Values Of micro-Vickers Hardness Research Articles

3D Model of Bone Scaffolds Based on the Mechanical Behaviour for a Hybrid Nano Bio-composites

Ceramic/polymer Nano composites in the view of possessing design uniqueness and property combinations have gained a great attention and reported to be the materials of the 21st century that are not found in conventional composites. In the present work, an attempt has been made to study, develop and improve the bio-mechanic for a designed and fabricated Ceramic/polymer bio-composite for a human natural bone repair and replacement in the case of complex fracture and bone diseases by adding the Nano fillers ceramic particles to the Polymer Matrix Nano composites (PMNC) for fabricated a hybrid Titanium dioxide and yttria stabilized zirconia reinforced high density polyethylene (HDPE) matrix bio-composites properties. These bioactive composites have been investigated by using hot pressing technique at different compression pressures of (30, 60, and 90 MPa) at a compounding temperature of (180, 190, and 200 °C). The SOLIDWORKS 17.0 and the finite element ANSYS 15.7 software programs were used to the simulation, modelling and analysing of femur bone biomechanics that can withstand the highest stresses and strains. The response surface methodology (RSM) technique was used to improve and verify the results. For all the fabricated Nano bio-composites systems, the results showed that the obtained output parameters values were increased with increasing the process input parameters, also the vice versa for the strain energy and equivalent elastic strain values, also the Nano ceramic compositions represented the main factor influenced the results. The main investigates results of the current research deduced that for the increase of the Nano ceramic powder (TiO2) contain from 1% to 10%, the compression fracture strength and the micro-Vickers hardness values increased by 50% and by 8.45%, respectively, and when adding 2% of zirconia (ZrO2), an additional increase in the compression fracture strength and micro hardness by 28.21% and 40.19% achieved, respectively. When using 10% TiO2 + 2% ZrO2/HDPE bio-composite at highest compact temperature of 200 °C and compounding pressure of 90 MPa, the strain energy and the equivalent elastic strain reduced by 82.69% and 14.53% when compared with using of 1% TiO2 content. While when increasing the nano ceramic content from 1% to 10% without adding the ZrO2 nano filler, they reduced by 142.25% and 67.81%, respectively. The maximum equivalent von Misses stress obtained is equal to 39.957MPa and when increasing the nano ceramic content from 1% to 10%, the stress safety factors and fatigue live values increased by 58.38% and by 46.28%, respectively and when adding 2% of zirconia (ZrO2), the stress safety factor reached its maximum values, with an additional increase in its values by 21.42% and 69.40%, respectively. These results give great choices to use successful in vivo tests and for a better life performance with any age, patient status and degree of injury.

Effect of manganese bands on austenite formation of low carbon steels in dual phase steel manufacture

A model has been developed to predict the heating rates required to obtain a specific amount of overlap between ferrite recrystallization and austenite formation in the heating step of dual phase steel manufacture. The predicted heating rates of 0.2, 7, 50.5 and 511 0C/s were employed to heat the initial hot rolled steels to inter-critical temperature of 750 0C for 60 sec followed by quenching to room temperature. The effect of manganese bands on the variation of through thickness austenite formation was systematically evaluated in this study. The Mn band spacing of the initial hot rolled samples was found to be 18.5 µm. Thermo-Calc simulations showed that the equilibrium austenite start temperature of the Mn enriched region is at least 70 0C lower than the average composition. This variation in the composition and its corresponding austenite start temperature led to the formation of significant band structure of martensite at centre and random distribution at surface for all the heat-treated samples. Due to this, the micro-Vickers hardness values show significant through thickness anisotropy in all the samples. Moreover, with the increase in heating rates the potential nucleating sites of austenite decreased which led to the formation of thicker bands in the samples heat-treated at higher heating rates.

Effect of Plasma Ion Nitriding Temperature on the Durability of SCM440 Steel

In this study, plasma ion nitriding technology was applied to investigate the effect of plasma ion nitriding temperature and the surface roughness of SCM440 steel on the durability of SCM440 steel for gear material. The mechanical properties of the plasma ion nitrided specimens were examined using a comprehensive analysis of nitriding depth, phase change, microstructure and micro-Vickers hardness values. As a result, the durability of SCM440 steel was found to be more significantly affected by plasma ion nitriding temperature than surface roughness. As the plasma ion nitriding temperature increased, the composite phase of brittle γ’- Fe4N + ε-Fe2-3N was converted into a single phase of γ’-Fe4N, and the depth of the nitride layer increased, making it suitable for gear materials. Key words: Plasma ion nitriding, SCM440 steel, Durability, Gear

Crystal Growth and Physical Properties of Lu(Al<sub>1-x</sub><i>T</i><sub>x</sub>)B<sub>4</sub> (<i>T</i> = Fe, Cr) by Al-Self Flux

