Powder Metallurgy Applications Research Articles

Powder Characterization Techniques

Abstract Knowledge of the characteristics of powders is of paramount importance for the successful development and application of powder metallurgy and particulate materials. Early characterization techniques were related to press and sinter powder metallurgy, dealing with the relatively coarser powders and with the analysis of individual as well as mass of powders. These analyses include structure, chemistry, morphology, size, shape, their distribution, different densities, flow, porosity, compressibility, friction, shear, residual stress, and so on to obtain a defect-free product. The advent of nanopowders and nanotechnology, metal injection molding, and more recent additive manufacturing has to deal with finer powders and different processing steps, which has resulted in the advancement of traditional powder characterization techniques to the next level, evolving newer and more innovative characterization techniques. Consequently, techniques such as x-ray photoelectron spectroscopy, scanning electron microscopy, laser light diffraction, x-ray computed tomography scan, atomic force microscopy, differential thermal analysis, etc., have been used with emphasis on powder cleanliness and internal particle porosity. The widely used industrial additive manufacturing process uses powder bed fusion that bonds successive layers of powders to facilitate the fabrication of parts with complex geometries. Thus, this article also explores the emerging trends in dynamic powder testing using a powder rheometer to measure dynamic flowability from measurement of axial and rotational forces acting on the rotating blade and the study of spreadability and flowability of powders by rotating drum instruments. A judicious selection of relevant and appropriate powder characterization techniques will ensure predictable powder behavior during the manufacturing process, resulting in consistent and reliable products.

Designs and Evaluations of a Gas Atomizer to Fabricate Stainless Steel Metal Powder to Be Applied at a Metal Injection Molding

Metal Injection Molding (MIM) is an application of Powder Metallurgy (PM) and Plastic Injection Molding currently being developed to produce precisely-small components. Most of the metal applications using PM are stainless steel fabricated by a gas atomizer. In this study, an atomizer is designed and fabricated to produce stainless steel powder by using a free fall gas atomization method. The stainless steel used in this study is AISI 304 atomized with the diameter sizes varying from about 3 mm, 5 mm, and 7 mm. The variables of diameter size results are the lowest melt flow rate produces the smallest mean diameter, but no significant difference on the sphericity of powder morphology. While the gas pressure variation results shows that metal powder with smaller size will be produced more using the high gas pressure. The gas atomizer have successfully produced metal powder with the size <40 μm and have a spherical shape. The well rounded sphericity for melt flowrate 0.41x10-3 m3/min, 1.14 x10-3 m3/min, and 2.24x10-3 m3/min are 60.0%, 36.0%, and 55.2% respectively.

Analysis Of Alumina Particles Size And Shape Formation From Developed Planetary Ball Mill

This study emphasizes and the testing of alumina particles via a fabricated planetary ball mill. The fabrication of planetary ball mill work began with the design of the machine. Parts were fabricated separately then assembled. The jar and grinding media were made up of stainless steel as it as a higher strength property than Alumina powder. Testing and calibration are carried out through the response surface methodology utilizing the experimental results. Test is also executed to confirm the validity and the accuracy of the developed planetary ball mill. Based on the result obtain, the alumina powders have a particle size reduction of about 50% of the original particle size. Furthermore, the shape of the alumina particle changes from angular to irregular particle shape. It is apparent that the fabricated planetary ball mill able to grind the alumina powders and produce ultrafine particles by given period and parameter set. The fabricated ball mill able to function better than conventional ball mill. The planetary ball mill will be useful for the laboratory use purpose and production of ultrafine powder production. This ultrafine powder production can be used in application of powder metallurgy and advanced material research purposes.

