Search

The aim of this work was to study the effect of milling time on binary magnesium-titanium (Mg-Ti) alloy synthesized by mechanical alloying. A powder mixture of Mg and Ti with the composition of Mg-15wt%Ti was milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Milling process was carried out at 400 rpm for various milling time of 2, 5, 10, 15 and 30 hours. 3% n-heptane solution was added prior to milling process to avoid excessive cold welding of the powder. Then, as-milled powder was compacted under 400 MPa and sintered in a tube furnace at 500 °C in argon flow. The refinement analysis of the x-ray diffraction patterns shows the presence of Mg-Ti solid solution when Mg-Ti powder was mechanically milled for 15 hours and further. Enhancements of Mg-Ti phase formation with a reduction in Mg crystallite size were observed with the increase in milling time. A prolonged milling time has increased the density and hardness of the sintered Mg-Ti alloy.

The paper presents experimental results regarding the evolution of hardness and impact energy of some sintered steels alloyed with 1.5% respective 3% (weight) copper powders. For the experimental research were used 3 mixtures: Fe+0.2C as reference, Fe+0.2C+1.5Cu, Fe+0.2C+3Cu. All the samples were die pressed at three pressures 400, 500 and 600 MPa and were subjected at three types of treatments as following: SINT, SINTCARB and CARBSINT. For the sintering treatments was used argon atmosphere and for carburizing process was used methane. After each treatment the hardness and impact energy for all the samples were measured and were made correlations between these properties and the type of treatment and copper content.

The SmCo5has three sintering stages using spheres (0.6 – 1.0 mm diameter) at temperatures between 1030 and 1200 °C. During the first stage the neck radius increases as X2~ t for less than 1200 °C temperature, the exponent is 3 at 1200 °C. Interdiffusion is sintering mechanism for exponent of 2. Sm diffuses from inside to the surface, where it is oxidized and oxides fills the neck between the spheres. Co diffuses through the oxides. At 1200 °C the sintering mechanism is evaporation-condensation of Sm. The activation enthalpy of the first stage is 582 kJmol-1for temperatures above 1130 °C and 210 kJmol-1bellow 1130 °C, respectively. The second stage is characterized by a plateau where the neck growth is arrested. The small pores in the neck and in the sphere surface layer (formed during the first stage) shrink. When these pores disappear a continuous α-Co layer forms and the third stage starts. It is essential growth of the neck formed by dense Co layer. The law of sintering is X4~ t. The activation enthalpy (276 kJmol-1at temperatures above 1130 °C) closes the activation enthalpy of Co self-diffusion. This (together with the exponent of 4) suggests that the Co layer plays a role similar to that of a liquid film. Making slight changes in the chemical composition of the alloys and substituting an argon atmosphere to vacuum have no influence or stages and sintering mechanisms.

Mechanical alloying (MA) is used to prepare amorphous alloy powders. The experiments were performed by a high energy ball milling device using stainless steel vessels and balls under argon atmosphere at a rotation rate of 450 r/min. B and Y were used as the minor additions to prepare new quaternary or complex amorphous alloy powders. Ti50Al(47-x-y)Zr3BxYy(x=0, 0.6, y=0, 0.2) amorphous alloy powders were successively obtained. The milled amorphous alloy powders were characterized by XRD, SEM and DSC. Ti50Al47Zr3amorphous alloy powders were obtained after milled 50h. The milling time needed to obtain complete amorphous alloy for Ti50Al46.4Zr3B0.6, Ti50Al46.8Zr3Y0.2and Ti50Al46.2Zr3B0.6Y0.2are 40h, 35h and 30h, respectively. Minor additions of B and Y decreases the milling time for preparing amorphous alloy. SEM shows that B and Y can refine the grain of the amorphous alloy powders. DSC shows that minor substitution of 0.6at.%B or 0.2at.%Y can increase the glass forming ability (GFA) for the TiAl based alloys.

Zirconium diboride (ZrB2) powders were synthesized by sol-gel carbonthermal reduction method using zirconium oxychloride (ZrOCl2·8H2O), boric acid (H3BO3), source (C12H22O11) and citrate (as chelation agent). The Zirconium diboride precursors were calcined at 1600¡æ for 2h, 3h and 4h under argon atmosphere. The precursors and sintered samples were characterized by TG-DSC, XRD and SEM. Results revealed that the ZrB2powders prepared at 1600°C for 4h exhibited quasi-tabular morphology with a small average crystalline size about 20μ. With respect to the conventional solid state method, the Sol-gel method route guaranteed a faster, easier and energy-saving process for obtaining nanopowders.

