Papers by Keyword: TiB₂

Abstract: AlMgB₁₄ is a very hard and brittle material which need be modified for utilizing as cutting tool materials. In present study, TiB₂ and Ni₃Al were used to strengthen and toughen AlMgB₁₄ material. The microstructure of the AlMgB₁₄-TiB₂-Ni₃Al composites was analysized by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and an X-ray diffractometer (XRD). The hardness and fracture toughness of the AlMgB₁₄-TiB₂Ni₃Al composites were also examined. The results showed that the major phases in AlMgB₁₄-Ni₃Al composites were TiB₂, AlMgB₁₄, MgAl₂O₄ , Ni₃Al and NiAl. With the increasing of the amount of Ni₃Al, more intergranular fractured features can be found in the fractured surface of the composites, the hardness and fracture toughness of the composites were both decreased comparing to the synthesised AlMgB₁₄. The AlMgB₁₄-TiB₂-4wt.% Ni₃Al composite has a hardness of 28.1 Gpa and a fracture toughness of 3.14 MPa·m^1/2.

Abstract: There are relevant reports on preparing TiB₂ particle reinforced metal matrix composite (MMC) anti-wearing coating by plasma spraying and HVOF spraying methods successfully. The research uses electric arc spraying with low cost and convenient operation to prepare four TiB₂ particle reinforced composite coatings with high bonding strength and uniform microstructure. It makes comparative study on elevated temperature erosion actions of coating and 45CT of electric arc spraying. The results indicate the coating has excellent erosion wearing resistance. TiB₂ particles in M-TiB₂ coating have small size, have good unity with metallic matrix, and are distributed on metallic matrix with high hardness relatively uniformly, and porosity of coating is low. Such MMC coating microstructure feature avoids micro-cutting of coating effectively, and reduces plastic deformation and material transfer of wearing surface. The coating has excellent erosion resistance.

Abstract: Al-Ti-B master alloy is the most widely used grain refiner in the aluminum fabrication industry, while it’s refinement mechanism is not clearly understand yet. The TiB₂ in Al-Ti-B master alloy is one of important phase to grain refining, which intimately related to the generation of initial nucleus, the “fading” phenomenon of refining effect declines with the increase of holding or standing time in grain refining process. Besides, TiB₂ is analyzed in several studies about the “poisoning” phenomenon, a large extent weaken of refining effect when Zr, Cr, Mn etc. exists. In this article, the impact of TiB₂ to the refining effect of Al-Ti-B master alloy is discussed aiming at the roles and phenomenon mentions above.

Abstract: Based on the experimental and calculation results between the reinforcing particles content and thermal physical parameters, low pressure die casting of wheels was taken as an example to study the casting property of the 7075 alloy and TiB₂/7075 composites. The influences of die temperature, pouring pressure, pouring temperature and TiB₂ content on the filling of 7075 alloy and TiB₂/7075 composites wheels are studied by numerical simulation. Shrinkage porosity appears both in the spoke and rim of the wheel. The shrinkage porosity of the 7075 alloy decreases from 2.089% to 1.622% with mold temperature increasing from 100°C to 400°C. The shrinkage porosity of wheel decreases from 1.630% to 1.598% and 1.583% in the composite with 3 and 6wt.% TiB₂ particles. Besides, shrinkage porosities decrease with increasing pouring temperature.

Abstract: Using TiO₂B₂O₃ powders as oxidizer,AlMg powders as reducer,the TiB₂ multiphase ceramic are preparated with SHS, and analysed with SEM and XRD.The effect of HCl, H₃PO₄ to pickling of TiB₂-based multiphase ceramics is explored by SEM and XRD analysis. Research suggests that: the main ingredients of TiB₂-based multiphase ceramics is TiB₂, MgO and MgAl₂O₄ three phases, few of reaction residual objects and impurities also exists; the multiphase ceramics is forming by many of hexagonal crystal type products and small particles reunion, hexagonal crystal type product is TiB₂, small particles may be MgO, MgAl₂O₄ and other impurities product; MgO can be effectively washed by HCl and H₃PO₄ , but TiB₂ and MgAl₂O₄ invalid. At room temperature, 30% HCl pickling has the best effect, the concentration of TiB₂(ω) is up to 59.3%; the higher of the concentration, the better of acid-effect; In the pickling process, as the temperature rises, the concentration of TiB₂ grows, but the temperature should not be too high. When temperature reach 75 °C, HCl volatilizes too quickly and inefficiently. At room temperature, 20% H₃PO₄ has the best pickling effect, the concentration of TiB₂(ω) is up to 52.6%, but the best pickling effect is not well with concentration increasing; as the temperature increasing, purity of TiB₂ is also increased; At 70°C, the concentration of TiB₂(ω) after H₃PO₄ pickling is up to 61.9%, refine effect is good.