Preface

This year the Risø International Symposium on Materials Science is celebrating its 40th year jubilee. During this 40-year period, significant progress has taken place and new discoveries and understanding in the field of material science and engineering have materialized in advanced metals and alloys with wide applications in society. In parallel, there has been an unprecedented development of 2D, 3D and 4D characterization techniques operating on multiple length scales down to the atomic dimension. The development has led to revision and foundation of fundamental principles and models for example in the areas of deformation, recovery and recrystallization of metals and alloys. This in-turn has led to new and demanding challenges that are addressed in the Proceedings. The challenges include:• Transitional stages in the evolution of deformation microstructure and strengthening mechanisms.• Effects of local microstructural variations on the evolution of microstructures during annealing• 2D, 3D and 4D characterization techniques based on for example x-rays and electron microscope techniques in the laboratory and at international facilities.• Microstructural variations at different length scales which is of critical importance for the properties and performance of metals and alloys for engineering applications.• Advanced and new processing techniques of bulk materials and by application of powder metallurgy in additive manufacturing and spark plasma sintering processes.• Experimental findings in 3D and 4D used as input to as well as validation of analytical and numerical models.The metals and alloys investigated are of fcc, bcc and hcp structure, in bulk form or present as gradients or multilayer structures.The Proceedings contain 15 keynote, 11 invited and 34 contributed presentations covering the above-mentioned key themes. It is our hope that Proceedings can inspire the future development of this field.

Comparison of a commercial powder and a powder produced from Ti-6Al-4V chips and their effects on compacts sintered by the sinter-HIP method

The present paper is related to the conversion of Ti-6Al-4V chips into powder and investigates the usability of the produced powder in powder metallurgy applications. In this regard, a disc-milling process was applied to Ti-6Al-4V chips and the obtained powder was subsequently compacted. The compacted samples were sintered by the sinter hot isostatic pressing (sinter-HIP) method at 1200°C under high vacuum, their mechanical properties and microstructure were investigated and compared with those of commercial powder compacts subjected to the same preparation processes. The results showed that the produced powder exhibits greater flowability and higher apparent density than the commercial powder. However, the sintered products prepared from the commercial powder exhibited a higher relative density, lower porosity, and, as a result, greater flexural strength compared with the sintered compacts prepared from the produced powder. In addition, transgranular fracture was greater in the sintered products of the commercial powder. The microstructural studies revealed that the sintered products made from both the commercial and the produced powders consisted of α- and β-phase but contained more α-phase. All of the examined properties were found to be substantially affected by the particle size of the powders.

Reclamation of steel shots by acid leaching for powder metallurgy applications

Acid leaching is extensively employed for extractive metallurgy, but its use on reclamation of shot blasting media has not been extensively studied. The parameters of acid leaching process such as rate of stirring, the leached material grain size, the solid (material) to liquid (acid) ratio, type of acid, concentration of acid, leaching temperature, and leaching duration govern the effectiveness of this process. The goal of this article is to investigate the effectiveness of acid leaching to recover the iron from used shot blasting media. Influence of varying leaching durations on the recovery percentage of iron from the used shot blasting media is investigated, and it is found that acid leaching can remove impurities from used shot blasting media and it can successfully recover 73.6% of iron on the particle surface level and 44.3% of iron overall. Hence, it is a feasible process for recovery of iron from used shot blasting media.

Applications of Powder Metallurgy to the Production of Recycled-Iron-and-Aluminum Deoxidation Briquettes for In-Ladle Use

Enhancement of product quality and reduction of production costs/energy consumption/environmental impact for steel smelted in arc furnaces both require improvements to out-of-furnace or ladle processing, and deoxidation in particular. A production process was developed for deoxidation briquettes based on the requirement that they be highly transportable and suitable for long-term storage while complying with deoxidation efficiency specifications (deoxidizer utilization, concentration of non-metallic inclusions, and duration of deoxidation process). We show that steel deoxidation briquettes meeting shape and density requirements can be produced using powder metallurgy technology. Such briquettes provide improved entrainment with the steel during the mixing process, meaning that the briquette components are able to melt more thoroughly as they are absorbed by the molten metal.