The plasmodynamic synthesis was conducted in the electric hypervelocity pulse jet of carbon-silicon electric discharge plasma influenced on a copper target in an argon atmosphere. Some samples of a powder product with a high content of β-SiC were produced. The results of the experiments made at different levels of supplied energy were compared. It was shown that the sizes of crystals grew, when the energy of a plasma shot increased.

Ti-Fe alloy is prepared by the electrolytic reduction of titanium concentrate in molten CaCl2 under argon atmosphere. The formation mechanism of Ti-Fe alloy is discussed. The impact of electrolytic time on product is studied when electrolytic voltage is 3.1V and electrolytic temperature is 900°C. Results show that Ti-Fe alloy with uniform composition can be obtained by this method. The deoxidize product is iron and TiFe alloy by order. The reduction of Ti is a multi-step process and the intermediate products include CaTiO3,TiO2, Ti2O3, TiO,Fe, TiFe2.

The Al2M3Y(M=Cu, Ni) compound was synthesized by arc melting under argon atmosphere. The high-quality powder X-ray diffraction data of Al2M3Y have been presented. The refinement of the X-ray diffraction patterns for the Al2M3Y compound show that the Al2M3Y has hexagonal structure, space groupP6/mmm(No.191), with a = b = 5.1618(2) Å, c = 4.1434(1) Å,V= 95.6 Å3,Z= 1,ڑx= 5.7922 g/cm3,F30= 155.5(0.0057, 34), RIR = 2.31 for Al2Cu3Y, and with a = b = 5.0399(1) Å, c = 4.0726(1) Å,V= 89.59 Å3,Z= 1,ڑx= 5.9118 g/cm3,F30= 135.7(0.0072, 30), RIR = 2.54 for Al2Ni3Y.

New titanium alloys for biomedical applications have been developed primarily with the addition of Nb, Ta, Mo, and Zr, because those elements stabilize the β phase and they don’t cause cytotoxicity in the organism. The objective of this paper is to analyze the effect of molybdenum on the structure, microstructure, and selected mechanical properties of Ti-15Zr-xMo (x = 5, 10, 15, and 20 wt%) alloys. The samples were produced in an arc-melting furnace with inert argon atmosphere, and they were hot-rolled and homogenized. The samples were characterized using chemical, structural, and microstructural analysis. The mechanical analysis was made using Vickers microhardness and Young’s modulus measurements. The compositions of the alloys were sensitive to the molybdenum concentration, indicating the presence of α’+α”+β phases in the Ti-15Zr-5Mo alloy, α”+β in the Ti-15Zr-10Mo alloy, and β phase in the Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys. The mechanical properties showed favorable values for biomedical application in the alloys presenting high hardness and low Young’s modulus compared with CP-Ti.

The Mg2Si compound was synthesized by the solid state reaction method. The powder precursors of Mg and Si were thoroughly mixed in ballmilling for 24 hr in an argon atmosphere. Mixed powder was pressed at 170MPa and sintered at 800 °C for 6 hr in an argon atmosphere. The sinter powder was crushed in mortar for 1 hr. The crystal structure and microstructure were measured and observed by using XRD and SEM. The microstructure and the crystal structure were analyzed. TheMg2Si shows single phase, cubic structure and particle size about 1-10 mm.

F-75 (Co-Cr-Mo) alloy are widely used in the production of medical implants because of their excellent strength properties, hardness and also one of the biocompatible materials that very suitable in human body environment. In this research, the effect of sintering in terms of sintering temperature and sintering time has been studied by focusing on the microstructure, physical and mechanical properties of F-75 alloy. The samples were prepared by blending the starting material at 160 rpm for 30 minutes, uniaxially pressing at 500 MPa and sintering in an argon atmosphere at two sintering temperatures (1300°C and 1350°C) for four sintering times (60, 90, 120 and 150 minutes). The results show that the grains and bulk density increased with the increasing of sintering temperature and sintering times. However, opposite results were obtained for apparent porosity, hardness and compressive strength

Four high-entropy alloys are prepared by an arc furnace under argon atmosphere. The microstructure and the properties of the alloys are investigated. The results show that NiCrCuCoFe alloy consists of a single FCC solid solution. When Al presents in the alloys, the microstructures of the alloys change to a BCC+ FCC solid solution. It is indicated that Al element promotes the formation of BCC solid solution, and Si and Mn promote the formation of complicated compounds. The hardness of alloys with BCC structure is higher than that of the alloys with FCC structure. The complicated compounds are formed, the hardness increases further. The highest hardness of the alloys reaches 882 HV due to the strengthening of the second phase precipitation.