Crystals of the quaternary compounds α-Lu(Al1-xTx)B4(T = Fe, Cr) (YCrB4-type, orthorhombic, Pbam), obtained from the nominal composition of Lu(Al1-xTx)B3, were grown by using Al flux mixed with T metal at 1773 K for 5 h under an Ar atmosphere. The maximum dimensions and morphology of the crystals obtained were about 0.7 mm × 0.5 mm for flake-type crystals of Lu(Al1-xCrx)B4and about 5.2 mm × 0.2 mm for prism crystals of Lu(Al1-xFex)B4. The lattice constants determination and chemical analyses of Lu(Al1-xTx)B4(T = Fe, Cr) compounds were carried out for Fe 0.5 - 10.0 at% and Cr 0.5 - 1.0 at%. The lattice constants and the unit lattice volume in Lu(Al1-xTx)B4crystals decreased with increase of the concentration of Fe or Cr. The values of micro-Vickers hardness of Lu(Al1-xFex)B4(x = 0.005 - 0.030) and Lu(Al1-xCrx)B4(x = 0.005 - 0.010) samples are in the ranges of 16(2) - 20(3) GPa and 13(2) - 16(3) GPa, respectively. The hardness values showed a little increase as the solid solution of Fe or Cr was realized in Lu(Al1-xTx)B4, possibly because of distortion to the crystal structure. The magnetic susceptibility of as-grown Lu(Al0.995Fe0.005)B4crystals for example, exhibited diamagnetic behavior with a small ferromagnetic component.

Hydroxyapatite-Zirconia Composite Thin Films Showing ImprovedMechanical Properties and Bioactivity

Nano-crystalline hydroxyapatite (HAp) films were formed at the Ti surface by a single-step microarc oxidation (MAO), and HAp-zirconia composite (HZC) films were obtained by subsequent chemical vapor deposition (CVD) of zirconia onto the HAp. Through the CVD process, zero- and one-dimensional zirconia nanostructures having tetragonal crystallinity (t-ZrO2) were uniformly distributed and well incorporated into the HAp crystal matrix to form nanoscale composites. In particular, (t-<TEX>$ZrO_2$</TEX>) was synthesized at a very low temperature. The HZC films did not show secondary phases such as tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) at relatively high temperatures. The most likely mechanism for the formation of the t-<TEX>$ZrO_2$</TEX> and the pure HAp at the low processing temperature was proposed to be the diffusion of <TEX>$Ca^{2+}$</TEX> ions. The HZC films showed increasing micro-Vickers hardness values with increases in the t-<TEX>$ZrO_2$</TEX> content. The morphological features and phase compositions of the HZC films showed strong dependence on the time and temperature of the CVD process. Furthermore, they showed enhanced cell proliferation compared to the <TEX>$TiO_2$</TEX> and HAp films most likely due to the surface structure change.

Characteristics of TiAlN Film on Different Buffer Layer byD.C Magnetron Sputter

TiAlN films were deposited on WC-5Co substrates with different buffer layers by D.C. magnetron sputtering. The films were evaluated by microstructural observations and measuring of preferred orientation, hardness value, and adhesion force. As a process variable, various buffer layers were used such as TiAlN single layer, TiAlN/TiAl, TiAlN/TiN and TiAlN/CrN. TiAlN coating layer showed columnar structures which grew up at a right angle to the substrates. The thickness of the TiAlN coating layer was about <TEX>$1.8{\mu}m$</TEX>, which was formed for 200 minutes at <TEX>$300^{\circ}$</TEX>. XRD analysis showed that the preferred orientation of TiAlN layer with TiN buffer layer was (111) and (200), and the specimens of TiAlN/TiAl, TiAlN/CrN, TiAlN single layer have preferred orientation of (111), respectively. TiAlN single layer and TiAlN/TiAl showed good adhesion properties, showing an over 80N adhesion force, while TiAlN/TiN film showed approximately 13N and the TiAlN/CrN was the worst case, in which the layer was destroyed because of high internal residual stress. The value of micro vickers hardness of the TiAlN single layer, TiAlN/TiAl and TiAlN/TiN layers were 2711, 2548 and 2461 Hv, respectively.