ALUMINUM ALLOYS BY ECAP CONSOLIDATION FOR INDUSTRIAL APPLICATION

A ffecting factor of importance in industrial applications of Powder Metallurgy is a process of consolidation , t he fabrication process with the good parameters by increasing of the bond strength o n the surface to reduce the number of pores. In particular, methods of Severe Plastic Deformation (SPD) overcoming a number of difficulties associated with residual porosity in the sample which solidified. Ultrafine–Grained (UFG) materials processed by ECAP usually show unique mechanical properties such as; high yield stress at low strain hardening, good ductility on low temperatures and high strain-rate super-plasticity at high temperatures. Production of Al alloy growing rapidly, particularly in the automotive industry . Although high-strength aluminium alloys containing Mg and Si (6xxx series aluminium alloys) which are easily reached, for formability processes is not sufficient to be applied. Therefore, much research has focused on increasing the formability of these alloys through heat treatment. High strength aluminium alloy, such as alloy AA7XXX, which combines the power of high-density ratio with excellent mechanical properties, is widely used for aviation applications, superplastic forming into the high-volume fabrication of components in the automotive. Consumer products industry is currently limited because of the relatively low strain rate. AA6XXX are some of the alloys materials, mostly used currently covering the whole range of industry. Applications of AA6XXX easier to process than AA7XXX because of properties the material elasticity, AA7XXX tend to form internal cracks as a result of microsegregation. That way heat treatment is required to improve the properties of the material when it is processed by ECAP.

Application of Powder Metallurgy in Production of Biomaterials

Metallic biomaterials are currently produced mainly by conventional metallurgical processes, i.e. the melting and casting used e.g. in production of cobalt alloy implants, or forming processes as cold or hot working (rolling or forging of stainless steel for surgical applications). Such processes including melting are used also in production of smart biomaterials - NiTi shape memory alloys. The mechanical properties are strongly dependent on the grain size. Therefore, the techniques to obtain finer structure are very desirable to enhance the mechanical properties of the biomaterials and thus to increase lifetime of the implant. This paper is devoted to the description of the possibilites of powder metallurgy not only for the structure refinement, but also for the ptoduction of clean biomedical alloys as well as the porous bioamterials. The use of powder metallurgy is described for Co-Cr-Mo surgical alloy, Ni-Ti shape memory alloy and Ti-based porous biomaterial. In addtion to known methods, new powder metallurgy processes and materials developed by the authors are presented.

Порошковая металлургия при получении металлического ядерного топлива

Порошковая металлургия при получении металлического ядерного топлива

Production of copper powder form printed circuit boards by electrodeposition

During the last years, the waste electrical and electronic equipment (WEEE) are gathering attention, as a very special section of waste. In fact, they have been proven to be source for the recovery of metals. In the present study printed circuit boards (PCBs) were cut and treated thermally at 500oC for 1 h in both air and nitrogen atmosphere. The obtained material was dissolved in three different acid media HNO3aq, HClaq and H2SO4aq, in order to extract copper. The achieved Cu recovery percentages were 97.5, 65 and 76.5% respectively. Electrodeposition technique was applied in order to recover copper in powder form. More than 98% of copper was recovered achieved by application of high current density resulting to dendritic structure of copper. The applied process was characterised by a high current efficiency and led to the production of copper powder of 80 μm mean diameter appropriate for powder metallurgy applications.

Application of powder metallurgy and hot rolling processes for manufacturing aluminum/alumina composite strips

