a matrice grenee superfine. Il se forme alors simultanement in situ une distribution essentiellement uniforme de particules d'alumine de taille nanometrique. L'alliage presente un profil de proprietes/temperature essentiellement lineaire, de sorte que les proprietes physiques telles que la resistance sont essentiellement maintenues meme a des temperatures de 250 °C et plus.

Martin Balog

Papers

Materials Science and Engineering A

Otpuštanje iona titanija iz inovativnog titanij-magnezijeva kompozita: istraživanje in vitro Titanium Ions Release from an Innovative Titanium-Magnesium Composite: an in Vitro Study

The effect of magnesium on the development of biologically inspired titanium-based surface produced by powder metallurgy technique

Utjecajobradeerozimatomnamikrostrukturupovršinetitanija dobivenumetalurgijompraha Effects of Wire EDM on the Microstructure of P/M Titanium Samples

Alliage d'aluminium de type nanocomposite à température élevée et son procédé de fabrication