Advanced Materials Research Vols. 418-420

Abstract: It’s very difficult to machine titanium alloy because of its features of small deformation coefficient, low thermal conductivity, small elastic modulus and large chemical activity. In this paper, we take titanium alloy TC4 as an example; using the finite element method (FEM) for the physical simulation of milling process, analyze the impact of some tool geometric parameters, such as rake angle, relief angle, rounded cutting edge radius etc., on chip form, cutting force, cutting temperature distribution of cutting tool and the maximum cutting temperature of rake face etc.. On this basis, we choose the best tool geometries, which can be taken as a theoretical reference for developing process plans of titanium alloy to reduce the number of tests and costs of field trials and to improve productivity.

Abstract: In this paper, the growth process of the interfaces of Mg-Al-Mg and Mg-Cu-Mg diffusion bonding layers which are prepared by the field-active diffusion bonding (FDB) process were investigated. The OM, SEM, EDS and XRD were applied to analyze the microstructure, phase components of the diffusion dissolution layer. The results show that the morphology and width of the diffusion dissolution layer were significantly affected by the electric field strength. At low temperature, the bonding layer was formed through solid state diffusion process, liquid phase existed between the two dissimilar metals at high temperature and eutectic layer was formed at the bonding interface. As for the Mg-Al couples, when the current density was 80Acm-2 the thickness of the transition layer was 120μm which was 12 times higher than current-free condition at 450°C for 50min.

Abstract: The objective of this research is to develop the surface roughness and cutting force models by using the air blow cutting of the aluminum in the ball-end milling process. The air blow cutting proposed in order to reduce the use of the cutting fluid. The surface roughness and cuttting force models are proposed in the exponential forms which consist of the cutting speed, the feed rate, the depth of cut, the tool diameter, and the air blow pressure. The coefficients of the surface roughness and cutting force models are calculated by utilizing the multiple regression with the least squared method at 95% significant level. The effects of cutting parameters on the cutting force are investigated and measured to analyze the relation between the surface roughness and the cutting conditions. The experimentally obtained results showed that the cutting force has the same trend with the surface roughness. The surface plots are constructed to determine the optimum cutting condition referring to the minimum surface roughness.

Abstract: The static recrystallization and precipitation behavior of weathering steel were studied using thermal simulation technology. The influence of temperature and interval time was analyzed and the softening percentage of static recrystallization was calculated. The morphology and distribution of precipitates were studied, and the driving force for static recrystallization and pinning force of precipitation were calculated. Results show that the higher the deformation temperature is, the faster static recrystallization proceed. Retardation of recrystallization could occur even in the early stage of precipitation. The precipitation pinning force showed a peak in the intermediate stage, and finally decreased as particles coarsened.

Abstract: Detail analysis is presented for the influence of elastic deformation on profile wall thickness, the metal flowing and stress load situation of an asymmetry multi-mandrel die. Through the combination of numerical simulation and traditional experimental design, the method on complex section extrusion dies by quantitative prediction of the elastic deformation situation, can improve the accuracy and success rate effectively. In addition, profiles can be extruded stably when the exit velocity fluctuation is under a corresponding range. Under this range, deformation stress caused by uneven metal flowing is under the critical stress, which relates to the thickness to width ratio t/b.

Abstract: Three kinds of commercially available epoxy acrylate reactive prepolymers with different molecular weight (MW) were used to formulate the UV-curable adhesives by addition of photo-initiator, reactive diluent, crosslinker and other additives as necessary. The MW of the said prepolymers were measured by gel permeation chromatography (GPC), while the structural characterization of the prepolymers before and after UV-curing was made by FTIR. Thermal stability of two kinds of UV-cured prepolymers with distinct MW and MW distribution was detected by thermogravimetric (TG) analysis.Lap shear strength of the adherents at different temperature were tested and compared with a known superior UV-curable adhesive (Loctite 3493). Adhesion strength of the adhesives at room temperature were all higher than 15 MPa which were more than the reported riveting intensity (10.3 MPa).

Abstract: In this paper, an orthogonal experiment design method has been used to optimize the resistance microwelding (RMW) parameters for the fine copper wire and SUS304 stainless steel thin sheet welds. A L25(5⁶) orthogonal array for three factors (welding current, weld time and electrode force) with five levels was used. Joint breaking force (JBF) and surface appearance were selected as the index of evaluation. The results show that welding current was the most influencing parameter on both joint strength and surface appearance, and weld time had the next most significant effect. The orthogonal experiment design method was proved to be a promising technique to obtain the optimum conditions for RMW of fine copper wire.

Abstract: Composites made of phenolic resin filled with natural graphite platelets and carbon fibers are fabricated by mechanical mixing, followed by compression molding. The flexural strength and electrical conductivity of composite are analyzed to determine the influence of phenolic resin and carbon fiber on mechanical and electrical properties. It is found that there is a marked dependence of the electrical conductivity and flexural strength on phenolic resin content. The electrical conductivity decreases and flexural strength increases with the increasing of phenolic resin loading. The presence of carbon fiber helps improve the flexural strength of composite such that 4 wt% CF increases the flexural strength of composite about 90%. However, an excess amount of carbon fiber reduces the flexural strength due to poor dispersion of carbon fiber in composite. The result also shows that the addition of carbon fiber exhibits a slight effect on the electrical conductivity of composite at low carbon fiber loadings.

Abstract: Parameters of Bingham model had been verified according to the thermal simulation compression tests of semi-solid 6061 aluminum and the equations presented by Stefan. The effects of the mold filling temperature of semi-solid slurry of 6061 aluminum during thixo-diecasting were analyzed. The results showed that such conditions of the mold filling temperature about 625°C, the injection speed changing to 2 m/s from 0.4 m/s when 60% of die cavity had been filled, were ideal to gain solidification in sequence and beneficial to get fully filled semi-solid parts with clear contour. The thixo-diecasting experiments were performed under above optimized conditions.

Abstract: The measuring temperature test, measuring force and failure test were carried out in order to research failure mechanism of cemented carbide milling insert machining heat resistant steel of 3Cr1Mo1/4V. The falling process of sticking-welding chip was observed by high-speed photograph.The failure morphology was observed and analyzed by SEM. The test result showed that adhesive failure and fatigue failure were the main invalid form. The mathematical model of adhering failure depth was built and the finite element analysis of the thermal-mechanic coupling physical field was conducted based on the milling equipment. The research result illustrated that the temperature of the cutter-chip contact region affectes the depth of adhering failure and they are no-linear positive correlation. The thermal-mechanical coupling equivalent stress inhances with the increase of temperature. The cutter will bring about fatigue failure when it adds over ultimate strength of cemented carbide.