Papers by Keyword: Graphite Particle

Abstract: Self-lubrication CBN abrasive composite blocks and corresponding grinding wheels were made through the sintering process of CBN grains, graphite particles and Cu-Sn-Ti alloy at 920° for 30 min. The mechanical strength of the composite blocks was measured by means of the three-point bending experiments. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were employed to characterize the fracture morphology and the interfacial microstructure of the composite blocks. Dressing experiments were carried out and the graphite film on the CBN grain surface was observed. The results obtained show that the bending strength of the composite blocks with 5 wt.% graphite particles reached 116 MPa, which met the mechanical requirements of the working layer of the grinding wheels. Chemical joining has taken place at the interface of CBN/Cu-Sn-Ti and graphite/Cu-Sn-Ti during the sintering process. Graphite film has been formed and spread to the grain surface after dressing.

Abstract: The graphite and alumina particles reinforced Al matrix composites with graphite up to 5 vol% was prepared by Reciprocating Extrusion (RE). Damping behavior of the composites was measured by dynamic mechanical thermal analyzer. The composites showed more excellent damping Q-1 than pure Al manufactured by RE, and the ambient value was 9.9×10-3 at 5 Hz when the strain amplitude was 8×10-8. The damping behavior of the composites showed slight variation with frequency. The damping capacity increased with increasing of the strain amplitude when the amplitude less than 1.5×10-6, and then became a constant and independent of strain amplitude. The high damping capacity was attributed to micro-sliding interface damping and the dislocation damping.

Abstract: This paper presented the composite coatings of nickel with graphite particle on the aluminum substrate using a nickel sulfamate bath. Effects of graphite particle concentration on the surface morphologies of the composite coatings were investigated. The inclusion of graphite particle into metal deposits was dependent on many process parameters, including particle concentration, current density, pH and temperature. Results of SEM and XRD demonstrated that graphite particle had successfully deposited on that nickel matrix; besides, the surface morphology of coatings obtained from sulfamate bath containing 2g/L graphite particle dispersed more uniformly than the ones with higher concentration.

Abstract: Copper-40mass%zinc (Cu-40Zn) brass alloy powder containing 1.0 mass% Cr was prepared by the water atomization. Graphite particles, having a mean particle size of 5 μm, were added to the as-atomized powders by the ball milling equipment for 4h under 120 rpm. Spark plasma sintering process was used to consolidate the above elemental mixed powders (sintered material). Sintered materials were heat-treated for the precipitation of much Cr (HT material). The machinability of Cu-40Zn brass alloys was evaluated by a drilling test using a drill tool under dry conditions. The matrix hardness of sintered material was higher than that of HT material. On the other hand, the machinability of sintering material was higher than that of HT material. There is no trade-off relationship between the matrix hardness and machinability of the brass alloys. SEM-EDS observation indicated that Cr content dissolved in the brass matrix of sintered material and HT one was 0.42 mass% and 0.19 mass%, respectively. As the reason why machinability of HT material lowered, the precipitation of the hard Cr particle or generation of Cr-C compound caused to inhibit the machinability.

Abstract: Mg alloy is the lightest material of structural materials and is noticed for lightweight automotive parts because of excellent castability and damping capacity compared with Al alloy. But Mg alloy has poor corrosion resistance and high temperature creep properties. In this study, Mg matrix composites were fabricated by squeeze casting method to improve high temperature creep properties and damping capacity. The creep properties and damping capacity of hybrid Mg composites reinforced with Alborex(Aluminum borate whisker: 9(Al2O3)•2(B2O3)), graphite particle, and carbon fiber were improved in comparison with Mg alloy. Hybrid Mg composites reinforced with carbon fiber and Alborex were better than those reinforced with graphite particle and Alborex in mechanical properties, creep characteristics, and damping capacity, etc.

Abstract: Mg alloys have potential to use automotive parts because of their weight and castability. High temperature strength and damping capacity is important to the automotive power train parts. Mg alloy has lower creep and thermal fatique strength but has better damping capacity than Al alloy. It is known that short fiber reinforced Mg metal matrix composites(MMC) exhibits superior high temperature strength and graphite reinforced Mg MMC shows excellent damping capacity. Therefore, in this study, the effect of graphite particles(15-25%) and alborex (9Al₂O₃ּ2B₂O₃) whiskers(5-15%) on the damping behavior and mechanical properties of Mg MMC was studied. Graphite particles and alborex whiskers were chosen to increase damping capacity and high temperature strength, respectively. The Mg MMC was fabricated by squeeze casting and the total quantity of reinforcements(graphite + alborex) was maintained to 30 volume percent. The damping capacity of the metal matrix composites was increased and the flexural strength and hardness were decreased with increasing the volume fraction of graphite particles, that is, reducing the volume fraction of alborex whiskers.