Features of the Sintering of Fe–Cu–Sn–Ni and Cu–Ti–Sn–Ni Powders during Hot Pressing

Powder Metallurgy and Metal Ceramics - The efficiency and durability of a diamond tool fabricated using powder metallurgy methods depend on several factors. These are the quality of diamond...     

Temperature–Composition Dependence of Thermodynamic Mixing Functions of Co–Cr–Cu–Fe–Ni Melts

Powder Metallurgy and Metal Ceramics - In the framework of the CALPHAD method, a thermodynamic database was developed for calculating the thermodynamic properties of liquid alloys in the...     

Solidification Behaviour of Ti–Cu–Fe–Co–Ni High Entropy Alloys

For the first time, we report here that the development of the novel Ti?CCu?CFe?CCo?CNi high entropy alloys (HEAs) via vacuum arc melting technique using non consumable tungsten electrode under high purity Ar atmosphere on a water-cooled copper hearth. Ti?CCu?CFe?CCo?CNi multicomponent alloys with varying Ti/Cu (x) molar ratio (x?=?1/3, 3/7, 3/5, 9/11, 1, 11/9 and 3/2) have been prepared through the tailoring of microstructure to get understanding of the phase formation and the microstructural evolution of these multicomponent HEAs. X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopic results confirm the presence of (Cu)_ss, (Co)_ss and (??-Ti)_ss dendrites with ultrafine eutectic between cubic (Cu)_ss and Laves phase (Ti₂Co type). The solidification pathways of novel alloys are critically discussed as follows. For x?=?9/11, 1, 11/9 and 3/2; firstly, (??-Ti)_ss dendrite is formed from the liquid, followed by the liquid phase separation between the cobalt-rich solid solution (Co)_ss and copper-rich solid solution (Cu)_ss and finally, the remaining liquid undergoes eutectic reaction between copper solid solution (Cu)_ss and the Laves phase (Ti₂Co Type), whereas for x?=?1/3, 3/7 and 3/5; (??-Ti)_ss dendrite is formed first from the liquid and then remaining liquid undergoes the liquid phase separation resulting two different dendrites of (Cu)_ss and (Co)_ss phases. Detailed thermodynamic calculations have been carried to rationalize the formation of stable solid solution phases of these newly developed multicomponent Ti?CCu?CFe?CCo?CNi HEAs.     

Effect of gadolinium on the properties of Pr–Dy–Fe–Co–B materials

Sintered (Pr_1–x–y Dy _x Gd _y )_13–14(Fe_1–z Co _z )_balB_6–7 materials (x = 0.18–0.58, y = 0.05–0.33, z = 0.2–0.36) have been studied. The magnetic moments of gadolinium ions and those of the sublattice formed by Fe and Co ions are shown to be ordered antiferromagnetically. It is noted that an increase in the content of gadolinium, which substitutes for dysprosium, leads to an increase in residual induction B _r , a decrease in coercive force H _cJ , and an increase in the absolute value of the temperature coefficient of induction. The opposite effect takes place in the case of substitution of gadolinium for praseodymium in materials with a fixed dysprosium content.     

粉末锻造Fe–Ni–Cu–C–Mo齿轮材料热处理及性能研究

对Fe–Ni–Cu–C–Mo粉末锻造材料的锻后热处理工艺进行了研究,通过动态连续冷却转变试验绘制出该材料的连续冷却转变（continuous cooling transformation,CCT）曲线,指导材料锻后冷却工艺的选取。对Fe–Ni–Cu–C–Mo淬火试样进行不同温度的低温回火试验,探究不同回火温度对该材料微观组织与力学性能的影响。结果表明,当锻后冷却速率大于7.0 ℃·s?1时,Fe–Ni–Cu–C–Mo粉锻材料组织全为马氏体,硬度趋于稳定;在150 ℃和175 ℃回火,碳化物均匀地分布在马氏体板条内部,起到析出强化的作用,材料表现出优异的抗拉性能。     

Solid-State Reactions of SiC–TiO2–MgO System and Phase Relations in SiC–SiO2–TiC–TiO2–MgO System

Powder Metallurgy and Metal Ceramics - Preliminary experiments revealed solid-state reactions in the SiC–TiO2–MgO system that resulted in forming TiC compound, providing, thus, a new...     