ZrB2-SiC ceramic composites with the addition of carbon black were fabricated by hot pressed sintering at 1900 °C for 60 min at a uniaxial pressure of 30 MPa in an argon atmosphere. The mechanical properties of ZrB2-SiC ceramic composites were improved, adapting to the use requirements of ceramic parts. The precision electromachining technology of complicated structure components was investigated. The processing surface roughness was evaluated.

Al8B4C7 ceramic powder was successfully synthesized via a gas-solid reaction method using aluminum, boron trioxide and activated carbon as the starting materials. The effects of synthesis temperature and the amount of B2O3 addition on synthesis of Al8B4C7 were investigated. The results indicated that the optimized process for preparing the Al8B4C7 was that the mixtures were heated at 1800 °C for 2 h in flowing argon atmosphere. With the heated temperature increasing, the Al8B4C7 content was decreased in the products. And 0.5 molar excess of B2O3 addition promoted the formation of Al8B4C7. The heating samples at 1800 °C had a hexagonal plate-like morphology with ~100 μm in size.

Highly ordered TiO2 nanotubes were successfully prepared via a facile anodization method in ethylene glycol and water mixture electrolyte (99 vol% EG + 5 wt% NH4F). The as-anodized TiO2 nanotubes were crystallized by annealing at 400 °C for 4 hours in argon atmosphere. A series of phosphorus incorporation with different phosphorus content have been prepared by soaking TiO2 nanotubes samples in H3PO4. The photocatalytic activity of TiO2 nanotubes and P-incorporated TiO2 nanotubes were evaluated by the photodegradation of methyl orange. It was found that the photocatalytic activity of P-incorporated TiO2 nanotubes was 34% higher than TiO2 nanotubes.

A new processing concept has been developed to produce nano structured metal matrix composite coatings. Electroless coatings of Ni-P and composite Ni-P-ZnO were developed by co-deposition process on mild steel substrates. Ni-P-ZnO coatings were prepared using conventional route i.e., ZnO particles of ~ 20 μm with average diameter were added to the bath (900C, pH ~9.0) and kept in suspension by stirring. Uniform and grayish bright coatings were observed. The coatings were heat treated at 400°C for 1h in argon atmosphere to attain crystalline nature of coating. The as-synthesized and heat treated Ni-P and composite Ni-P-ZnO coatings were characterized by XRD, FESEM and AFM.

In order to find out the optimum thermodynamic conditions for hot metal dephosphorization and predict phosphorus content after demanganization pretreatment, thermodynamic equilibrium experiments between CaO-FetO-SiO2-MnO-P2O5 slag and silver/solid iron were carried out in an iron crucible at different temperature under pure argon atmosphere in an electric resistant furnace. The results indicate that phosphorus distribution ratios increase with an increase of basicity in the slag at the experiment temperature, and then they decrease with an increase of basicity at 1573K and 1623K. The phosphorus distribution ratios decrease with an increase of FetO content in the slag at 1573K, while they increase with an increase of FetO content in the slag and then decrease with an increase of FetO content in the slag at 1623K. The results indicate that the maximum phosphorus distribution ratio between slag and hot metal is 92.4 when basicity of the slag is 1.7 and FetO content in slag is 49.75 mass% at 1623K, and the correspondent phosphorus content in the carbon saturated iron is 0.019mass%. Dephosphorization is easier under low temperature. The equilibrium quotient of phosphorus obtained in the present work is formulated as a function of slag compositions and temperature using the multiple regression method which is used to predict phosphorus content equilibrium with the demanganization slag and optimum conditions needed for ideal phosphorus contents in demanganization pretreatment.

