Net Shape Parts Research Articles

Powder injection moulding of an Al–AlN metal matrix composite

A powder injection moulding process for producing fine AlN particle reinforced aluminium matrix composites was developed. The process is a promising low-cost technique for net shape production of complex aluminium metal matrix composite components. Net shape parts of near full density with good strength and ductility were produced. The AlN reinforcement particles exhibited good compatibility and were uniformly distributed throughout the AA6061 matrix. An Al–AlN composite/Al hybrid was also successfully produced. The hybrid parts exhibited good interfacial adhesion and were free of distortion.

Thermal fatigue behavior of an iron-based laser sintered material

Direct metal laser sintering is a rapid manufacturing technique to make intricate and near net-shaped parts. An iron-based laser sintered metal was studied to evaluate its thermal fatigue properties. The test was performed using cylindrical specimens in a high power induction heating system equipped with a laser strain gauge for a contactless surface strain measurement. Initiation of thermal fatigue cracks occurred preferentially at pores and layer interfaces, while propagation of cracks followed along phase boundaries and thin inter-dendritic phases and showed an inter-granular fracture. By using the fundamental Fourier equation for heat conduction, the temperature cycle was modeled and calculated. A thermo elastic ideal plastic model was used to deduce the thermal stress based on surface strain experimentally measured. Finally, the temperature distribution, thermal stresses and mechanical strains were discussed with respect to thermal fatigue damage.

Thixomolded magnesium alloys: Strategic product innovation in automobiles

The research on magnesium alloys for structural lightweight applications is today at an embryonic stage, but these alloys offer great potential. Thixomolding of magnesium alloys for automotive applications is promising since the process can be used to manufacture net-shape parts cost-effectively and with high reliability and repeatability.

Effective Stochastic Simulation for the Optimization of Time, Costs and Quality in Cold Forging

In cold forging tool life is limited in most cases by fatigue and characterized by distinct scatter depending on the scatter of the process parameters. This fact is also obstructing the production of net shape parts. Due to the scatter, a single simulation run with average values is known to be not appropriate to predict the desired output quantities. This paper describes an innovative method using a mathematical model of the forging process with a deterministic and a statistical component. According to the strength versus load concept (SVL-concept), a combination of the parametric and the statistical model leads to an integrated statistical process model which enables tool life prediction by taking statistical effects into account. In order to improve tool life an approach of avoiding tensile stresses and strains in the die has been successfully used for steel and cemented carbide tools.

High Pressure Integral Foam Moulding of Aluminium – Process Technology

The process technology for the production of net-shaped aluminium parts, which contain a foamed core surrounded by an integral solid skin, is presented. The process - an adaptation of processes used for the production of polymer integral foam parts - is realised on a pressure die-casting machine. The necessary changes in the sequence control of the pressure die-casting machine and the mould design are presented. The influence of different blowing agents and processing times on the foam structure are discussed.

Direct rapid high-temperature alloy prototyping by hybrid plasma-laser technology

Direct metal or end-use-material prototyping technology has received widespread attention in the world. However, it is difficult to obtain the full density metal or high performance specialty material parts only by using laser beam at present. The authors have thus conducted development research of direct and rapid plasma deposition manufacturing (PDM) by using plasma arc beam, but there are some problems such as the part accuracy and surface state are required to improve, and the energy is insufficient to melt high-temperature alloy and refractory materials perfectly if using micro-plasma arc gun although it is able to gain near net shape parts. In this paper, a new direct and rapid metal prototyping technology by using hybrid plasma-laser deposition manufacturing (PLDM) is developed for obtaining near net shape full density and good surface intractable high-temperature alloy prototype. Unlike PDM technology, a laser beam is entered into the plasma arc beam as assisting heat energy, and added for surface modify. In this study, attempts are made to improve part accuracy, basic performance of surface and inner. The results show that the laser beam can diminish the molten pool diameter, enhance the stability of the plasma arc beam, improve the surface state and make plasma arc-igniting easier. The inner layer of the part fabricated with this process has no porosity, and the deposition layers are metallurgical bonded. Thus the PLDM technology is able to overcome the shortcomings of existing RP and RT, and can be used for direct refractory and intractable materials prototyping.

Electronic packaging materials prepared by powder injecting molding and pressure infiltration process

AlSiCp (65 vol.% SiC) electronic packaging materials were manufactured by powder injection molding (PIM) and pressure infiltration process in order to obtain near net-shaped parts. SiCp preformed compacts obtained by pre-sintering process at 1150 K have high strength and good appearance, and the ratio of open porosity to total porosity is nearly 98%. The relative density of composites is bigger than 99%. The thermal conductivity of AlSiCp composites fabricated by this method is 198 W.m −1.K −1, and the coefficient of thermal expansion (CTE) is 8.0 x 10 −6/K (298 K).