Crystal Growth of Aluminum Magnesium Borides from Al-Mg-B Ternary System Solutions and Properties of the Crystals

Single crystals of AlMgB14and AlMgB22were grown from a high-temperature aluminum metal flux in an Ar atmosphere. The optimum conditions for growing AlMgB22and AlMgB14were established using the starting mixtures of B/Mg=0.5-1.0 and B/Mg=2.0-6.0. The AlMgB14and AlMgB22crystals obtained have well-developed {001} and {100} faces, and were black with a metallic luster. The maximum dimensions of these crystals were about 5.2 mm and 4.6 mm, respectively. The values of micro-Vickers hardness of the AlMgB14and AlMgB22crystals are in the ranges of 23.9±0.6-27.6±0.6 GPa. The oxidation process of AlMgB14and AlMgB22crystals were studied up to 1473 K by TG-DTA method. The susceptibility of AlMgB14 with an increase at low temperatures does not show any particular features, being indicative of a paramagnetic contribution, which is likely due to impurities. The susceptibility of the AlMgB22sample shows no apparent contribution from impurities and also does not have any anomalous behavior.

Microstructural analysis and mechanical properties of in situ Nb/Nb-aluminide layered materials

Thin foil hot press process has been developed for manufacturing metal/intermetallic compound laminate composites to induce self-propagating high-temperature synthesis (SHS) reaction between different pure metal sheets. In the present work, Nb/Nb-aluminide laminate composites were manufactured with pure Nb and Al sheets, which consist of fine Nb/Nb2Al/NbAl3 or Nb/Nb3Al/Nb2Al/NbAl3 layer structure. Microvickers hardness test and energy dispersive X-ray spectroscopy (EDS) analysis in the intermetallic compound layer demonstrate the formation of various phases, and the microvickers hardness values decrease with increasing Al/Nb atomic ratio. Although the tensile strength of laminate composites is similar to pure Nb, ductility and fracture toughness are significantly improved due to plastic deformation in Nb layer.

Mechanical properties of (U,Ce)O 2 with and without Nd or Zr

The mechanical properties of (U 0.8− x Ce 0.2M x )O 2 [M: Nd (0≤ x≤0.13) or Zr (0≤ x≤0.06)] were studied. The longitudinal and shear sound velocities were measured by an ultrasonic pulse–echo method at room temperature, which enabled us to evaluate the elastic properties and Debye temperature. The microhardness measurement was performed at room temperature using a micro-Vickers hardness tester. The elastic moduli such as Young’s modulus and shear modulus decrease with increasing M atoms content. The values of micro-Vickers hardness and yield stress also decrease with increasing M atoms content.

Wear mechanism of stainless steel confirmed by applications of phase-transformation of itself and CCD camera

For the combination of three kinds of diamond sliders with various tip radii and the stainless steel (SUS 304) disks with phase-transformation properties, wear test was carried out under unlubricated condition at a sliding speed of 48–59 mm/s, and under load ranges of 0.5–2.0 N. The measurement of the displacement due to magnetic force generated by frictional force, the topographical analysis, and the observation made by using CCD camera were carried out and compared with the specific wear rates of the stainless steel disk to make the wear process of metals clear. As a result, the following observations were found: (a) the weak parts on the pile-up ridges and the protuberances stretched by plastic flow were removed as wear debris particles beyond their endurance limits; (b) the specific wear rates were detected at the critical displacement φ c due to magnetic force which were approximately constant regardless of a normal load; (c) the degree of plastic deformation of asperities and their anti-wear properties in the mild contact stress range would be able to be estimated from the displacement φ e in the steady state than from the micro-Vickers hardness values (HV).

Chemical State and Properties of the New Layer Structure Compound PrRh4.8B2 Single Crystals Obtained by Molten Metal Flux Method Using Cu as Solvent.

A new layer structure compound PrRh4.8B2 was obtained by a molten metal flux growth method, using Cu as a flux. This compound belongs to the orthorhombic system with the space group Fmmm. Lattice parameters were a=0.9697(4)nm, b=0.5577(2)nm and c=2.564(3)nm. The structure of the compound is of a modified CeCo3B2-type, which is explained by a stacking model of Pr-B and rhodium layers. X-ray photoelectron spectra were taken under three conditions: (i) surface of fractured in the vacuum of the spectrometer; (ii) surface exposed to air after fracture in the spectrometer; and, (iii) surface fractured in air. The X-ray photoelectron spectroscopic study and electron probe micro-analysis results show that a few monolayers of Cu atoms exist between the crystals of PrRh4.8B2. The thermo-gravimetric curve shows that oxidation of the PrRh4.8B2 proceeds above 873K. Weight gain of the specimen heated up to 1473K in air is 13.44%. Sample forms PrBO3 and Rh as a result of the oxidation. The temperature dependence of the inverse static magnetic susceptibility χ-1 obeys the Curie-Weiss law at temperatures above 50K. The magnetic moment μeff is 4.2μB and the Curie-Weiss temperature Θp is-13K. The value of micro Vickers hardness for c-plane with the orthorhombic symmetry of PrRh4.8B2 is 6.7±0.6GPa.

