The major reason that there is not more wide-spread use of titanium alloys is the high cost. Powder Metallurgy (P/M) represents one cost effective approach to fabrication of titanium components. In this paper one Powder Metallurgy technique, Additive Manufacturing (AM) is discussed with the emphasis on the “work horse” titanium alloy Ti-6Al-4V. The various approaches to AM are presented and discussed, followed by some examples of components produced by AM. The microstructures and mechanical properties of Ti-6Al-4V produced by AM are listed and shown to compare very well with cast and wrought product. Finally, the economic advantages to be gained using the AM technique compared to conventionally processed material are presented.
Soft magnetic composites allow for revolutionized designs of electromagnetic devices to aid in improved efficiency and reduced weight and costs, without sacrificing magnetic performance. Electrically insulated core powder are formed into toroid shapes and tested for core loss and magnetic permeability, which are desired to be minimized and maximized, respectively. Ferromagnetic powder has shown the most potential as core materials, however nanocrystalline materials are highly resistive and amorphous materials have benefits of very low coercivities. Likewise, organic and inorganic coating materials have been explored for the reduction of eddy currents to improve overall core losses at higher frequencies. The balance between properties is of the utmost concern for SMC applications.
To answer the need for efficient quality control protocols for additive manufacturing processes and materials, specific testing methods for powder feedstocks should be developed. A powder feedstock may contain some defects, such as porosities, that will remain in the final parts after the building process. X-ray tomography combined with 3D image analysis offers unique advantages over other characterization methods, such as pycnometry and metallography, in respect to quantifying internal porosity in the individual particles of the feedstock. This paper presents the effect of X-ray tomography parameters on the quality of the obtained images and its impact on the image analysis. An automated image analysis routine was also developed to allow the visualization of the pores inside the particles but also, more importantly, to quantify this internal porosity contents, as well as to provide information on the morphological features of these pores, such a size distribution, number of particles containing pores and the volume fraction of a pore inside a particle.
Multi-physical simulations are a powerful tool to gain a deeper understanding of selective laser melting as they allow analyzing the influence of process and material parameters on process dynamics and processing result.
This paper demonstrates the application of the Johnson–Mehl–Avrami (JMA) theory to study the kinetics of the age hardening process in an A357 aluminum alloy. The precipitation hardening effect was studied at various times and temperatures. The outcomes show that the hardness can be improved via time and temperature changes. It is thus concluded that time and temperature are key variables in the precipitation hardening of the alloy. According to the results, solubilization at 823 K (550 °C) and then aging treatment at 453–463 K (180–190 °C) for 12–18 h is the optimum cycle to obtain the maximum hardness. The apparent activation energy of 40 kJ/mol was achieved through the kinetic studies. Based on the practical data, it is generally possible to estimate the hardness at a certain time and temperature by an appropriate equation. Furthermore, the maximum hardness and the time required to reach that maximum can be easily predicted through a suitable calculated relationship. Experiments by means of hardness measurement have been performed to provide the relevant information to validate the model. This paper aims to present the application of this simple modeling. The novelty of this paper is obtaining an equation that could be used to predict the hardness of an A357 alloy with a good agreement with the practical data.
Hot Isostatic Pressing (HIP) is a technology that has been around for 60+ years. By using high temperature and high gas pressure, dry metal and ceramic powders can be consolidated and a volume decrease can be achieved. Later developments include rapid cooling and rapid quenching to enable higher productivity and high-pressure heat treatment. This paper shows the advantages of having HIPing and Heat Treatment combined for Powder metallurgy parts.
The ornamental rock processing is carried out mainly using diamond tools. These are currently being produced by powder metallurgy (PM) techniques from diamond and blend powders. In view of the diversity of materials processing routes available, natural materials, and the different processes used in rock processing, diamond tools best suited to each material require formulation of specific compositions capable to achieve suitable performances at a cost as low as possible.
What do you do when you need to design energy or weight saving part for an aerospace, marine, automotive or robotics system and the perfect material is not available? Desirable properties not normally found in an off the shelf material. Properties for example low density, high strength, high modulus and low coefficient of thermal expansion (CTE). One answer is to select several materials that have the desired properties and mix them together to produce an engineered material with the combination of desired properties. This is primarily how composites are designed, including metal matrix composites (MMCs). One lightweight MMC system specifically aluminum-SiC MMCs is described in this article which combine a low density moderate strength ductile aluminum matrix with a low CTE, high strength silicon carbide reinforcement.
Powder methods are highly applicable for the processing of more challenging metals and forms. Examples of materials that encompass both of these are metallic foams, which are advanced materials that consist of a network of interconnected or randomly spaced macropores separated by dense or microporous cell walls. These macropores can be either open or closed, or mix of those two, depending on the manufacturing process. One popular metal foam that has received a huge amount of interest in the last decade is Ti foam, due to it offering a unique combination of properties, such as high strength to weight ratio and high permeability combined with excellent biocompatibility. In this study the use of metal injection molding of titanium powder in combination with a space holder (to create large pore spaces) is examined for the production of open pore Ti foams for biomedical applications. Potassium chloride with two different particle shapes (spherical and cubic) was used as a space holder. It was found that feedstocks prepared with spherical KCl particles had a lower viscosity and better flowability compared to those made using cubic particles. Ti foams with a total porosity of 61.25% ± 0.29 were successfully produced. The structure of the foams produced was characterized using SEM and X-ray micro-computed tomography.