In this study, aluminum matrix composites (AMC) with 2, 4, 6 and 10wt% alumina were produced using powder metallurgy (PM), mechanical milling (MM) and vacuum hot pressing (VHP) techniques; then, this was followed by the hot-rolling process. During hot rolling, AMCs with 6 and 10wt% Al2O3 were fractured whereas strip composites with 2 and 4wt% Al2O3 were produced successfully. Microstructure and mechanical properties of the samples were investigated by optical and scanning electron microscopes and tensile and hardness tests, respectively. Microscopic evaluations of the hot-rolled composites showed a uniform distribution of alumina particles in the aluminum matrix. It was found that with increasing alumina content in the matrix, tensile strength (TS) and hardness increased and the percentage of elongation also decreased. Scanning electron microscope (SEM) was used to investigate aluminum/alumina interfaces and fracture surfaces of the hot rolled specimens after tensile test. SEM observations demonstrated that the failure mode in the hot-rolled Al-2wt% Al2O3 composite strips is a typical ductile fracture, while the failure mode was shear ductile fracture with more flat surfaces in Al-4wt% Al2O3 strips.

Mechanical properties of Sn–0.7Cu/Si3N4 lead-free composite solder

The use of reinforcing high performance ceramic particulates in monolithic lead-free solder is one way to improve the service temperature and mechanical behavior of a solder joint. In this study, various compositions of Sn–0.7Cu/Si3N4 lead-free composite solder were fabricated via the application of powder metallurgy (PM) techniques. The influences of the Si3N4 particulates in the monolithic matrix solder on the melting point temperature (Tm), microhardness value, lap-shear strength, and surface fracture mechanisms were investigated based on the weight percentage addition used (0.5wt%, 1.0wt%, and 1.5wt%). Minimal alteration of the melting point temperature of the composite solder sample was obtained. Improvements in the microhardness value and lap-shear strength were found for higher reinforcements of Si3N4 particulates, which revealed the formation of a more ductile fracture mode in the composite solder samples. The increasing addition of Si3N4 allowed the formation of homogeneous and finer dimples. Overall, the addition of Si3N4 particulates to the Sn–0.7Cu lead-free solder should be higher than 1.0wt%, as these compositions showed superior mechanical properties.

Effects of major impurity elements on compressibility of water-atomized iron powder

Compressibility is one of the most important properties of iron powder for powder metallurgy applications. Understanding effects of chemical impurity elements on compressibility of the iron powder and differentiating contribution of each impurity element are critical for the iron and steel powder enterprise to select approaches to control and improve compressibility of the powder. In this work 500 water-atomized iron powder samples are chosen and effects of the main impurity elements like C, Si, Mn, P, and S and hydrogen loss (HL) reflecting oxygen on compressibility of the iron powder are quantitatively studied. First, effect of single impurity element on the compressibility is investigated. Linear regressions show the degrees of regression are very low even with sample number increase up to 500 implying uncertainty of the single factor regressions due to the instable content of the other impurities when the effect of one impurity element is concentrated on. Then, a multiple factor regression is established taking into account all the six impurity elements as a whole. The degree of regression improves to as high as 0.9746 with sample number increase to 500 and dependency of compact density Y on the six impurity elements can be expressed as: Y = 7.1442 – 0.4231× C% – 0.0498 × Si% – 0.0988 × Mn% – 3.2784 × P% – 0.2577 × S% – 0.1220 × HL%. This equation manifests the negative effects of all the six impurity elements on compressibility of the water-atomized iron powder by P and C mostly, Mn, S, and HL moderately, and Si least.

Characterization of titanium powder: Microscopic views and macroscopic flow

Powder metallurgy is a very popular and cost effective process due to improvements in powder availability and the ability to produce a part close to the desired net shape. With the introduction of the Armstrong Process®, which produces commercially pure titanium powder, it is necessary to understand the flowability characteristics of the irregular particles produced. This paper reports the physical properties of the raw powder and a characterization of the inter-particle forces present in the poly-disperse size mixture. The titanium powder size distribution and particle morphology are determined using sieve analysis and quantitative SEM image analysis, respectively. The results demonstrate that attempts to improve the shape of the particles simply yield smaller irregular shaped particles, but with a high concentration (≈20%) of extremely fine particles that are less than 45μm. However, the microstructure of all particle sizes remains consistent with an irregular outline and a porous interior, much like coral. The inter-particle force properties are approximated by measuring the dynamic angle of repose within a rotating tumbler. Tumbler dimensions and rotation rate of the system are non-dimensionalized via the Froude number, which relates input energy to gravity driving the flow. The results confirm the increase of the angle of repose with increasing Froude number. However, the high concentration of very fine particles in mixtures that are processed to generate more round titanium powder are found to be a detriment to uniform, repeatable flow that is necessary in manufacturing processes. The overall conclusion is that narrower size ranges of titanium powders produced by the Armstrong Process® are necessary to provide useful source materials in powder metallurgy applications.

