Advanced Materials Research Vols. 560-561

Abstract: The bending performance of lead frame materials is a very important in improving the quality of lead frame alloys and meeting the needs of high performance integrated circuit. The sringback amount of curvature variation of CuFeP , CuCrZrMg , CuNiSi and CuCrSnZn alloy are researched by numerical simulation. Bending model is built by 3D modeling software, and the necessary post-processing is carried out. The bending springback amount △K of the four kinds of copper alloy materials are calculated out. The results show that the sringback amount of curvature variation of four copper alloys at the same condition from large to small in turn is CuCrZrMg, CuNiSi, CuFeP, CuCrSnZn. Smaller the minimum relatively bending radius of copper alloy used in lead frame, less the springback amount and better the forming performance.

Abstract: Abstract. Micron-sized WC-metal (WC-0.6%C-21%Cr-6%Ni) powder was coated onto the substrate of magnetic bearing shaft material Inconel718 (substrate or In718) using JK3500 HVOF thermal sprayer for the improvement of the surface properties of the substrate. The optimal coating process for the highest surface hardness was obtained using the Taguchi experimental program. The coating was laser heat-treated (LH) by CO2(g) laser for further improvement of the properties. During the thermal spraying, a small portion of metal carbides of powder decomposed to W2C, metals and free carbon. The free carbon reacted with excessively sprayed oxygen, and formed carbon oxide gases, forming porous coating. By laser-heating, porosity decreased and the porous strips at the interface of coating and substrate (coat/sub) compacted. At the interface, the precipitated graphite concentration decreased and the metal elements diffused from both the coating and substrate increased, enhancing the functions as buffer zone and increasing adhesion of coating. The surface hardness of substrate increased by coating and further increased by laser-heating from 410±30 Hv to 983±101 Hv and 1425±94 Hv respectively. Porosity of coating decreased by laser-heating from 2.6±0.4% to 0.35±0.06%, and coating thickness shrank from 280㎛ to 200㎛. Friction coefficients of substrate decreased from 0.52±0.02 to 0.36±0.04 by coating, because the free carbon formed by decomposition of WC to W2C functioned as a solid lubricant. By increasing sliding surface temperature from 25°C to 450°C, the friction coefficients of substrate and coating were decreased from 0.52±0.02 to 0.31±0.02 and from 0.36±0.04 to 0.23±0.04 respectively, because of easy formation of free carbon and metal oxides which functioned as solid lubricants. Wear depth of surface was decreased by coating and by LH coating from 55µm to 32 µm and to 12 µm respectively. HVOF coating of WC-metal powder on In718 surface and laser heat-treatment of the coating are highly recommended for the improvement of the properties of magnetic bearing shaft.

Abstract: The self-made device to test the shrinkage ratio and temperature of cast ingot is used to measure the shrinkage mass of Fe-0.1%C, Fe-0.15%C, Fe-0.33%C cast ingot with the dimension of 200×80×100mm. The results show that the total shrinkage mass of cast ingot is increased with the increase of carbon content. In the carbon content range of the experiment, the rate of shrinkage and expansion of Fe-0.15%C steel during, before and after eutectoid reaction is all the quickest. The solid-state shrinkage rate of Fe-0.15%C steel before eutectoid reaction is 288 μm•s-1. The shrinkage mass and rate of cast ingot after eutectoid reaction are 0.051 mm and 127 μm•s-1, respectively. The expansion mass and rate of cast ingot during eutectoid reaction are 0.016 mm and 53.3 μm•s-1, respectively.

Abstract: The kinetics and products of oxidation of binary Co-5Si alloys in 1 atm of pure O2 at 700 and 800 oC were investigated. Co-5Si alloys followed a parabolic behavior to a good approximation (n=2). The parabolic rate constants as functions of temperature were 2.789×10-11, 2.240×10-10 g2cm-4s-1 at 700 and 800 oC, respectively. The scales formed on Co-5Si alloys were double-layered, with formation of an outer layer of columnar CoO and an inner region containing a mixture of SiO2 and CoO, coupled to the internal oxidation region of Si.