Sintering Behaviour and Mechanical Properties of Al–Cu–Mg–Si–Sn Aluminum Alloy

The present study investigates the effect of compaction pressure and sintering temperature on densification response and mechanical properties of the Al–3.8Cu–1Mg–0.8Si–0.3Sn (2712) alloy. The compacts were pressed at 200 and 400 MPa and sintered at temperatures ranging from 570–630°C in vacuum (10^?6 Torr). The objective of the present work is to obtain an optimum sintering conditions for achieving higher sintered densities and mechanical properties. The effect of sintering temperature is evaluated by measuring the sintered density, densification parameter, microstructure, phase changes and mechanical properties. While a higher sintering temperature results in densification enhancement, it also leads to microstructural coarsening. Significant improvement in mechanical properties is obtained through age-hardening of sintered alloy under various ageing conditions (T4, T6 and T8).     

Processability and Structure Formation of the Al–Zn–Mg–Ca–Fe–Zr–Sc Alloy upon Hot Rolling and TIG Welding

Russian Journal of Non-Ferrous Metals - Technological regimes for producing wrought products (2 and 1 mm) from the Al–4.5%Zn–2.5%Mg–2.5%Ca–0.5%Fe–0.2%Zr–0.1%Sc...     

Iron–Chromium Precursors for Hard-Magnetic Fe–Cr–Co Alloys

The effect of the chromium concentration on the magnetic properties of Fe–Cr precursors for hard-magnetic Fe–Cr–Co materials is studied. Nitrogen used as a sintering atmosphere and a long annealing time enhance are found to increase the coercive force H_c of the materials. The phase formation in Fe–30% Cr alloys is traced during heat treatment in nitrogen and argon atmosphere using thermal analysis.     

Calcium hydride reduced high-quality Nd–Fe–B powder from Nd–Fe–B sintered magnet sludge

The structural and magnetic properties were studied for recycling Nd–Fe–B powders from Nd–Fe–B sintered magnets sludge via reduction diffusion (RD) with calcium hydride (CaH₂) particles. For comparison, traditional reducing agent calcium granules were applied to prepare recycled Nd–Fe–B powders. Finer particle size and better size distribution as well as lower impurity content are achieved by using CaH₂ instead of Ca. In detail, the average particle size of the recycled Nd–Fe–B powder is reduced from 4.66 to 3.43 μm, and the bimodal distribution disappears. Moreover, the residual calcium content and oxygen content are reduced to about 0.080 wt% and 0.32 wt%. As a consequence, the room-temperature magnetization of the CaH₂-recycled Nd–Fe–B powder is increased to 146.30 emu/g, 6.8% and 33%, respectively, higher than that of Ca-reduced powder and the initial sludge. Further analysis indicates that CaH₂ is able to reduce the sludge at lower temperature to fabricate well-dispersed, uniform recycled powder with high magnetization arising from a combination factors of its low melting point, low thermodynamic behavior, and the release of hydrogen during the reaction.     

Fine Grained WC–VC–Co Hardmetal

Abstract

Preliminary work on the preparation process and some properties of VC–WC–Co alloys containing approximately 10 wt–%VC and 10 wt–%Co are reported. Sinterability of the alloys proved to be better than expected and hardness higher than the hardness of WC–Co alloys of equal cobalt content. The toughness was found to be superior to that of WC–Co alloys of equal hardness. PM/0742     

