Advanced Materials Research Vols. 154-155

Abstract: Electrical explosion of wire has a prosperous future in fine powder producing. In the process of electrical explosion of segmented metal wire (EESW),energy deposited in the wire was influenced by process variables such as the initial charging voltage of the capacitors, the length and the diameter of the segmented wire,and the electrode spacing. For understanding their relation completely, a series of experiments of electrical explosion was carried out with variations of the initial charging voltage and the segmented wire lengths and diameter. Results show that, energy deposition efficiency was weakly dependent on the wire length , whereas it has a strong dependence on the wire diameter, the initial charging voltage of the capacitors have an important influence on the energy deposition.

Abstract: In this work, the feasibility of using planetary ball milling for coating bearing balls with a self-lubricating film was investigated. Bearing balls with appropriate amount of MoS2 powder were put into vacuumed stainless steel vials and ball milled. With proceeding of ball milling, thickness of the self-lubricating film increased at first and then decreased. X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) results revealed that the surface of the self-lubricating film was MoS2 and the inner region was a mixture of iron molybdenum alloys (Fe3Mo, FexMoy), MoS2 and FeS. Friction coefficient between the self-lubricating film and bear steel was 0.06~0.1.

Abstract: Used periodic table of elementsⅤA first group elements X, Ni instead of Sn-Ag-Cu series Ag to prepare a new type of lead-free solder SnX4.5Cu1.5Ni.Studied this solder and the welded joint microstructure under the low temperature environment performance compared with SnAg3.0Cu0.5 and Sn63Pb37. The results show that: the electrical conductivity of SnX4.5Cu1.5Ni under low and normal temperature was greater than that of Sn63Pb37.The tensile and shear strength of them decreased when the temperate decreased, however the strength then improved when the temperature dropped to -20 . In addition, SnX4.5Cu1.5Ni was ductile fracture, Sn63Pb37 was brittle fracture and SnAg3.0Cu0.5 was mixed fracture at low temperature.

Abstract: The dynamic evolution of grain growth in the process of aluminum casting and the impact of different casting conditions on the grain growth were simulated by using the Cellular Automation(CA) method in this paper. The simplified binary alloy was used to simulate the growth of the grain in the undercooled melt, Finite Difference Method (FDM) combined with relative motion was used, and dynamic evolution of microstructures in the process of aluminum twin-roll casting was achieved. Visual Fortran programming language was adopted to calculate and realize the image post-processing. based on the growth of the grain in the undercooled melt, the impact of the undercooling triggered by cooling and the casting speed on aluminum strip in the casting process was simulated. The results indicate that, in the condition of a certain nucleation rate, as the cooling intensity increases, bigger the grain is, which provides a basis for optimizing the twin-roll casting process parameters.

Abstract: In this paper, polymerization of acrylic acid (AA) monomer on PVDF microfiltration (MF) membrane by dip-coating to immobilize Pd/Fe nanoparticles (NPs) was prepared. The modified PVDF membrane-immobilized Pd/Fe NPs was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), the result showed that the distribution of Pd/Fe nanoparticles was uniform. The modified PVDF membrane-immobilized Pd/Fe NPs were used to dechlorinate monochloroacetic acid (MCAA) exhibited high reactivity.

Abstract: Large-span space steel structure, rotary hearth furnace lower ring, has dynamic stress at work caused by shock or vibration leading to the destruction of steel, so in the design of rotary hearth furnace lower ring, dynamic design is an essential part [1, 2]. Finite element analysis software ANSYS is used to build its finite element model. Modal analysis is carried on, and experimental data is compared with the calculation result, which effectively estimates the vibration characteristics and structural optimization design of the structure, and provides strong technical support for its design and manufacture[3, 4].

Abstract: The causes of machining errors are very complicated and apt to mutual influence in aspheric grinding, so it is difficult to improve machining accuracy by control one cause. To compensate the machining error of large aspheric grinding, an error-compensation technique using on-machine profile measurement system in three axes grinding machine are presented. To verify the effectiveness of the compensation machining and the reliability of the measurement system, experiments on high-precision grinding machine were performed. Moreover, the compensation machining with the on-machine measurement substantially decreases the machining errors and improve machining accuracy by more than 45%, compared with the non-compensation machining.

Abstract: The roller gear cam surface is often machined by the unequal diameter manufacture method, which means the tool diameter is smaller than that of the roller and the tool position compensation method is most used. For tool position of roller gear cam, it is important to confirm the compensation vector for the tool position compensation method, including compensation value and direction. In the paper, a new self-adaptive tool position optimization method is proposed, which make minimizing the normal machining error as the object function and make two compensation factors as the optimization variables. This algorithm can find out the best compensation direction and value by the tool position optimization for any cam rotation angle and make the tool position self-adaptive and flexible compensation according to the machining error. A numerical calculation example shows that the optimization algorithm can feasibly reduce the machining error. At last a conclusion has been drawn that the radius difference between the tool and the roller is the best compensation value and the best compensation direction is not fixed.

Abstract: The evolution of interface morphology for a single-phase Nickel-Copper binary alloy in directional solidification is studied by using a phase-field model cooperated solute concentration gradient corrections. The effect of pulling velocity V and strength of the crystalline anisotropy γ on interface morphology and the solute segregation is formulated. The results indicate that, the transition from plane to cells/fine cellular structures, then to planar structures(plane-cell-plane) will happen with the increment of V, and the level of solute trapping becomes stronger. When the crystal grows with cellular structures, γ crucially influences the interface pattern formation at the lower growth velocity, but the solute partition ratio is not significantly affected by the anisotropy strength. Then, the operating behavior for planar growth is hardly any affected by the crystalline anisotropy.

Abstract: NiCrBSi+Ti+C and NiCrBSi+TiC composite coatings were fabricated on H13 steel substrate by laser claddings to improve its wear resistance. The macroscopic qualities of the coatings were analyzed and the process parameters and the clad materials were optimized. The microstructure of the coatings was characterized by SEM. The microhardness of the coatings was examined using HXD-1000 microhardness tester. The wear properties were examined using M-200 wear test machine. The results show that the clad materials and the process parameters are the important factors to influence the quality of laser cladding. Ni+Ti+C organization is smaller, particle strengthening and grain refinement is more significant. The hardness of the clad coating of NiCrBSi+Ti+C coatings reaches HV900, which is improved by almost three times compared with the substrate H13 steel.