A new quaternary amorphous alloy powder Ti50Fe22Ni22Sn6are prepared by mechanical alloying. The milling was performed under an argon atmosphere in a high-energy planetary ball mill. After milled 70h, fully amorphous Ti50Fe22Ni22Sn6powders can be obtained, with the condition of the milling speed, 300rpm, and the weighs ratio of ball to powder, 10:1. Crystal structure of the milled powders is investigated by XRD. Thermal analysis show that when the heating rate increasing from 10K/min to 40K/min, the super-cooled liquid region of milled amorphous alloy increased from 93K to 110K.

The pyrolysis characteristics of oil sludge and coal mixed fuel in an argon atmosphere were studied by thermogravimetric analyzer. Factors that affect the pyrolysis process were analyzed. The pyrolysis mechanism equation of the oil sludge and coal fuel was determined. Hereafter, the dynamic properties were provided, namely the activation energy and frequency factor. In this paper, pyrolysis of the mixture occurs in six distinct steps, each accompanied by its unique reactionary mechanics. The activation energy at each step increased with respect to temperature (presenting an initial increase and subsequent decrease). as the rate of temperature increase was amplified, each respective step has its activation energy slightly reduced. Moreover, the mixture shows the influence of non-linear relationships during pyrolysis.

In this research, formation mechanism of a Cu/10 wt.% Cr-10 wt.% Al2O3 nanocomposite via mechanical alloying and subsequent heat treatment has been investigated. It was found that during milling process, Cu (Al) solid solution and Cu9Al4 phase were formed as intermediate products. Further heat treatment carried out under argon atmosphere at 900°C for 8 hours resulted in completion of Cr2O3 reduction by Al. The mechanism of in-situ formation of Al2O3 reinforcement in the copper matrix was also discussed as a two stages process. The SEM and TEM results confirmed the proposed mechanism and showed that the Cr dispersoids surrounded by Al2O3, in the nanometric scale. Also, the Cu matrix with mean crystallite size of 30 nm was stable at high temperature.

Under the protected condition of the purified argon atmosphere, Mo-ZrO2cermets were sintered by Mo powder and ZrO2powder at 1873K for 2 hours. Mircostructure of cermets were observed by means of XRD, optical microscope and SEM anslysis. Electrical properties of sintered samples with different Mo content and temperature were measured using DC four-electrode method. The results showed that metal phase and ceramic phase were independent of each other. With the reduction of Mo content, Mo metal phase as the continuous network structure is dispersedly distributed in the ceramic phase zone. The electrical conductivity of cermets at room temperature increased with decreaseing of the Mo content. The trend that the high-temperature electrical conductivity of cermets changed with the Mo content is the same as the trend that at the room temperature. When the Mo content is greater than 40%, the high-temperature electrical conductivity increased linearly with increasing temperature. The electrical conductivity of 40mol-% Mo-ZrO2reached the peak at 1223K and 1473K.

The wettability between pure liquid titanium and calcia-stabilized zirconia was studied in argon atmosphere. The micrographic observations made on cross section perpendicular to the interface using SEM showed that interfacial reaction occurred. However, the contact angles were larger than 90°within experimental duration.

Impact of heat treatment on hot isostatically pressed (HIP) Ni-base superalloy has been investigated before and after conducting HIP process. HIP was performed by applying a stress of 120 MPa at a temperature of 1200 °C for 2 hours under argon atmosphere followed by furnace cooling to room temperature. Heat treatment cycle was conducted on the samples according to GEB50A563. Microstructural observation demonstrated the deleterious change of  morphology after HIP process which causes to decrease of hardness and creep strength. However, pre heat treatment in compared with cast specimen show slight changes in microstructure but, post heat treatment can revert this change of  morphology completely and also increase the mechanical properties.

Highly pure and dense bulk Ti2AlC was prepared by hot-pressing a mixture of the “312” phase Ti3AlC2 powders, and the element Ti and Al powders. Different ratios of the starting materials and different sintering temperature were attempted in order to obtain a highly pure and dense bulk Ti2AlC sample. Phase analysis and microstructures observing were performed by using by XRD, SEM as well as an X-ray fluorescence spectrometer. The results show that a nearly full dense bulk Ti2AlC sample can be prepared at 1300°C and 30MPa for 30 minutes in argon atmosphere. A dominant mechanism to form the “211” phase Ti2AlC can be attributed to the directly connecting between Al and Ti6C octahedron, which is as an intermediate phase in the Al-rich liquid mediator during the hot pressing.