Structure of Fe–Nb–Cu–Si–B Nanocrystalline Alloy Strip Produced by Melt Spinning

Recently, amorphous and nanocrystalline magnetically soft iron alloys have been used to create protective materials that are effective in a broad range of magnetic and electromagnetic fields. These alloys are obtained in strip form by superfast quenching of a plane melt jet on a rapidly spinning cooled disk. In the production of amorphous strip, metal melted in a high-frequency inductor is supplied through a cut on the surface of the cooling disk. The surface layers of the congealing strip in contact with the cooled disk are cooled more rapidly than higher layers in no contact with the disk. As a result, residual compressive stress may be formed on the contact side of the strip, while tensile stress may be formed on the free side. This may lead to anisotropic structure and properties over the strip thickness. In the present work, the structure is investigated by transmission microscopy (planar geometry and cross-sectional geometry) over the thickness of AMAG-200 Fe–Nb–Cu–Si–B alloy strip obtained by spinning. A relation is established between AMAG-200 Fe–Nb–Cu–Si–B alloy strip produced in controlled crystallization and the structure of the amorphous strip obtained by superfast quenching of melt at rates up to 10⁶ K/s. That explains the structural anisotropy over the strip thickness. Heat treatment at 530°C forms excellent magnetic characteristics and decreases the work of destruction on account of the formation of optimal amorphous–nanocrystalline structure in terms of the bulk content and size of the crystallites. A scanning electron microscope is used to study the destruction of strip associated with the structure formed in the strip on superfast quenching from melt and after heat treatment at 530°C. In the state supplied, the surface fracture of the strip on sudden decrease in grain size is ductile; after heat treatment, it is consistently brittle.     

Structure and Mechanical Properties of Al–Ca–Mn–Fe–Zr–Sc Eutectic Aluminum Alloy after Warm Equal Channel Angular Pressing

Russian Journal of Non-Ferrous Metals - Recently developed multicomponent eutectic alloys based on Al–Ca are promising for practical application, since they are characterized by low density...     

Research on Nitrogen Solubility of Fe–Cr–Mn–V–N System Alloys in Liquid and Solid Phases

In this paper, the thermodynamic model of nitrogen solubility in vanadium nitrogen microalloyed high strength weathering steels of Fe–Cr–Mn–V–N system, according to Hillert’s model for Gibbs energy of its various phases, was established and validated. In the model, the effect of the nitrogen partial pressure on the activity coefficient and the lattice structure characteristics of the vanadium nitrogen precipitated phase were considered. It would be of guiding significance for the design and smelting of Fe–Cr–Mn–V–N system alloys. Based on the established model, the nitrogen contents in \(\delta\), \(\gamma\), \(\alpha\) phase and liquid were calculated as a function of the temperature for Fe–Cr–Mn–V–N system alloys. The results show that: first, the maximum solubility of nitrogen in the solidification process is obviously affected by the phase transition when there is a sudden change in the solubility of nitrogen at the phase transition point. The maximum nitrogen solubility of the molten steel in the delta phase region determines whether nitrogen bubbles are formed during the solidification process. The nitrogen solubility is lowest in the solid–liquid region (about 1673 K). Secondly, the increase of Cr and Mn content is beneficial to improve nitrogen solubility in liquid and solid phases. However, the increase of V content mainly affects the nitrogen solubility in the solid phase because the nitrogen in this temperature range is precipitated in the form of vanadium nitride, as the second phase plays a role in strengthening. In addition, the alloying element Mn has a significant effect on nitrogen solubility since the Mn element is the promoting element of austenitic formation. During the solidification process, the delta ferrite region gradually reduces and may disappear with increasing Mn content. Therefore, increasing the Mn content of the alloy system in the design of alloy composition, can reduce the precipitation trend of the nitrogen during the solidification process, which can effectively avoid bubble formation in high nitrogen weathering steels. Lastly, with the increase in the nitrogen partial pressure, the solubility of nitrogen increases during the liquid and solid phases.     