Abstract: On the basis of magnesiothermy, with Mg powder, TiO₂ powder and B₂O₃ powder as mixed reactants, relatively pure TiB₂ powder was prepared by self-propagating high temperature synthesis (SHS) after leached in diluted hydrochloric acid with the suitable concentration. The product after leached was examined by XRD for qualitative and quantitative analysis, SEM for morphology analysis and infrared spectroscopy for transmittance analysis. It was found that diluted hydrochloric acid could decrease most of the impurities, and the proportion of TiB₂ phase in the product is more than 99%, which was hexagonal shape crystal with the grain size of 200-300 nm. Compare with the infrared spectrogram of the middle infrared spectral region of the product of before and after acid pickling, it was found that the transmittance of TiB₂ is extremely low in the range of 2000-4000 cm^-1, which can be excellent infrared absorption material in the corresponding wave band.

Abstract: The effects of in-situ TiB₂ particle fabricated from Al-Ti-B system via the self-propagating high-temperature synthesis (SHS) reaction technology on microstructure and mechanical properties of Mg-Sn-Zn-Al alloy were investigated. The results indicate that the size of the Mg₂Sn and α-Mg+Mg₃₂(Al,Zn)₄₉ phase becomes coarser with the increasing content of Al-Ti-B preform, meanwhile the amount of eutectic α-Mg+Mg₃₂(Al,Zn)₄₉ phase increases too. The addition of Al-Ti-B is favorable toward promoting the strength of composites, but deteriorates elongation. The resulting as-extruded composite material with 4 wt.% Al-Ti-B preform exhibits good overall mechanical properties with an ultimate tensile strength of 291 MPa and an elongation over 2 %.

Abstract: TiB₂ and Gd₂O₃ were used as codeposited particles for the first time in preparing Ni-TiB₂-Gd₂O₃ composite coatings to improve its performance. Ni-TiB₂-Gd₂O₃ composite coatings were prepared by electrodeposition method from a nickel cetyltrimethylammonium bromide and hexadecylpyridinium bromide solution containing TiB₂ and Gd₂O₃ particles. The content of codeposited TiB₂ and Gd₂O₃ in the composite coatings was controlled by the addition of different TiB₂ and Gd₂O₃ particles concentrations in the solution, respectively. The effects of TiB₂ and Gd₂O₃ content on microhardness, wear weight loss, and friction coefficient of composite coatings were investigated, respectively. Ni-TiB₂-Gd₂O₃ composite coatings shows higher microhardness and lower wear weight loss, friction coefficient than those of the pure Ni coating and Ni-TiB₂ composite coatings. The wear weight loss of Ni-TiB₂-Gd₂O₃ composite coatings is lower 9.13 and 1.59 times than that of the pure Ni coating and Ni-TiB₂ composite coatings, respectively. The friction coefficients of pure Ni coating, Ni-TiB₂ and Ni-TiB₂-Gd₂O₃ composite coatings are 0.723, 0.815 and 0.43, respectively. Ni-TiB₂-Gd₂O₃ composite coatings shows the least friction coefficient among the three coatings. Gd₂O₃ particles in composite coatings serves as solid lubricant between contact surfaces, decreases the friction coefficient, abates the wear and increases the corrosion resistance of the composite coatings. The loading-bearing capacity and the wear-reducing effect of the Gd₂O₃ particles in the composite coatings are closely related to the content of Gd₂O₃ particles in the composite coatings.

Abstract: Ni-TiB2-Gd2O3 composite coatings were prepared by electrodeposition method from a nickel cetyltrimethylammonium bromide and hexadecylpyridinium bromide solution containing TiB2 and Gd2O3 particles. The composite coatings were characterized with X-ray diffraction (XRD), atomic emission spectrometer (ICP-AES), scanning electron microcopy (SEM) and energy- dispersive analyses of X-ray (EDAX), respectively. That the codesposition of TiB2 and Gd2O3 into the coatings were demonstrated by XRD, EDAX, ICP-AES and SEM. TiB2 and Gd2O3 entered the lattice of Ni. The incorporation of TiB2 and Gd2O3 particles in the matrix can largely reduce the wear of the nickel composite coatings.

Abstract: Micro-nanoTiB₂ ceramic was prepared through increasing the molar ratio of Mg and leaching with suitable acid by the combustion synthesis reaction of Mg, TiO₂ and B₂O₃, which could get higher temperature and purer product. The Samples were investigated by XRD and SEM, and the results showed the diameter of the TiB₂ was 200 nm ~ 300 nm and the shape of the TiB₂ was irregular hexagonal crystal. The diameter of the TiB₂ was decreased with the increase of Mg powder. The formation mechanism of TiB₂ has been studied.