Powder Metallurgy

The possibility of producing titanium alloy Ti ? 6Al ? 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated. Various powder mixtures based on titanium and titanium hydride with alloying additions of either elemental powders having different particle sizes, or master alloys, were studied. It was shown that the synthesis of Ti ? 6Al ? 4V from mixtures of titanium hydride and master alloys is optimal with respect to the attainment of high relative density. In this case the sintered material has density up to 99%, homogeneous microstructure with relatively small (100-120 µm) ß-phase grains, and a low concentration of impurities, in particular oxygen, which provide a high level of mechanical properties s(ten = 970 MPa, d = 6%).

We review research carried out at the École Polytechnique de Montréal, over the past 10 years, on BiSbTeSe high thermoelectric performance materials. One practical result of this activity is a reliable powder metallurgy technology, combining mechanical alloying and hot extrusion to obtain P and N type polycrystalline alloys with enhanced mechanical properties. The extrusion process led to favourable crystalline texture resulting in thermoelectric figures of merit as high as 3.5 ×10-3 K -1 and 3.01 ×10-3 K -1 at room

В отходах пирометаллургического производства меди накоплено значительное количество отвальных шлаков. Даже при среднем содержании меди в них 0,30–0,80 %, видно, что потери металлы
составляет значительных. В этой связи задача создания  рациональной и комплексной технологии переработки шлаков и промпродуктов медного производства является весьма актуальной. В статье рассмотрен инновационный метод снижения потерь меди со шлаком. Для проведения этого исследования
использованы восстановительно-сульфидирующих комплексы (ВСК), состоящие из клинкеров цинкового производства и хвостов обогатительных фабрик АГМК. Полученные результаты  показывает, что внедрение данной технологии в промышленность позволит повысить комплексности использование сырья.

Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with
20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix
powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles
gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids
between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity
nitrogen gas from 565◦
-580◦C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering
density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between
matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and
mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of
Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions,
sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM
were used to characterize these materials.

Torsion extrusion (TE) process was performed successfully for consolidation of commercially pure aluminum powder at 350 °C. It was shown by a specific mechanism that the shear strains applied during consolidation of aluminum powder by the TE process have a considerable effect on the micro-structural shape of the porosities and also their omission efficiency. Density measurements showed that in the TE process a better consolidation, with respect to hot forward extrusion, was accomplished. Tensile and hardness tests results showed superior values for the ultimate tensile strength (UTS) and hardness values in the specimens produced by the TE process.

The effect of the introduction of different alloying elements to commercial pre-alloyed powders and subsequent heat treatment on the hardness, wear behaviour and microstructure was investigated. Prealloyed powders based on both Fe-Cu and Fe-Cu-Sn systems were used as starting powders. Master alloy additions were included in these systems. Green compacts were sintered in reducing atmosphere. After full characterization, as-sintered specimens were austenitized and quenched in water. Tempering treatments were also carried out in terms of decreasing the possible brittleness produced during quenching. DSC analysis, dilatometry and thermodynamic calculations together with microstructural characterization were used to set the austenitizing temperatures of the blends. Hardness values from 200 HV10 to 497 HV10 have been achieved together with a dramatic increase in the wear resistance.

Mechanical alloying has been widely utilized to break down the clustered CNTs for incorporation in the metal matrix composites. However, the breakage of CNTs during the ball milling process degrades their effectiveness. Due to the challenges in collecting the CNTs for measurement, quantitative study of CNT breakage has been difficult. In this study, the CNTs with Al6061 powder were mechanically alloyed with high energy milling equipment. The CNTs from the surface of mechanically alloyed particles were collected and measured. Due to the difficulty in obtaining the CNTs embedded inside the particles, a mathematical model has been developed to predict the overall CNT length distribution in the composite. Significant CNT breakage occurred during the initial phase of the mechanical alloying due to the crushing of the clusters. The model predicted that no further change occurred in the overall CNT length during time greater than 1 h of mechanical alloying because most of the CNTs had already become embedded within the particles and were thus protected from further milling media impacts. A faster dispersion of CNTs and lower particle fracturing rate may help preserve the original CNTs.

In this study, the static electrochemical corrosion behavior of nano (SiC)P based aluminum in 3.5% NaCl with and without inhibitor was compared. The metal matrix nanocomposites were produced by using powder metallurgy technique The effect of inhibitor for The metal matrix nanocomposites on the corrosion rate were studied. The corrosion resistance was increased by increasing weight percentage of the nanoparticles, the Al/ 12% nano (SiC)P composites exhibited the highest corrosion resistance among all the evaluated nanocomposites with and without inhibitor. FTIR was used to analysis the film formed on the metal matrix composites. The obtained results signified that the mechanism of adsorption of thiourea molecules on the metal matrix composite surface was by physisorption.

