As the demand for miniature products has increased significantly, so also has the need for these products to be produced in a rapid, flexible and cost efficient manner. The application of electroplasticity shows significant potential to produce the components by using powder materials. Nevertheless, previous research has shown that there are still significant challenges to be met in order to achieve increased relative densification of product samples and simplification of the processes. The process concept in this study comprises the combination of electrical-field activated sintering and forming processes. Therefore, the aims of the research were to develop the process concept for the manufacture of micro- components and to design the die sets along with other tooling for machine setup to enable the forming of micro-components from powder materials. A comprehensive literature review on micro-manufacturing, size effects, powder metallurgy and the electroplasticity process has been conducted. The development of the die sets for the process has been described, followed by a series of experiments. The FE thermal-electrical analysis was also carried out to study the heating flows of the die sets development during the process. In this research, titanium (Ti) and titanium tin alloy (90Ti10Sn) have been selected for the main powder materials tested for both vacuum and open-air process environment by using a Gleeble ® 3800
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With the development of microminiaturization in manufacturing, the demand of micro-parts is increased. The preparation methods which can prepare micro-parts with excellent properties and high accuracy attract researchers’ attention. Recently, Yi Yang et al. proposed a new manufacturing technology named as Micro-forming Fields Activated Sintering Technology (Micro-FAST) for the preparation of micro- parts [1, 2]. Figure 1 shows the schematic of Micro-FAST. Loose powders were directly placed into a die, and then heated to the sintering temperature by passing an AC current through the die, and pressure is applied onto the powders at the same time.
Abstract. For the purpose of extensive utilization of powder metallurgy to micro/nano- fabrication of materials, the micro gear was prepared by a novel method, named as micro- forming fields activated sintering technology (Micro-FAST). Surface-cleaning of particles, especially during the initial stage of sintering, is a crucial issue for the densification mechanism. However, up to date, the mechanism of surface-cleaning is too complicated to be known. In this paper, the process of surface-cleaning of Micro-FAST was studied, employing the high resolution transmission electron microscopy (HRTEM) for observation of microstructure of micro-particles. According to the evolution of the microstructure, surface-cleaning is mainly ascribed to the effect of electro-thermal focusing. The process of surface-cleaning is achieved through rearrangement of grains, formation of vacancy, migration of vacancy and enhancement of electro-thermal focusing.
Increased demands on the micro-/miniature-components due to miniaturization of products and systems have been a driver to the development of micro-manufacturing technology recently. Nevertheless, the challenges are still on dealing with size-effect related issues, improving product quality, delivering multi-material processing capabilities, and addressing all of these with low-cost . At the same time, Manufacture of miniature and micro- components with traditional fabrication techniques for micro-electronics (e.g., photolithography, deposition and etching processes) as well as with micro-machining and forming is not always adequate since only a very limited range of materials could be processed with a particular process, while other manufacturing methods such as conventional sintering and metal-powder injection moulding would need longer process chains. Therefore, Micro- FAST – a novel process used to produce miniature/micro-parts directly from loose powder by combining Field- activated Sintering Technique (FAST)  and Micro-forming, was developed with a view to addressing the issues raised above. It has been demonstrated that the process is particularly suitable for forming micro/miniature components due to using very high heating and cooling rates and is of high flexibility for processing different powder-materials. To-date, high-quality parts and high process efficiency for forming with various powder-materials have been achieved [3-6]. This paper reports latest development of this processing technology by describing the recent results obtained and the understanding developed, regarding the process parameters, particle deformations and densification mechanism. The latest work particularly concerns extension of the previous research to a much wider range of the materials and component-forms that had not been addressed before.
A novel Micro-forming technology, called electric-field activated sintering for micro-scale forming (Micro-FAST), was introduced for the forming of micro-components. The effect of particle size on densification is revealed for copper powder being sintered under the influence from electrical field and force-field during forming of micro-components. Three kinds of copper powders of different particle sizes ((i) average particle size of 0.5μm; (ii) average particle size of 30μm and (iii) the mixture powders with 20% weight of 30μm and 80% weight of 0.5μm) with no binder were used for the experiments. The results show that the density of the compact sintered with mixed copper powders is the largest due to more volume of liquid phase was formed in the particle's contacts. The result being in correspondence with the analytical results of computer simulation. The new understanding developed would help to better quality control during the sintering of micro-components.
soaking time. A chemical reaction is depended on the temperature. All samples were sintered at the same sintering temperature 1100 ◦ C, so there is no difference about the reactions types conducted during Micro-FAST sintering with different soaking time. Furthermore, the long soaking time can induce the full chemical reaction between the components. Single NiTi phase is desirable for the NiTi alloys with remarkable properties. While the reaction temperatures of Ni 3 Ti and NiTi 2 are lower than NiTi. The
of the punch and the die must be less than that of the powder material being tested. to prevent any stuck between the punch and the die or sample becoming stuck during the ejection process. In addition, by using graphite, a higher sintering temperature can be used (up to 2500 °C or more). The graphite material has a low mechanical strength at high temperature is a major issue, a higher forming pressure cannot be applied during the electrical field activated sintering process [9, 10].
