Materials Science Forum Vols. 471-472

Abstract: The direct laser metal sintering experiments were carried out with nickel alloy powder material system. The melting–solidification approach was discussed. Microstructure and components of DLMS-process sample were analyzed. The incomplete liquid phase sintering is the main mechanism of the melting-solidification approach. In powder material system, the additive copper improves the wettability of melting material, and minimizes the balling phenomenon. The equiaxial dendrite and the dendrite are the primary crystal morphologies. The compositions of materials are distributed uniformly.

Abstract: In this paper, the technique of high energy and short pulse duration laser impact is adopted. The substructural transformation characteristics and mechanisms of the austenitic stainless steel, subjected to strain-rate of 106s-1 order and stress of 2.70GPa, are investigated. SEM observations, there exists regular arrangement of chapped and equiaxed subgrain regions within the original grains. The size of the subgrain ranges from 0.1 to 0.5um; Meanwhile, the compacted deformation twin bundles with about 1um width each twin have been examined in the regions treated. It indicates that the equiaxed subgrains, close to nanometer scale, had evolved in the surface of austenitic stainless steel, and they belong to dynamic rotational recrystallization; Although, twinning deformation is not a frequent phenomenon in terms of austenitic stainless steel at room temperature, it will play a significant role when austenitic stainless steels are submitted to high strain rate and stress. Additionally, X-ray diffraction reveals that the crystal lattice constant is up 1.12% compared to the normal one and no deformation-induced α-martensite and amorphous phase are spotted within the processed regions.

Abstract: Cathodic Arc Physical Vapor deposition (CAPVD) uses a high current, low and negative voltage arc to vaporize a cathodic electrode (cathodic arc) and deposit the vaporized material on a substrate. The vaporized material is ionized in a vacuum chamber and the substrates are usually biased so as to accelerate the ions to the substrate surface. CAPVD provides a very dense film with excellent adhesion to the substrates. Therefore, this technique is mainly used to deposit on cutting tools such as end mills, drills, inserts, plastics and metal molds and high wear resistance tribology components. However, this coating technique will produce unwanted micro particles (droplets) [1] which usually are the target materials that cannot be reacted in coating process. These particles will affect the coating roughness and the surface morphology. To optimize this condition, Taguchi method is introduced to obtain the best experimental parameter settings. In this study, Atomic Force Microscope (AFM) is used to analyze the roughness of the coating for the following factors: bias voltage, arc current, nitrogen pressure and coating thickness.

Abstract: More powerful process design methods and tools of sheet metal stamping are needed to help engineers design better products, to reduce lead times and costs, and to increase product performance and accuracy. A novel model for representation of object-oriented case information constitution relationship is presented, ‘Class-Property’ structure is proposed in order to refine the case representation, multi-types, properties are adopt to describe more detailed information, three hierarchies of index strategy are used to realize case extraction. Furthermore, experts’ knowledge and experience on previous design cases and forming problems are collected, which can provide designers useful practical experience and data to aid design procedure and to solve the potential problems of sheet metal stamping. In order to illustrate these applications, database technology is used to realize a prototype system of auto body panels, which can be used to integrate process design information and manufacture resources.

Abstract: In order to improve the application of neutron scattering technique, a new neutron optical device, which optical system consists of an array of several ten neutron Fresnel lenses, is designed by the researcher engaging in the study of neutron optics. Neutron Fresnel lenses for this new device have the same symmetric concave form. Its center is a spherical surface and the other surfaces are conic section. MgF2 single crystal glass is selected as the material for making neutron Fresnel lens because of its high transparence. Considering the form complicity and the brittle properties of MgF2 material, the fabrication of neutron Fresnel lens is of very difficulty. Form ELID (electrolytic in-process dressing) grinding was used for grinding the neutron Fresnel lens in this first study. The optima of grinding conditions for #325, #1200 and #4000 cobalt bonding diamond abrasive wheels are obtained through a series of tests. The MgF2 material is removed at the ductile mode by using #4000 abrasive wheel. Thus, the neutron Fresnel lens fabricated has low roughness and high transparence. The transmission of an array of 50 pieces of neutron Fresnel lens is 92.5 percents to neutron beam with wavelength 5Å and 79.3 percents to 16Å.