Laser powder bed fusion additive manufacturing is used for demanding applications in industries such as aerospace. However, machine-specific, optimized process conditions and parameters are required to assure consistent part quality. In addition, differences in supplied powder can cause variation in the mechanical properties of the final parts. In this paper, the variability in mechanical properties of 316L stainless steel produced with two different laser powder bed fusion machines from two different powder batches was studied by producing an identical set of tensile and impact toughness test specimens. The samples were subjected to stress-relieving, solution annealing and hot isostatic pressing to assess the effectiveness of standardized heat-treatments in reducing variation in the mechanical properties of the built parts. Porosity, microstructure, tensile properties, and impact toughness of the specimens were measured to study the effect of changing the material, machine, and heat treatment. The maximum differences observed between the studied machine-powder combinations were approximately 7% for tensile properties and approximately 20% for impact toughness. HIP reduced the variability in all other studied properties except elongation. All the specimens fulfil the minimum requirements set in ASTM F3184-16 for AM 316L.

A non-equiatomic AlCoCr0.75Cu0.5FeNi alloy has been identified as a potential high strength alloy, whose microstructure and consequently properties can be widely varied. In this research, the phase structure, hardness, and magnetic properties of AlCoCr0.75Cu0.5FeNi alloy fabricated by laser powder bed fusion (LPBF) are investigated. The results demonstrate that laser power, scanning speed, and volumetric energy density (VED) contribute to different aspects in the formation of microstructure thus introducing alterations in the properties. Despite the different input parameters studied, all the as-built specimens exhibit the body-centered cubic (BCC) phase structure, with the homogeneous elemental distribution at the micron scale. A microhardness of up to 604.6 ± 6.8 HV0.05 is achieved owing to the rapidly solidified microstructure. Soft magnetic behavior is determined in all as-printed samples. The saturation magnetization (Ms) is dependent on the degree of spinodal decomposition, i.e., the higher degree of decomposition into A2 and B2 structure results in a larger Ms. The results introduce the possibility to control the degree of spinodal decomposition and thus the degree of magnetization by altering the input parameters of the LPBF process. The disclosed application potentiality of LPBF could benefit the development of new functional materials.

The sinterability and mechanical properties of different metallic alloys, used as bonds for diamond impregnated tools, have been studied as a function of the processing conditions and the composition of the powder mixtures. The bonds based on Fe-Cu and Fe-Co-Cu prealloyed powders have been consolidated up to full density by free sintering in a reducing atmosphere at temperatures ranging from 750 to 1000 °C. These new alloys present hardness values ranging from 88 to 108 HRB with yield stresses between 600 and 400 MPa and elongations up to 25 %. Calorimetry and the analysis of the sintering atmosphere have been used to understand the densification process of these alloys. Changes in mechanical properties have been related with key microstructural phenomena, i.e. grain growth, phase transformation, precipitation and solid solution strengthening.

Bachelor thesis presenting potential metal powders application as a renewable source of energy. It contains analysis of advantages and disadvantages of 8 different metal fuels such as iron, magnesium, aluminium, beryllium, boron, ferrosilicon, magnalium, titanium-magnesium basing on an internal combustion engine model designed for metal powders.

In this work, Mg and Zn powder were used to prepare the Mg-Zn/β-TCP composites with different β-TCP composition by using powder metallurgy technique. The composite were mixed using ball mill and compacted at 500 MPa. The composites sintered at 450 °C in tube furnace for two hours. The effects of properties on Mg-Zn with different composition of β-TCP were studied. The results on the effect of β-TCP composition were analyzed in terms of density and microstructural analysis.

The development of low-cost Titanium alloys can be tackled by reducing the cost of the raw materials a nd/or reducing processing costs. Material savings can be performed replacing V by additions of other beta-phase stabi lizers as Fe and Cr, while reducing processing costs are possible du e to the use of near-net-shape techniques as Powder Metallurgy. Both aspects have

The present study examines the influence of different contents and types of process control agent (PCA), i.e., stearic acid (SA) and ethylene-bis-stearamide (EBS), on the microstructural evolution and characteristics of Ti-16Sn-4Nb (wt pct) alloy powders and bulk samples. The characterization of the powders and bulk samples was carried out by using chemical analysis, optical microscopy, scanning electron microscopy (SEM) combined with energy-dispersive spectrometry (EDS), and X-ray diffractometry. Results indicated that the powder recovered from the ball milling containers increased with increasing amounts of SA and EBS. Furthermore, adding more SA or EBS to the powder mixture resulted in a considerably smaller particle size, with a flaky-shaped morphology for the given ball milling time. Also, a slightly higher effectiveness was found for EBS when compared to SA. Meanwhile, the addition of both SA and EBS led to a delay in the alloy formation during mechanical alloying (MA) and caused contamination of the material with mainly carbon (C) and oxygen (O). An optimum amount of 1 wt pct PCA led to a good balance between cold welding and fracturing, and thus favored the formation of the titanium alloy. The microstructural observation of the bulk alloy showed a homogeneous distribution of fine Nb-rich β-phase colonies within the α-Ti matrix with the addition of PCA less than 1 wt pct.