Abstract. As demands on miniature products increase significantly, a rapid process and production system for high-throughput, highly flexible and cost-efficient volume production of miniaturised components made from a wide range of materials is needed. A novel and electrical-field-activated sintering and forming process shows the potential to produce solid parts from powder material without any binder. Using titanium (Ti) and titanium alloy (90Ti10Sn) powder material, several processing parameters have been investigated, such as pressure, heating rate, heating temperature and holding time, which helped to contribute to the optimum result. In this study, using graphite dies, graphite punches and tungsten carbide punches, solid samples were produced, having a cylinder shape of Ø4.00 mm × 4.00 mm. Several properties of the solid Ti and 90Ti10Sn samples, such as density, hardness and the microstructures, were examined, and these showed that good results have been obtained.
In recent decades, the development towards miniaturization of products and devices in industries such as electronics, optics, communications, etc. has increased the demand for metallic parts manufactured at micro-scale. Such parts encompass a wide variety of geometries, materials, functionalities and production processes. Examples of micro-parts include screws, fasteners, connector pins, springs and micro-gears. During the last 10 years, various micro metal-forming processes have been studied and used to produce a variety of micro-metal-components  and these efforts were highlighted particularly by the EU large-scale integrated project MASMICRO which researched and produced various manufacturing facilities for micro-manufacturing  as well as recently funded EU Micro-FAST project for the development of an integrated system for volume production of micro-components by combining micro-forming and electric-field activated sintering (http://www.micro-fast.eu/).
More recently, a sintering method named as coupled multi- physical-fields activated sintering technology  was put forward for the sintering of WC-6Co cemented carbides. The ‘‘coupled multi-physical-fields’’, in this case, means that mechanical force, temperature field and electrical field are acting and superimposed simultaneously, for promoting the material’s densification process. The method has merits such as low sintering temperature, short forming time, and remark- able inhibition of particle growth without addition of inhibitors. Using this novel method, Huang et al.  successfully fabri- cated WC-6Co cemented carbides with a density of 97% achieved at a sintering temperature of 850 °C. However, in their work, effects of the processing parameters on the microstruc- tures and mechanical properties were not explored. As numer- ous reports indicated, the final, WC particle size strongly depends on the sintering temperature to be used and mechanical properties of the cemented carbides are largely dependent on the particle size of the WC formed. Therefore, in this study, we aimed at fabricating WC-6Co cemented carbides using coupled multi-physical-fields activated technology and investigating effects of sintering temperature on the densification, microstruc- tures and mechanical properties of the samples.
electrical insulator. The Alumina is being used widely in the industry. Several research the sintering of Alumina using the conventional hot pressing process or spark plasma sintering (SPS). However, these methods are and have their own limits and disadvantages, such as long process chains and low efficiency with the processes and, rarely developed for the forming of miniature and micro-scale components. In this study conducted in the report. A new process has been used adapted from the electric-current activated sintering techniques (FAST) and it is been combined with micro-forming technology and called the (Micro-FAST). The Alumina powders were loaded directly into the die, followed by electric-sintering under certain pressure. In this paper Ø4.00mm × 4.00 mm and Ø2.00mm × 2.00 mm cylinder solid samples were produced. This experiment was conducted by use of a Gleeble 3800 thermal- mechanical simulator. Several properties of the solid samples, such as relative density, ESM and EDS, were examined, and these showed good results have been obtained.
Recently, a new sintering method named as coupled multi-physical fields activated technology has been put forward for the forming of WC-6Co composites due to its significant characteristics such as lower sintering temperature, shorter forming time, and remarkable inhibition of grain growth without addition of inhibitors (Ankang Du, 2012). Using this novel method, Huang et al (2013) successfully fabricated WC-6Co cemented carbide of which the density could reach over 97% with the sintering temperature of 850℃. However from the microstructure of the sample, it can be seen that there are some holes in the samples, which have bad influences on the mechanical properties of the sample. Thus, it is necessary to further investigate the effect of higher sintering temperatures to eliminate these holes and obtain denser compacts.
Copyright to IJIRSET www.ijirset.com 1829 Microwave roasting was carried out in a microwave at 200 GHz, which has been converted from a commercial microwave with a turn table of 900 W. In order to carry out roasting, a zirconium cylinder is placed at the centre of the Table. During each experiment 10 pellets from each size were placed inside the cylinder. Zirconium Cylinder is used for such studies as primarily, Zirconium is a good absorber of microwave radiations which accelerates the preheating process of the pellets and as a thermal insulator it will not radiate the heat outside the cylinder and will maintain a good roasting environment. During the experiment, sufficient care was taken to assure that temperature is well controlled, radiation is continuous and uniformity is maintained to provide heat to each pellet under consideration. Temperature was measured using a Pt-Pt-Rh thermocouple, inserted from the top of the microwave and touches exactly the heating surface of the cylinder. In order to study the comparative phase changes between microwave roasting and conventional sintering, the pellets were sintered in a carbolite furnace and the heating rate was maintained continuous. In this study, the samples were kept in graphite crucible. The sintered sample densities were measured by weighing methods. The Tensile Strength were tested using an universal testing machine with a loading rate of 0.8 mm /min and calculated using the mathematical relation.
