Materials Science Forum Vols. 561-565

Abstract: This paper utilized a wireless temperature sensing system to measure the temperature histories of tool and workpiece during cutting. It is essential to use a wireless sensing system to measure the temperature in cutting and monitor the cutting process due to tool movement, workpiece turning, network monitoring and safety consideration. The temperature sensing system includes the wireless transmitter and receiver, A/D and D/A converter, data processing software, and computer. The temperature histories for different feed rates and depths of cut were measured in real time during cutting. The data measured by using wireless temperature sensing system were also compared with these obtained from an infrared thermometer.

Abstract: Powder injection moulding (PIM) is a cost effective powder metallurgical process for the fabrication of small, complex-shaped components for high performance applications. A binder system, which comprises a major fraction of polyethylene glycol (PEG) and a minor fraction of a very finely dispersed polymethyl methacrylate (PMMA), has been applied for tungsten carbide (WC) – cobalt (Co) hardmetal powders. PEG can be removed rapidly by water leaching and PMMA is removed by subsequent pyrolysis when the components are ramped up to the sintering temperature. In this work, the development of feedstock formulations and of the processing parameters for a successful injection moulding and to achieve high density has been investigated. The present study has demonstrated that the binder can be employed for the production of WC-Co hardmetal components by PIM process. The maximum density achieved thus far is 97% of the theoretical value.

Abstract: Al-Zn-Mg-Cu alloy containing 2%Mn was made using spray forming method and hot extrusion. XRD, OM, and SEM were used to investigate the microstructure. Results showed that after being hot extruded and solid solution treated, the Al alloy matrix had uniformly fine recrystallized grain with an average size of 8μm. The particles of MnAl6 were formed during the spray forming process and distributed along the grain boundary. Deformation and spheroidization of MnAl6 particles were occurred during post hot extrusion and solid solution treament, which would be benefit to the improvement of toughness of Al alloy. When aged at the T6 conditions, the tensile strength of the Al alloy was increased up to 775MPa with the elongation of 4.3%, the fracture surface consisted mainly of dimples with a size lower than 500nm.

Abstract: The MgB2 PITs, prepared by filling Fe tubes with MgB2 as a core, were processed through different number of passes at room temperature via Routes A, BA, C and BC. The mechanical properties of the PITs were measured in terms of density and hardness. The extent of the compaction was also studied through shear punch test. The shape of the compacts remains circular even after four passes via Route C & BC. Higher density and hardness along with higher USS is observed from the PITs of Route C compared to Route BC. The PITs processed through Route A and Route BA did not show sufficient compaction to carryout the density measurements. Thus, the current study shows that Route C is the optimal route; to attain good mechanical properties in ECAE processed MgB2 PITs with Fe tube.

Abstract: The shot peening process can improve the fatigue strength of machine parts of aero structures. Due to the strength requirement of aircraft, the shot peening is widely used in the manufacturing process. Most of shot peening parts peened after penetrate inspection to ensure no defect and crack on the surface, and then peen the shots on the surface of machine parts to increase the fatigue life. During the first article verification period, the saturation curve has to be created. The peening parameters of mass production would base on the peening parameters of saturation point of the saturation curve. By using statistical methodology to analysis saturation curve of shot peening process, this study tries to find the relationship between saturation curve and relative peening parameters, such as peening time, air pressure. The results of this analysis can provide an efficient and economical approach for the process engineer and technician to develop the new shot peening process.

Abstract: Aqueous solutions of tin (II) chloride dihydrate and oxalic acid dihydrate were prepared and mixed using two protocols: (1) fixed former concentration and variable latter concentrations and (2) fixed latter concentration and variable former concentrations. Following filtering, washing, and drying, the precipitates were calcined and ground. The calcined powders were characterised in terms of mineralogy and the particle size and morphology of the resultant tin oxide particles and agglomerates. The morphologies of the uncalcined tin oxalate also were examined. In nine of the ten samples, the tin oxalate precipitates consisted of prismatic elongated crystals. In the remaining sample, the low concentrations of solutions probably resulted in the crystallisation of smaller equiaxed particles. Regardless of the particle size or shape of the tin oxalate, the resultant particle size of the tin oxide was ~75 nm and the morphology was consistently spherical. The consistent particle size is attributed to the low solution concentrations used. The tin oxide particles were heavily agglomerated into plates of ~0.5 μm diameter. This morphology probably resulted from the plastic deformation during grinding of the calcined tin oxide, which was likely to have been subject to surface water adsorption on the fine particles. Under the experimental conditions investigated, there were no particle or agglomerate size dependencies on the solution concentrations and mixing method.

Abstract: Aqueous solutions of tin (II) chloride dihydrate and oxalic acid dihydrate (both 0.04 M) were prepared and mixed by (1) dropwise addition and (2) instantaneous addition, with both involving addition of the latter to the former. Following filtering, washing, and drying, the precipitates were calcined and ground. The particle size and morphology of uncalcined and calcined tin oxalate were examined by electron microscopy and laser diffraction. The method of addition was important in that it influenced both the particle size and shape of tin oxalate. This resulted from the time effect of the ionic collision frequency and the proximity effect of the diffusion distance. As expected, ageing was important in that it caused grain growth and reduction of surface area of the tin oxalate. Although there appeared to be an effect of the method of addition on agglomeration of the tin oxide, this was a result of adsorption of atmospheric moisture, which depended on the relative humidity of the environment during grinding.

Abstract: We investigated the contribution to the high yield strength due to the solid solution strengthening in nanocrystalline Al-Ti alloys produced by a vapor quench method. The misfit strain due to solute Ti atom in aluminum was obtained from the first principles calculation. Then, the theoretical result of the contribution to the yield strength due to the solid solution strengthening was estimated from the misfit strain using the Friedel’s theory. In dilute Al-Ti alloy, the theoretical results of the solid solution strengthening from the misfit strain was in good agreement with the analytical result using the measured grain size and yield stress.

Abstract: Recently, requirements for structural materials become increasingly severe. A coating is one of the most promising methods to achieve the requirements. However, conventional coating processes generally have technical problems. We apply Supersonic Free-Jet PVD (SFJ-PVD) to coating. The SFJ-PVD is a technique to deposit nanoparticles with supersonic gas flow and to form a thick coating film without a crack or a void. This method is composed of “gas evaporation” and “vacuum deposition”. In a gas evaporation chamber, a source material is evaporated to form nanoparticles in an inert gas atmosphere. The nanoparticles are then carried to a substrate in a deposition chamber with an inert gas flow through a transfer pipe. The gas flow is generated by the pressure difference between the chambers and accelerated through a supersonic nozzle. With SFJPVD, We obtain uniform several hundreds micron meter-thick, high-density coatings.

Abstract: It was shown on laboratory and industrial scale that ultrasonic melt treatment (UST) significantly refines structure of aluminium alloys and improves the quality of castings. However, despite considerable efforts which have been made over decades in the field of ultrasonic processing of aluminium melts, quite a few problems remain unclear. One of them is addressed in this project. The aim of the project is to understand which mechanism is responsible for cavitation-aided grain refinement. It is expected that the knowledge gained as a result of this work can be used in directchill, shape and die casting. The paper describes an experimental setup and first results on the correlation between parameters of UST, solidification conditions and degree of structure refinement. In separate experiments, a model Al-Cu alloy with different amount of solidification sites is solidified with and without UST. The final microstructure is analyzed.