粉末冶金法制备Ta–W–Si合金

采用热压烧结和放电等离子烧结的方法制备了Ta–W–Si合金,利用X射线衍射分析、扫描电子显微镜观察、背散射电子成像及能谱分析等手段研究了合金的显微结构和相组成,并讨论了烧结方式和硅质量分数对合金烧结致密化和硬度的影响。结果表明,两种烧结方式烧结后的样品相对密度均达到了96%以上,可以实现致密化,硅元素的添加有利于合金的致密化;扫描电子显微观察和背散射电子成像显示合金中出现两种不同区域,物相分析存在Ta–W与Ta_3Si两相;硅元素的添加有利于提高合金硬度,硅化物第二相强化、细晶强化和晶界区的氧化富集是强化的主要机制。     

Effect of cobalt on the oxidation resistance of Pr(Nd)–Dy–Fe–Co–B materials

The effect of cobalt on the oxidation resistance of (Nd_0.85Dy_0.15)_16.4(Fe_0.89Co_0.11)_74.4Ti_1.3B_7.9 and (Pr_0.56Dy_0.39Sm_0.05)_14.5(Fe_0.75Co_0.25)_78.8B_6.7 alloys has been studied. The storage of magnet blanks made from these alloy in air for 200 h does not affect the magnetic properties of the sintered magnets owing to the presence of the phases (Pr, Dy)(Fe, Co)₂, (Pr, Dy)(Fe, Co)₂B₂, (Pr, Dy)(Fe, Co)₄B, (Pr, Dy)(Fe, Co)₃B₂, and (Pr, Dy)(Fe, Co)₃, which are resistant to oxidation and ensure liquid-phase sintering of magnets. After 200-h exposure to air, oxidation of the blanks takes place, the rate of which decreases by more than two times at the expense of an increase in the cobalt content in the alloy.     

Production of Al–Cu and Al–Cu–Si Alloys by PM Methods

Abstract

The possibilities of the production of aluminium-base copper and/or silicon alloys by conventional powder compaction and sintering methods have been studied. The effects of various lubricants, pressing, and sintering conditions on the behaviour of Al–Cu and Al–Cu–Si alloys were evaluated systematically. The role of copper and silicon additions during compaction and sintering and their advantages or disadvantages are discussed. All alloys underwent large dimensional changes (sudden swelling followed by rapid contraction) during sintering at temperatures greater than Al–Cu eutectic temperature and it is suggested that a process of particle rearrangement is largely responsible for this behaviour. The mechanical properties of the alloys were highly dependent on the sintering temperature. PM/0215     

Density of Na3AlF6–AlF3–LiF–MgF2–Al2O3–Sm2O3 molten salt melt for Al–Sm alloy

Samarium (Sm) has been widely used in making aluminum (Al)–Sm magnet alloy materials. The research team for this study developed a molten salt electrolyte system which directly produces Al–Sm alloy to replace the energy intensive conventional distillation technology. In this study, molten melt density was measured and operation conditions were optimized to separate Al–Sm alloy product from the fluoride molten melt electrolysis media based on density differences. Archimedes' principle was applied to measure density for the basic molten fluoride system (BMFS: Na₃AlF₆–AlF₃–LiF–MgF₂) electrolysis media in the temperature range from 905 to 1055 °C. The impact of temperature (t) and the Al₂O₃ and Sm₂O₃ addition ratio (w_(Al2O3), w_(Sm2O3)) in the basic fluoride system on molten melt density was examined. The fluoride molten melt density relationship was determined to be: ρ = 3.11701 ? 0.00802w_(Al2O3) + 0.027825w_(Sm2O3) ? 0.00117t. The test results showed that molten density decreases with increase in temperature and Al₂O₃ addition ratio, and increases with the addition of Sm₂O₃, and/or Al₂O₃ + Sm₂O_3. The separation of Al–Sm (density 2.3 g/cm³) product melt from the BMFS melt is achieved by controlling the BMFS density to less than 2.0 g/cm³. It is concluded that the optimal operation conditions to control the BMFS molten salt density to less than 2.0 g/cm³ are: maintain addition of Al₂O₃ + Sm₂O₃ (w_(Al2O3) + w_(Sm2O3)) < 9% of Na₃AlF₆, Al₂O₃/Sm₂O₃ ratio (w_(Al2O3):w_(Sm2O3)) > 7:3, and temperature between 965 and 995 °C.