A right selection of filler, its type, shape, size, amount and its compatibility with other co-fillers decide the performance of a friction material (FM) at selected operating condition. Amongst various types of metallic fillers, copper is one of the most important fillers used in such multi-ingredient composite system. It not only enhances the thermal conductivity of composite but also plays an important role in friction and wear mechanism. In spite of these facts, in depth systematic studies on investigation role of copper with varying amount and shape and evaluation as per standard procedure are not documented. Hence, in this work investigation on the role of copper (particles and fibers) in FMs were done. Two series of NAO friction composites with varying amount of copper powder and fibers (0, 10 and 20wt.%) were developed in laboratory. These were characterized for physical, thermo-physical, chemical and mechanical properties. For tribo-evaluation inertia brake-dynamometer test...

Le monocarbure de tungstène (WC) est très utilisé dans le domaine de la mécanique, en particulier dans la fabrication des outils de coupe et de forage. Le phénomène de carburation du tungstène nécessite un contrôle strict de la teneur en carbone : le moindre déficit en cet élément favorise la formation de l'hémicarbure W 2 C[1]. Ces deux carbures son appréciés pour leurs grande dureté et tenue à l'usure. Néanmoins, ces deux composés ne sont jamais utilisés comme matériaux de structures en raison de leur grande fragilité. Cependant, ils sont mélangés à des métaux ou alliages qui apportent la ductilité nécessaire. Les matériaux obtenus conjuguent les propriétés de la céramique WC et du métal [2] d'où leur nom de cermet (Céramique-métal). En raison des très hautes températures de fusion des carbures, la métallurgie des poudres reste la technique d'élaboration préférée pour de tels matériaux. Dans ce travail, nous avons utilisé la technique d'infiltration par un alliage de cuivre (bronze au nickel) placé sur une poudre de carbure de tungstène tassée. A la température de 1180°C, l'infiltrant passe à l'état de fusion et s'écoule dans la porosité laissée par les particules solides du carbure de tungstène. L'écoulement du liquide entre les particules est favorisé par la gravité et le phénomène de capillarité qui contribuent à une meilleure densification du matériau. Le matériau obtenu est un composite formé d'une matrice de bronze et de particules dures de carbure WC et W 2 C.

In recent years; additive manufacturing technologies has become widely used in aviation and biomedical sectors as it allows the production of complex parts with less waste materials. Additive manufacturing of titanium alloys; which are currently widely used because of the advantages they provide in these sectors, has been an important research subject. The production of Ti-6Al-4V allloy, which is used in structural parts in the aviation sector and prostheses in the biomedical sector, with additive manufacturing technologies is rapidly increasing. In this study; the usage areas of titanium parts, the production of titanium powders, different additive manufacturing technologies used in the production of titanium parts, comparsion of these technologies with conventional techniques and the effects of post treatments on titanium additive manufactured parts have been investigated.

The abundance of granular materials and powders that are being used in several fields, along with their broad applications, requires a comprehensive understanding of both their macro-and micro-mechanical behavior. The fabric and structural properties, or the inter-particle properties, such as the angle of repose, do affect the behavior of granular materials. This comprehensive review indicates that the angle of repose of granular material is an essential parameter to understand the micro-behavior of the granular material and, then, to relate it with the macro-behavior. Therefore, this extensive review was prepared about the repose angle theory, its definitions, method of measurements, appropriate applications and the influencing factors.

Plastic deformation is an important process to improve and obtain final product for sintered powder materials to compete with solid metal formed parts. The densification behaviour and forming limits of sintered iron–0.35% carbon steel preforms with different aspect ratios, during cold upsetting with two different lubricating constraints namely nil/no and graphite lubricant were investigated experimentally and is presented in this

The monograph presents theoretical approaches and concepts, analytical reviews, practical solutions in specific areas of metallurgy.
The publication may be interesting to Uzbek and foreign scientists, managers and specialists of factories and metallurgical organizations, engineers, technologists, teachers, masters and students of higher educational institutions.
Responsibility for the authenticity and accuracy of citations, names, titles and other information, as well as for compliance with intellectual property laws lies with the authors of published materials.