ZrB2-SiC and ZrB2-SiC-C ultra-high temperature ceramics (UHTCs) were fabricated by pressureless sintering under an argon atmosphere. The mass and linear ablation rates were tested in an oxyacetylene flame with high velocity. The microstructure and phase transformation of the ZrB2-based UHTCs were characterized by scanning electron microscopy along with energy dispersive spectrometry. Results show that the UHTCs have excellent properties of ablation resistance at ultra-high temperature. The values of mass and linear ablation rates were lower in the ZrB2-SiC UHTCs than those measured for ZrB2-SiC-C. The effect of C addition on the ablation resistant was not obvious but it influenced the microstructure of the ZrB2-SiC UHTCs. And the ablation resistant mechanisms of ZrB2-based UHTCs were discussed according to microstructure analysis.

The high-powered brazing diamond saw was developed to cut vehicle tyre efficiently. The Ti-coated diamond and the uncoated diamond were brazed with NiCr alloy by high-frequency induction under argon atmosphere at 1020°C within 10 seconds. The interfacial microstructures between brazed diamond and the filler alloy were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersion spectrometer (EDS). It is surprisedly found that Cr-carbides forms compactly and normally on the surface of Ti-coated diamond brazed, whereas Cr-carbide forms loosely and tangentially on the surface of uncoated diamond brazed. The abrade experiment results for the brazed diamonds show that the bond strength between the Cr-carbide and uncoated diamond brazed is lower than the normally formed Cr-carbide and the diamond. Furthermore, the cause that Ti changes the morphology of Cr-carbides on the surface of Ti-coated diamond brazed is discussed by the further tests that are specially designed.

In the present work, biomorphic TiC/C ceramic with a woodlike structure was synthesized from wood template. The TiC coatings were formed on the surface of C-wood-template in a reaction medium consisting of Ti powder in a mixture of molten LiCl-KCl salts under an argon atmosphere. The structure and biomorph of the TiC/C ceramic were characterized by XRD, TG-DSC, SEM and EDX analyses. The results indicated that Ti powder had reacted with carbon in the cellular wall to form TiC coatings. The resulting biomorphic TiC/C ceramic retained well the structure of the original biomorph of the wood.

Solid-state direct diffusion bonding between commercially pure nickel and tungsten carbide (with 6%Cobalt) has been carried out in the temperature of 980°C and 1100°C using different holding times in argon atmosphere. Samples were successfully joined without defects or cracks on the joining interface with the exception of the one joined at 980°C for 5 min. The results showed that joining occurred by the formation of a reaction zone. Scanning electron micrographs show that different intermediate layers are formed in the reaction zone, and the width of these layers increases with an increase in bonding temperature and time. Electron probe microanalysis revealed that at any particular bonding temperature, cobalt travel into the nickel side, whereas nickel travel comparatively larger distances in the tungsten carbide side.

In this study, weldability of bronze parts produced by powder metallurgy has been investigated by using TIG welding technique. Bronze powders were pressed into 55x44x5 mm size specimens under pressure of 350 MPa. Then these specimens were sintered at 650, 750 and 870 °C for 45 minute under argon atmosphere. Finally, the parts were welded by TIG welding method. Hardness values of the welded joints were measured and microstructural features were investigated.

The paper’s aim is to present the processing of a new master alloy similar to STROBLOY. This alloy represents a combination of two master alloys, already known in aluminum industry (AlTiB and AlSr). The benefits of this new alloy are the cut of Ti, B and Sr consumption, as well as a grain refining/modification ecological technology for Al-Si and Al-Mg-Si alloys. So, this alloy was obtained from binary AlB8, AlSr10 and AlTi10 master alloys melted in an electric resistance furnace and argon atmosphere. Samples were cast in an iron mould. As STROBLOY, this new quaternary alloy contains fast dissolving SrAl4 particles important in modification stage, and nucleating particles such as TiB2 and (Al, Ti)B2 essential for grain refining of aluminum alloys.

Ceramic coatings with the main crystalline of TiO2 were prepared on Ti-6Al-4V alloy by pulsed bi-polar Micro-arc Oxidation (MAO) in Na2SiO3 solution. The coated samples were calcined in argon under 1000oC. The phase composition, morphology and element content of the ceramic coatings were investigated by XRD, SEM and EDS. The results showed that the main components of the coatings are TiO2 and amorphous substances, after oxidation in argon, SiO2 was crystalized in coating. The content of elements in the coatings both changed a little.