Manufacturing of multi-functional micro parts by two-component metal injection moulding

Several metals and alloys can be used to enhance the mechanical and physical properties of micro parts and components for micromechanical, micro-chemical or sensor applications. Such parts can be produced in series by the powder metallurgical process of micro metal injection moulding (μ-MIM). This paper describes a novel manufacturing route for metallic multi-material micro components, two-component micro metal injection moulding (2C-μ-MIM). Similar to “two-colour” injection moulding of plastics, the process allows the integration of multiple functions in a micro part by simultaneously injecting and joining two materials in one mould. Net-shape parts with solid material interfaces are obtained. In this paper, the 2C-μ-MIM process is exemplified for the combination of a non-magnetic and a ferromagnetic stainless steel (316 L and 17-4PH). It is shown that intact material interfaces of less than 500×500 μm2 can be achieved by careful selection and tailoring of metal powders, injection moulding and co-sintering parameters.

Development of Cup-Cast Method; Semi-Solid Slurry Preparation without External Stirring Force

Semi-Solid metal (SSM) processing is now considered a commercially successful manufacturing route producing millions of near net shape parts per annum for the automotive industry. Although semi-solid process is currently widely used as a manufacturing process which produces near net-shape metal component, the processes those used for the preparation of semi-solid slurry still take a great deal of time, energy and money. Cup cast method – recently developed by the authors – is able to make semi-solid slurry preparation as easy as pouring water from a pitcher into drinking glass. In this method globular solid particles are prepared by controlling the turbulence and heat distribution in the melt through pouring instead of applying certain external stirring forces, in other common method. In the current study, cup cast method applied to Al-A356 alloy using simple cylinder. Vital factors of this method were optimized by investigating micro-structures.

Characterization of an iron-based laser sintered material

Direct Metal Laser Sintering (DMLS) is a relatively new rapid tooling technique to fabricate near net-shaped parts. Properties of DMLS parts are governed by their microstructure. Hence, characterization of microstructure is of significant importance. In this study, a new iron-based DMLS material was characterized to unveil its metallic microstructure to support the prediction of end-user performance and the development of new applications. Characteristics of powder particles, roughness and topography of sintered surfaces, and microstructure of sintered body were investigated. The original powder composition, the particle size, particle morphology and processing parameters were discussed relative to the sintered phases, the porosity and the microstructure. We found a microstructural waviness existing in the DMLS material. Some possible reasons are discussed.

A cyclic process for the nitridation of Si powder

The presence of coarse Si particles contributes a hindrance to achieving fully reacted Si 3N 4 by a reaction-bonded silicon nitride (RBSN) technique for use in real net-shape parts, such as turbo-charger rotors. A new process is described, in which the nitridation rate is enhanced by cyclic heating and the cyclic and isothermal heating processes were compared. When the nitridation was conducted at various temperatures and times (1370–1420 °C for times up to 60 h), the reaction rate of the cyclic process was three times faster than that of the isothermal reaction. This can be attributed to the cracking of the reacted Si 3N 4 shell during nitridation, which exposes unreacted liquid Si in the core. Cracking was found to occur by the internal stress resulting from the volume mismatch between Si 3N 4 and liquid Si.

Control of high solid content yttria slurry with low viscosity for gelcasting

In order to fabricate ceramics using yttria powder which is an expensive rare earth compound, it is necessary to employ near net shape technique, such as gelcasting. Gelcasting, a technique which utilizes in situ polymerization of acrylamide monomers, needs high solid content slurry. However, slurry preparation is difficult because fine particles aggregate easily. This investigation was aimed at studying the effects of amount of dispersant and specific surface area on the dispersion of aqueous yttria slurries, using a rheological measurement. The viscosity measurement of 45 vol% slurry prepared from smaller specific surface area particles of yttria indicated that dispersant dosages of 1.45 mass% will give the lowest slurry viscosity. Near net-shaped parts of yttria have been successfully formed by gelcasting, using this slurry. The green bodies obtained were practically no cracks.

Influence of Process Conditions of Thixomolding<sup>®</sup> on the Microstructure of Magnesium Mobile Phone Housing

Thixomolding® is a new process of net shape parts for magnesium alloys in one step, and it is suited to manufacture the thin wall products, especially to the electronic component shells. In this paper, the sample of mobile phone housing is fabricated by 220Tons Thixomolding® machine made by Japan Steel Works. The effects of barrel temperature, screw rotate rate and mold temperature on microstructure were studied. The relationship between process parameters and microstructure was also discussed in this paper.

Use of a Naphthalene-Based Binder in Injection Molding Net-Shape Titanium Components of Controlled Porosity

We have recently developed a naphthalene-based binder system for use in powder injection molding (PIM) of ceramic and metallic materials. The use of a binder that can be removed via sublimation offers several unique advantages relative to the typical thermoplastic and/or thermoset binders employed in PIM. One of these is that essentially no volume change takes place during debindering. This offers a relatively facile method of introducing porosity into a net-shape part of potentially complex geometry. In the study described in this paper, the effects of powder loading and subsequent isostatic compaction on the size and amount of porosity in the components produced by this technique were investigated. In general, it was found that the amount of porosity is inversely proportional to the initial concentration of metal powder in the PIM feedstock. Likewise, average pore size displays a similar relationship with powder loading.