11 ceramic grains, and this is accompanied by densification and reduction of porosity. Therefore, shrinkage occurs in the polycrystalline material in addition to the shrinkage that has already occurred in drying. Sintering in ceramics is basically the same mechanism as in powder metallurgy. In the firing of traditional ceramics, certain chemical reactions between the components in the mixture may also take place, and a glassy phase also forms among the crystal that acts as a binder. Both of these phenomena depend on the chemical composition of the ceramic material and the firing temperatures used.
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the hardness. The eﬀect of pulsed magnetic ﬁeld on the hardness of sintered sample was similar to that on the sintered density shown in Fig. 2. The hardness of sintered sample mainly depends on the sintering suﬃciency, and its relative density and microstructure. By coupling pulsed magnetic ﬁeld, as described above, the sintering temperature increased, and insultingly the sintering became more suﬃcient, the sintered density rose and the microstructure of sintered sample was more homogeneous. So, the hardness also increased. The decrease of hardness with more intensive pulsed magnetic ﬁeld was attributed to over-high sintering temperature. Figure 5 also shows the uniformity of hardness in the radial direction of sintered sample. Especially for the sample sintered only by SPSing, the hardness at the centre was substantially higher than that at the rim on the same cross section, due to the heat loss produced by heat conduction, radiation and convection at the outside surface of sample in sintering. Coupling a pulsed magnetic ﬁeld also can improve the homogeneity of hardness because of facilitating a uniform sintering temperature distribution in the radial direction by the ‘‘skin eﬀect’’ of the induced electric current. When the magnetic ﬁeld strength increased from 0 to 2.36 MAm 1 , the bending strength was maximum, being 1235 MPa (see Fig. 6), which is similar to the change trend of the hardness. Obviously, a pulsed magnetic ﬁeld coupled Mo
Because doped PZT (54/46) piezoceramics are polycrys- talline, their microstructural characteristics (grain size and orientation distribution, phase distribution, phase and domain morphology) as well as their defects (atomic structures of domain walls, native defects, impurities) play crucial roles in determining their properties . Usually, some of these factors act simultaneously, mak- ing the polarization switching phenomena very intricate. The local densification effect  is one of the most im- portant technological problems related to sintering, as a strong densification may occur in some parts of a porous body while large pores appear in others. This shows the instability caused by initially-small heterogeneities in the spatial distribution of pores, and may lead to various microstructural defects nucleation producing macro- scopic lattice and damage. A non-uniform density distri- bution provoked by sintering instability may cause poor
deal of attention due to its incredible proton conductivity, its ability to withstand acidic atmospheres, and small activation energy requirement. Unfortunately this promising electrolyte suffers from poor conductivity at the grain boundaries and its difficulty with densification during the sintering process. With regards to densification, BZY requires high sintering temperatures for long time intervals; wet chemical synthesis has since become a common method for partially reducing these sintering temperatures. Using a new sintering method to induce a transient liquid phase within the studied material, it may be possible to reduce sintering temperatures without the use of complicated wet chemical synthesis, or significantly affecting the mechanical strength of the material. To determine whether the transient liquid phase sintering method can be utilized as a potential method for electrolyte synthesis, the chosen material, BZY20, was characterized using a number of common testing methods.
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TEM images of the samples showed in Figure 7, and the shape of the grain indicated uniformity in any sam- ples. Furthermore, morphology was improved at the sintering temperature of 750˚C compared with at 700˚C, and facets in the grain were observed by a crystal growth. The morphology have been reported about the synthe- sis by using nano-particle or nano-wire TiO 2 , which have described that the nanoparticle or nanowire Li 4 Ti 5 O 12
Increasing the amount of aluminium metal within the precursor powder in excess of the stoichiometric amount appeared to benefit the nitridation reaction, as the percentage of weight gained by the materials during sintering increased with increasing aluminium in the precursor powder, up to a maximum of 13.1 wt% total Al (4 wt% above the stoichiometric amount), Fig. 1(b). Above this composition, however, the continued increase in precursor Al content, resulted in a drop in weight gain (approximately 3%) which continued to decrease as the Al precursor content was increased further,
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specimens result in increasing of strength and crack growth resistance, which values enhance with increasing of sintering temperature. Otherwise the hardness of hot forged intermetallics decreases after their sintering. The influence of modes of treatment on the structure and properties of the materials was investigated. It has been established that the strength and fracture toughness of the intermetallics obtained from milled blend after hot forging had the higher values as compared with the alloy made from the batch without its milling.