Abstract: The kinetics and products of oxidation of ternary Co-10Cr-5Al alloys in 1 atm of pure O2 at 700 and 800 oC were investigated. Oxidation of the alloys approximately obeyed the parabolic rate law. The scale formed at 700 oC was composed of an outer CoO layer and an inner complex layer rich in Al2O3 and Cr2O3 which were intermingled with spinel Co(Cr, Al)2O4. There was no internal oxidation zone beneath the scale. However, as shown by Fig. 3. b, internal oxidation zone of Al or even Cr was obviously present beneath the scale formed at 800 oC, though the scale was of a similar microstructure with that at 700 oC.

Abstract: The characteristics of hot compression deformation of Ti-3.0Al-3.7Cr-2.0Fe titanium alloy have been studied by Gleeble−1500D thermal simulated test machine in the strain rates range 0.01～10s−1 and temperature range 800～950°C. The true stress-true strain curves show that the peak flow stress decrease with increase temperature and decrease strain rate. At the temperature range in the article, there is a distinct peak in the flow stress in the early stage deformation followed by a stable state at high strains. The variation of flow stress with temperature and strain rate follows the standard kinetic rate equation and the apparent activation energy is estimated to be about 214.22KJ•mol-1. The constitutive relationship of Ti-3.0Al-3.7Cr-2.0Fe alloy is obtained on the base of Arrhenius equation at the experimental conditions.

Abstract: The porous Cu specimens were prepared using infiltration process. Its damping behavior was investigated using multifunction internal friction apparatus over the temperature range from 40°C to 500°C.The size of macroscopic pore is in the order of a millimeter (1.0mm) and in large proportions, typically up to 60vol%. The measured IF (internal friction) shows that the damping capacity of porous Cu is higher than that of its bulk metal. It’s found that two IF peaks present at the internal friction against temperature curves at around 280°C and 400°C.The high-temperature arises from the relaxation of grain boundaries. The low-temperature peak may origin from the interaction of dislocation and grain boundaries. TEM observations showed the dislocation substructures exist in the porous Cu. Based on the observed experimental phenomena, a four-parameter mechanical model was used for describing the operative damping mechanism of the low-temperature peak in the porous Cu specimen.

Abstract: With antimony trichloride, tartaric acid, sodium molybdate, hydrochloric acid, sodium silicate as the main raw material, a black chemical conversion coating treatment process was developed in the steel surface by the impregnation method at room temperature, and analyzed the films by SEM, XPS, XRD method. The results showed that: the film was a single black mass of antimony-based, and contains a small amount of Al2O3•2SiO2•3H2O crystal composite coating. It showed the crystalline structure in the scanning electron microscope, then preliminary analysis the mechanism on this based.

Abstract: This work aims at simulation of the mixing performance in the novel co-rotating non-twin screw group developed by the authors. The simulation concerns the incompressible fluid obeying Carreau flow model. Using the mesh superposition technique, the mixing performance in such novel mixing sections, as well as in the conventional twin screw groups with one and two tips, are simulated. Adopting the particle tracking technique, distributive mixing is visualized by the evolution of the mixing of a cluster of particles in addition to using the segregation scale. Dispersive mixing is evaluated using mixing index in combination with the probability distributions of cumulative mixing index. The computational results reveal that the novel screw group is superior in mixing ability.

Abstract: Ring parts of duplicate gear, double-side flange, high pressure value body, are widely used in engineering machinery, have the common geometrical characteristic of thick-wall, small-hole and deep-groove on the surface. High energy consumption, low material utilization, low productivity and poor quality exist in the current forging technology of this type of rings. In this paper, a new forming method for this type of rings named combined ring rolling (CRR) is proposed. The forming principle of CRR is introduced at first, then, a 3-D coupled thermo-mechanical FE model for the CRR process of a double-side flange ring is developed. By simulation and analysis, the feasibility of CRR technology is testified, and the evolution and distribution rules of stain, temperature, force and power in the rolling process are revealed. The results provide the guideline for the research and development of CRR technology.