Dynamic consolidation of superhard materials

Shock consolidation experiments were conducted via flyer impact on synthetic diamond (6–12 μm) and cubic boron nitride (c-BN) (4–8 μm) admixed with SiC whisker (SCW), Si3N4 whisker (SNW), SiC powder, and Si powder contained in stainless steel capsules under the shock pressure range of 10–30 GPa. Scanning electron microscopy and transmission electron microscopy imaging of the samples revealed no plastic deformation or melting of diamond and virtually no deformation of c-BN, whereas the SCW and SNW were extensively melted and recrystallized into bundle-shaped crystallites. In contrast, SiC powder mixed with diamond was also melted but demonstrated equant grain growth. A new method to calculate the shock temperature and melt fraction is formulated on the basis of Milewski's sphere-rod packing data. The new method assigns excess bulk volume to the zone around whiskers and yields a better description of the energy deposition mechanism of the consolidation of powder-whisker systems. Some of the experiments employed Sawaoka's post-shock annealing technique, in which the sample is sandwiched between two layers of a mixture of titanium powder plus carbon. Very well consolidated samples were obtained with post-shock heating under shock pressures of only about 11 GPa. Micro-Vickers hardness values up to 27 GPa were obtained for c-BN plus SCW at a low impact velocity of 1.45 km/s with post-shock heating. This hardness is similar to that obtained at a higher impact velocity of 1.95 km/s without post-shock heating. To understand the post-shock heating process, one-dimensional time dependent temperature profile calculations were conducted for the sample and Ti + C layers. Post-shock heating appears to be very important in the consolidation of powder and whisker admixture. The calculated optimum Ti + C thickness is about 0.8–1.7 mm at a porosity of 40% for a typical sample thickness of 2 mm. The heating and cooling time is a few milliseconds. Good compacts with micro-Vickers hardness values up to 28 GPa were also obtained upon shock consolidation of diamond plus Si admixtures.

メカニカルアロイングを応用したＮｂＣ分散強化鉄粉の作製

Mechanical alloying was carried out using pure iron, pure niobium and graphite powders. The very fine homogeneous alloy powder was obtained after the mechanical alloying for 144.0 ks. The very fine NbC particles were precipitated in this alloy powder by the heat-treatment in the temperature range of 873-1273 K. The mean particle size of the NbC was decreased with decreasing the heat-treatment temperature, resulting in about 8.5 nm by the heat-treatment at 873 K for 3.6 ks. The mean particle size of the NbC precipitated by the present method was finer than that of the NbC powder using as starting materials crushed and dispersed by mechanical alloying. The micro-Vickers hardness values were very high in the lower temperature range, however they were decreased with increasing the heat-treatment temperature.

Dynamic consolidation of cubic boron nitride and its admixtures

Cubic boron nitride (C–BN)' powders admixed with graphite-structured boron nitride powder (g-DN), silicon carbide whisker (SCW), or silicon nitride whisker (SNW) were shock compacted to pressures up to 22 GPa. Unlike previous work with diamond and graphite [D. K. Potter and T. J. Ahrens, J. Appl. Phys. 63, 910 (1987) it was found that the addition of g-BN inhibited dynamic consolidation. Good consolidation was achieved with a 4–8 μm particle size C–BN powder admixed with 15 wt.% SNW or 20 wt.% SCW whereas a 37–44 μm particle size C–BN mixture was only poorly consolidated. Scanning electron microscopy (SEM) analysis demonstrates that SCW and SNW in the mixtures were highly deformed and indicated melt textures. A skin heating model was used to describe the physics of consolidation. Model calculations are consistent with SEM analysis images that indicate plastic deformation of SCW and SNW. Micro-Vickers hardness values as high as 50 GPa were obtained for consolidated C–BN and SNW mixtures. This compares to 21 GPa for single-crystal Al2O3 and 120 GPa for diamond.

シリコンナイトライド膜へのカーボン添加

Some of the optical and mechanical properties of carbon incorporated amorphous silicon nitride films prepared by rf magnetron sputtering were examined. Silicon was sputtered by an Ar+H2 gas mixture, nitrogen and carbon were introduced by the decomposition of NH3 and CH4 gases respectively. Various properties of the films such as composition, infrared absorption, visible and ultraviolet absorption, microvickers hardness and internal stress were measured. Optical band gap was increased from 1.5 to 5.0 eV in proportion to the N content and was barely affected by the addition of carbon. The maximum value of microvickers hardness obtained was about 4200 kg/mm2 in Si0.4N0.6; H film, and, at the most, decreased by about 20% with the addition of carbon. Internal stress was compressive in all films and increased up to 7.3×109 dyne/cm2 in SiNx; H films in proportion to nitrogen content. By addition of carbon, stress decreased to less than one half of that of carbon free films.