Effect of electrolysis parameters on the morphologies of copper powder obtained at high current densities

The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders at high current densities under galvanostatic regime were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was used for analyzing the morphology of the copper powders. It was found that the morphology was dependent over the copper ion concentration and electrolyte temperature under same current density (CD) conditions. At 150 mA cm-2 and the potential of 1000?20 mV (vs. SCE), porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4). Under this condition, high rate of hydrogen evolution reaction took place parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk-stock like morphology with the increasing of Cu ion concentrations towards 0.120 M, 0.155 M, 0.315 M, 0.475 M and 0.630 M Cu2+ in 0.5 M H2SO4 respectively at the same CD. Similarly, as the temperature was increased, powder morphology and apparent density were observed to be changed. The apparent density values of copper powders were found to be suitable for many of the powder metallurgy applications.

Ball-mill grinding kinetics of master alloys for steel powder metallurgy applications

The grinding kinetics of three newly developed master alloys for steel powder metallurgy applications were investigated using a laboratory ball-mill. Non-first order grinding kinetic is observed for the three master alloys as the breakage rate increases with grinding time due to the work hardening of the ductile phase in the microstructure. Agglomeration of fine particles is observed after a critical time at which d 90 reaches its lowest value (~ 30 μm). Critical times are related to the hardness and the microstructure of the different master alloys. Agglomeration of fine particles can be overcome with the use of a process control agent. In this study, the addition of stearic acid to master alloy powders prior to grinding successfully eliminates agglomeration for long grinding times (d 90 ~ 16 μm after grinding for 270 min).

JPMA development prizes

JPMA, the Japan Powder Metallurgy Association, has announced its 2010 awards for developments in the applications of powder metallurgy.

유한요소해석을 이용한 알루미늄분말단조 피스톤 성형해석에 관한 연구

Powder metallurgy processes are used to form Net-Shape products and have been widely used in the production of automobile parts to improve its manufacture productivity. Powder-forging technology is being developed rapidly because of its economic merits and because of the possibility of reducing the weight of automobile parts by replacing steel parts with aluminum ones, in particular while manufacturing automotive parts. In the powder-forging process, the products manufactured by powder metallurgy are forged in order to remove any pores inside them. Powderforging technology can help expand the applications of powder metallurgy; this is possible because powder-forging technology enables the minimization of flashes, reduction of the number of stages, and possible grain refinement. At present, powder forging is widely used for manufacturing primary mechanical parts as in combination with the technology of powder forging of aluminum alloy pistons.

The Electrolytic Production of Ti from a TiO<sub>2</sub> Feed (The DARPA Sponsored Program)

DARPA instituted an Initiative in Titanium in 2003 to produce titanium, alternatively to the Kroll process, in a billet form for under $4/lb. This DARPA sponsored program has gone into Phase II consisting of utilizing ore/TiO2 as a feed. The TiO2 is carbothermically reduced to a suboxide-carbide (Ti:O:C) which is used anodically to resupply the titanium content in an electrolysis process that deposits titanium in a powder morphology. The deposited powder is uniquely stripped from the cathodes and harvested in a separate stream that permits continuous electrolytic processing to produce titanium at an estimated cost about ½ the Kroll process. Oxygen contents less than 500 ppm are achievable with particle sizes in the desired range for powder metallurgy applications. The process has been demonstrated on a continuous basis and is in the stage of scaling-up to 500 lbs/day.