Boron-carbide-reinforced aluminum matrix composites are widely used as various function materials. This paper aims at reviewing theoretical and experimental background related to boron-carbide-reinforced aluminum matrix composites. The powder milling processing, solid sintering, thermo-mechanical processing and the effects of reinforcement particle size on the microstructure and morphology evolution of the aluminum matrix composites are reviewed. The formation of interface between boron carbide and matrix and strengthening mechanisms of the boron-carbide-reinforced aluminum matrix composites are discussed.
A novel sintering technology based on high density electric currents and sintering cycles shorter than a second is presented. Data will be shown that compare it to Hot Pressing and Spark Plasma Sintering and to conventional Press and Sinter. Considerations will be made on the materials, the physical and mechanical characteristics of the objects produced, on the range of present and future products, on the tooling and on the productivity.
This paper reports the activities carried out at the Department of Applied Science and Technology of Politecnico di Torino about Titanium Aluminide alloys for aerospace and automotive applications processed by the Electron Beam Melting (EBM) Additive Manufacturing technique. In particular, it describes the material characterization and the heat-treatments performed on different γ-TiAl alloys in order to improve their properties in view of their final applications.
Selective laser metal sintering is set to enable a burst of creativity for today's young gas turbine design engineers. Unconstrained by the rigours of conventional manufacturing techniques, this freedom of expression is expected to lead to a host of advances that will make power generation both more efficient and lower cost.
As additive manufacturing becomes a highly utilized system for research based projects and industrial applications, developments will be made to optimize machine capability and productivity. One of the main topics of development focuses on the quality and characteristics of the powder material used in the system.
Most industries today have waste or side streams that are deposited or sold as bi-products. Industries that are cutting and grinding silicon metal, such as the photovoltaic and semi-conductor industry, are depositing valuable metal powder materials. ReSiTec has worked on research projects for several years and developed new technology for recycling and purification of valuable metal powders. The focus has been silicon metal powder from cutting and grinding production. The process has been developed to collect fine particles, with a size range of 0–150 μm, from highly diluted waste water. Furthermore, known separation and classification techniques for metal powder processing have been adapted with the purpose of purifying and upgrading silicon metal powder from waste to new products. The tests performed were successful and the results showed an increase in purity level from 50% to >99% metallic silicon and an acceptable yield. It is believed that this new technology can be suitable for similar types of industrial metal powder waste streams. Today, ReSiTec is supporting the process industry with R&D services and is producing more than 500 tons per year of recycled, high-purity silicon metal powder.
Brazing can be considered as an attractive method for joining sintered steel components since it can be integrated into the sintering process. The behavior and quality of the joint rely on the braze filler design. Among others, the interaction between the base material and the filler depends on the brazing temperature, wettability, infiltration ability, holding time, and sintering atmosphere. The use of this joining technique in components based on Fe Cu C is very common, and in this case the presence of a second liquid phase during sintering can limit the response of braze fillers. In this study, with the aim of analyzing the effect of the base steel composition, a Ni Cu-based brazing will be used together with different Fe-base substrates for sinter-brazing tests: iron is considered as the reference, Fe C to assess the carbon addition effect, and finally Fe C Cu substrate tries to explain the interaction between the two liquid phases (the molten brazing alloy and the Cu transient liquid phase). Characterization of the final joint is supported with SEM and LOM microscopy, and EDS is used for determining the distribution of the alloying elements. Moreover, liquid phase features such as infiltration capacity and diffusion are evaluated by using image analysis. On the other hand, the study is completed with wetting evaluation of the brazing alloy.
The Gustavsson flow meter (including standard ISO-13517) is in this paper used to measure flow rate of fine AM powders. In the current paper, the results are compared to the Hall flow meter and a Freeman FT4 powder rheometer in terms of success of measuring these AM powders. The range of possible powders to measure is smaller with Gustavsson flow meter; but in this range, the difference in flow time is greater compared to the Hall flow meter. Compared to using the rheometer, the Gustavsson flow meter is faster and simpler to use; however, other powder-aspects are evaluated since little correlation was found. For the powders in this paper, all methods of characterizing the flowability could distinguish between (1) two alloys, and (2) if the alloys were new or used (in SLM), and (3) if they were dried or non-dried.
The current study reports on the effect of the addition of Al metal and secondary refractory carbides on the microstructure and mechanical properties of Ni bonded NbC matrix cermets. Powder mixtures were pressurelessly sintered for 1 h at 1420°C in vacuum. Microstructural and elemental mapping of the sintered cermets were performed by electron probe microanalysis (EPMA) to reveal the effect of the additions on the NbC grain morphology, grain growth and binder composition. Results indicated that NbC grain growth was suppressed and a homogeneous NbC grain size distribution was obtained in the cermets with the addition of Al and secondary carbides, i.e. Mo C + VC + WC, as compared to the pure Ni binder. The liquid phase sintered NbC-12 vol% Ni cermet had a Vickers hardness (HV ) of 1130 ± 22 kg/mm and indentation toughness of 11.8 ± 0.4 MPa m . With the addition of 4 vol% WC-4 vol% VC-4 vol% Mo C, the hardness increased to 1490 ± 15 kg/mm , whereas the corresponding toughness decreased to 9.2 ± 0.4 MPa m . Addition of 4 vol% Mo C into WC-13.8 vol% Ni-52.3 vol% NbC mixture further increased the hardness to 1620 ± 19 kg/mm in combination with a moderate fracture toughness of 7.7 ± 0.2 MPa m .