Simulation of Solid State Sintering through FE Modeling for the Optimum Design of 3D Parts

Modelling of sintering provides an effective assisting tool for process optimisation and accurate design of near net shape parts. In this paper the shrinkage and shape changes of 3D real components are simulated during solid-state sintering through a combination of a multi-physics microscopic model and a macroscopic FE model. The computed stress and temperature fields allow for prediction of sinter distortions with the aim of minimising them and help in manufacturing of near net shape parts. The model results are in good agreement with literature data.

Influence of container on numerical simulation of hot isostatic pressing: final shape profile comparison

Hot isostatic pressing (hipping) is a manufacturing process capable of producing mechanical parts in only one operation by the hot forming of metal powders. The aim of this process is the production of net shape parts notably for aeronautics or nuclear applications. In the past, the trial and error method was used in order to find the right container and insert geometries giving the net shape parts. Several prototypes must therefore be manufactured before a successful conclusion is reached. This forming procedure results in expensive developing costs due to the quasi unitary production, pressure and temperature environment and the high temperature tooling involved.Numerical simulation raises hopes on the optimisation of this manufacturing process through the use of viscoplastic constitutive equations implemented in the finite elements software PRECAD/M.The rheological functions of this viscoplastic model are usually determined by assuming that the mean pressure in the sample is homogeneous and equal to the external applied pressure. The numerical simulations of hipping experiments show that this assumption is often false: pressure is partially transmitted to the powder because of the container rigidity. New rheological functions have been determined with the stress values obtained by numerical simulation of these tests. The new numerical simulations are then in better agreement with the experimental values and the prediction of an industrial complex part final shape is also improved.

THIXOMOULDING INJECTION MOULDING OF SEMI-SOLID MAGNESIUM ALLOYS

The thixomoulding technology, i.e. the injection moulding of thixotropic, semi-solid magnesium, represents a new, innovative and fully automated processing technique for magnesium alloys, which combines substantial processing elements of the magnesium die casting and the conventional plastics injection moulding. The process technology is very similar to the injection moulding of thermoplastics, except magnesium is being moulded. The two objectives pursued by thixomoulding are the process substitution of die casting of certain component parts on the one hand and the material substitution in special fields of plastics injection moulding on the other hand. Magnesium offers a considerable potential for material and structural lightweight construction. Thus, by means of the thixomoulding technology, a multitude of lightweight and mechanically high-grade net or near net shape parts can be manufactured, requiring no or very little finishing. Thixomoulded parts can be found in the areas of consumer electronics (for example housings for cell phones, laptops, cameras etc.) and in the fields of the automotive industry (in the form of thin-walled structural components). The thixomoulding process is environmentally friendly, since small amounts of argon can be used for an inert gas atmosphere in the mostly encapsulated plasticising unit, instead of ozone depleting gases, such as SF 6 , generally used in die-casting. At the same time, the process is operator friendly as well, since the danger of exposure to molten magnesium is minimised due to the closed machine.

An Integrated Comprehensive Approach to the Modeling of Resin Transfer Molded Composite Manufactured Net-shaped Parts

An Integrated Comprehensive Approach to the Modeling of Resin Transfer Molded Composite Manufactured Net-shaped Parts

Cold Sizing of Cold- and Hot-Formed Gears

Today's markets require industrial forgers to manufacture complex near net shape or net shape parts at minimum unit costs. One way of meeting this challenge is to combine a cold or hot forming process with a subsequent cold sizing process in order to achieve the desired tolerances. In this context, a closed-die cold sizing process of a straight-toothed planetary gear has been investigated in terms of the occurring elastic die deflection which is a threat to accuracy in this and any other cold forming process. Two strategies have been employed to minimize the elastic die deflection. The first strategy consists in a correction of the die cavity's tooth profile based on the finished part's deviation from its theoretical shape determined through Finite-Element-Analysis (FEA). The key idea underlying the second strategy is an innovative tooling concept which compensates the elastic die deflection by means of a counter pressure generated by an elastomer ring embedded in the lower die. The advantages of this active concept have been confirmed in numerical and experimental investigations.

各種粉末の焼結機構と新しい焼結技術の展開 インサート射出成形法を用いたステンレス鋼（ＳＵＳ３１６Ｌ）と硬質材料の複合化

Generally, metal injection molding (MIM) process has been utilized for mass production of complicated and near net shape parts using single material. If plural materials are joined in MIM process, multi-functional compacts can be manufactured in high productivity and high quality. Joining of stainless steels (SUS316L/SUS430L) by using insert injection molding was reported in our previous paper.In this study, several hard materials were selected to join with stainless steels (SUS316L) by using insert injection molding. Especially, the combination of SUS316L and SUS420J2 showed good joining because of the diffusion of Ni and Mo from SUS316L to SUS420J2.