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In this research, carbon sources (Resin Phenolic, Carbon Black and Graphite) and Boron Carbide (B4C) were used to improve the mechanical properties of Silicon Carbide (SiC) composite. For this purpose, carbon sources of 0.5, 0.75, 1, 1.5, 2, 2.5, 3, and 5 wt% as well as 0.5 wt% B4C were added to SiC powder, respectively. The sample containing SiC—2.5 wt% Resin Phenolic—0.5 wt% B4C had the best properties with relative density, hardness, and fracture toughness values of 98.5%, 2820 GPa, and 3.9 MPa.√m, respectively. Examination of SEM images showed that by increasing carbon from 0.5 to 2.5 wt%, the fracture changes from intergranular to transgranular. [ABSTRACT FROM AUTHOR]

Intermetallic compounds because of their high melting point temperature, good mechanical properties, and high corrosion resistance are attractive. The Zr2Cu intermetallic compound can be produced by a mechanical alloying method. In this study, alloying was carried out by using the pure copper and zirconium powders under argon atmosphere at different time durations from 30 to 120 minutes. Milling speed was chosen as 220, 250, and 280 rpm. Mechanical alloying was done with five different balls to powder ratios (BPR) of 1:10, 1:15, 1:20, 1:25, 1:50. Prepared powders were studied by X-Ray Diffraction (XRD). XRD results showed that with increasing milling time and ball to powder ratio, the amount of amorphous phase increases, however, particle size reduces. By increasing the ball to powder ratio, speed and time of milling crystallite size decreases, but lattice strain increases. [ABSTRACT FROM AUTHOR]

In the present study, A1-B4C nanocomposite was produced using the methods of casting vortex and semi-solid casting. Boron carbide particles with an average diameter of 65 nm with the amount of 3 wt%, was added to the melted alloy of A356. In the method of Casting Vortex, boron carbide particles were added to the melted aluminum at 850 C° in 15 min and then casting was performed. In the semi-solid Casting method, temperature first rose to 700 C° when particles were mixing and then temperature was reduced to 608 C° within 15 min and then casting was done. Results show that tensile strength of the segments produced by semi-solid Casting method is 201 MPa which shows a 12% increase in strength compared to the segments produced by Casting Vortex with tensile strength of 178 MPA. [ABSTRACT FROM AUTHOR]

Abstract: In this study the W-ZrC composites fabricated by in situ reaction sintering of two precursors were compared, 1-The conventional WC and ZrO2 which are ball milled with established molar ratio of 3–1 for 12hours, gelcasted to form a green body and then undergo a pressure less sintering cycle, 2-A new and innovative way in which for the first time ZrSiO4 was used instead of ZrO2, and by testing different molar ratio between WC and ZrSiO4 it was understood that the optimum ratio is 3–1 once again. Furthermore the starting ZrO2 and ZrSiO4 powder were selected in nano size and it was understood that by using nano powders the amount of unreacted and unwanted phase reduce, the reaction progress and the mechanical proprieties improve. Although the reaction sintered WC/ZrO2 possess better properties, regarding the cost considerations, reaction sintering of WC/ZrSiO4 is a much cheaper process. [Copyright &y& Elsevier]

Boron carbide (B4C) has wide application in manufacturing of abrasives and cutting tools, due to its unique features such as high hardness, good wear resistance, low specific weight and chemical stability. An additive reinforcing phase and sintering aids are used to improve its sinterability. In the present paper, a B4C composite with 10vol.% of titanium diboride nanoparticles (TiB2) and a 0, 1.5 and 2.5vol.% iron or nickel metallic additive, respectively, was mixed in an isopropanol environment containing tungsten carbide pellets. After drying, the obtained mixture was formed by cold pressing. The obtained parts were sintered at 2400°C. The effect of adding metallic sintering aids on the mechanical properties and microstructure of the composite was investigated and fracture toughness values were evaluated by indentation test method. Addition of Fe and Ni improved values for density, hardness, Young's modulus and fracture toughness, with Ni addition increasing the values considerably. Scanning electron microscope (SEM) images of the microstructure of the specimens showed the arrangement posture of the additives and confirmed the results obtained. Additionally, the FeB and Ni3B blades formation were observed from the images. [ABSTRACT FROM AUTHOR]

In the present work, rheological behavior of tungsten carbide (WC) slurries was evaluated to utilize it in gel-casting process, and effects of dispersant quantity and solids content on the viscosity of WC slurries were examined. It was found that tri-ammonium citrate to WC powder ratio of 0.25 was a preferable dispersant in such a non-toxic system. Maximum allowable WC powder was 25vol.% in the slurry. The slurry with 25vol.% WC powder and gelation additives was prepared, cast and dried at room temperature, then it was pre-sintered at 1450°C for 4h. Scanning electron microscope (SEM) micrograph of the pre-sintered WC foam showed a uniform porous microstructure. It had enough strength to be infiltrated with Zr2Cu molten. A reactive melt infiltration occurred during the practice, resulting in the formation of about 58vol.%W and 42vol.% ZrC in the final microstructure. [ABSTRACT FROM AUTHOR]