Structure,Mechanical Properties,and Corrosion Resistance of the CrCuFeNiMo0.3 High-Entropy Alloy Prepared by Powder Metallurgy

Powder Metallurgy and Metal Ceramics - Powder metallurgy methods were used in this study to prepare the CrCuFeNiMo0.3 high-entropy alloy. The alloy’s microstructure, hardness, compression,...     

MHC合金粉末冶金制备及其锻造棒材力学性能研究

针对MHC合金粉末的冶金制备工艺及其烧结坯性能、锻造态和经热处理后的MHC合金棒组织与力学性能开展研究。结果表明:所研究的粉末冶金工艺参数可制备出适宜于锻造加工的MHC烧结棒坯;相比于烧结坯,经88.6%锻造比锻造后MHC合金棒材的硬度、强度显著提高;经88.6%锻造比锻造后的MHC合金棒材的完全再结晶温度高于1500℃,经1200℃保温1 h热处理后,MHC合金棒材的室温强度Rp 0.2>770 MPa,硬度达到HRA 66.5;真空气氛下800℃高温拉伸强度Rp 0.2>450 MPa,延伸率大于18.5%。表明本研究制备的MHC合金棒材具备显著的室温高强高硬特性和良好的高温综合力学性能。     

真空脱气对粉末冶金Ti2AlNb合金力学性能的影响

采用无坩埚感应熔炼超声气体雾化法制备了成分为Ti-22Al-24Nb-0. 5Mo(原子分数,x/%)的预合金粉末,并对预合金粉末的化学成分、表面状态及流动性等进行了表征。通过包套热等静压工艺制备了粉末冶金Ti2AlNb合金,研究了真空脱气对粉末冶金Ti2AlNb合金力学性能的影响。结果表明,超声气体雾化法制备的Ti2AlNb合金粉末化学成分批次稳定性好;从粉末填充的工艺性能方面考虑,热等静压成形应选取粒度小于250μm以下的全粒度分布预合金粉末;真空脱气处理可减少粉末冶金Ti2AlNb合金的孔隙缺陷,提升合金拉伸性能的稳定性和高温持久寿命。     

Preparation and Properties of Magnetically Soft Powder Metallurgy Alloy 79NM

The effect of production conditions and heat treatment on the magnetic properties and structure of powder metallurgy soft magnetic alloy 79NM were investigated. Optimal structure and magnetic properties were attained after heat treatment in hydrogen at 1150°C and a final heat treatment at 1300°C for maximum time.     

TA7ELI粉末冶金材料力学性能与显微组织

以TA7 ELI钛合金棒为原料,用等离子旋转电极工艺制备出高品质钛合金球形粉末.采用热等静压成形工艺,将粉末压制成钛合金材料,并研究了材料的组织和力学性能.结果表明:等离子旋转电极工艺制备的钛合金球形粉末具有非常高的球形度和振实密度,粒度分布比较窄,非金属夹杂含量非常低;热等静压制备的低温钛合金达到全致密,其组织均匀细...     

Mechanical Properties and Microstructure of Argon Atomized Aluminum-Lithium Powder Metallurgy Alloys

Aluminum-lithium and aluminum-copper-lithium alloy powders were prepared by argon gas atomization. The powders were consolidated by hot pressing and extruded into flat bar. Tensile and impact properties were determined on the extrusions. Transmission electron microscopy was used to examine the extruded microstructures while scanning microscopy was used for the examination of fracture surfaces. The aluminum-lithium alloys showed higher moduli, lower densities, and reduced toughness and elongation compared to conventional aluminum alloys. The loss of toughness was particularly pronounced above 3 pct Li.     

Mechanical Properties of TiTaHfNbZr High-Entropy Alloy Coatings Deposited on NiTi Shape Memory Alloy Substrates

TiTaHfNbZr high-entropy alloy (HEA) thin films with thicknesses of about 750 and 1500 nm were deposited on NiTi substrates by RF magnetron sputtering using TiTaHfNbZr equimolar targets. The thorough experimental analysis on microstructure and mechanical properties of deposited films revealed that the TiTaHfNbZr films exhibited amorphous and cauliflower-like structure, where grain size and surface roughness increased concomitant with film thickness. More importantly, the current findings demonstrate that the TiTaHfNbZr HEA films with mechanical properties of the same order as those of the NiTi substrate constitute promising biomedical coatings effective in preventing Ni release.     

Composite Ferrous Powder Metallurgy Structures: Mechanical Properties and Stress Analysis

Macrocomposite mechanics modeling is done for asymmetrical triplex structures. Relative parameters are obtained for the location of the centroid and the moment of inertia of triplex structures. The general analysis described can be applied to the special cases of symmetrical sandwich and asymmetrical duplex structures. The stress analysis includes the effect of the residual stress, and residual stress factors are determined for the special case of asymmetricaduplex structures. The rule-of-mixtures yield strength calculation with use of the relative parameters and residual stress factors was found to correlate very well with experimental results for macrocomposite ferrous powder metallurgy (P/M) duplex, 4620 and 4660, structures. The effects of volume fraction and the variations of elastic moduli of the constituents are examined. formerly with Drexel University formerly with Drexel University, Philadelphia, PA     

粉末冶金TiAl基合金及其力学性能的研究进展

综述了粉末冶金法制备TiAl基合金的几种方法，包括预合金粉末法、元素粉末法、自蔓延高温合成、放电等离子烧结等方法，介绍了采用粉末冶金方法制备TiAl基合金的力学性能的研究，指出当前粉末冶金TiAl基合金制备中存在的问题及研究重点。     

Mechanical Properties of Aluminium-Graphene Composite Synthesized by Powder Metallurgy and Hot Extrusion

The present work focuses on the development of multilayer graphene reinforced aluminium metal matrix composites by powder metallurgy followed by hot extrusion. Microstructure, grain size analysis and mechanical properties of hot extruded unreinforced aluminium and graphene reinforced aluminium composites are presented here. Microstructure shows uniform distribution of graphene throughout the matrix. Experimental results reveal significant increase in hardness as well as tensile strength of composite as compared to unreinforced aluminium. The improvements in properties are attributed to uniformly dispersed graphene sheets, an excellent interfacial bonding between graphene and aluminium matrix and grain refinement caused by the addition of graphene. Further, the strengthening mechanisms involved in the aluminum-graphene composite have been discussed. The fracture studies show the transition of ductile fracture in case of pure aluminium to brittle fracture in case of aluminium-graphene composites.     

Influence of Annealing on Microstructure and Mechanical Properties of Refractory CoCrMoNbTi0.4 High-Entropy Alloy

Metallurgical and Materials Transactions A - A novel refractory CoCrMoNbTi0.4 high-entropy alloy (HEA) was prepared via vacuum arc melting. After annealing treatment at different temperatures, the...     

Microstructure and Mechanical Behavior of Powder Metallurgy Mg98.5Gd1Zn0.5 Alloy

The Mg_98.5Gd₁Zn_0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg₃Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.     

Overcoming the Strength-Plasticity Trade-Off in a Multi-phase Equiatomic CrCuNiTiV 3d Transition Metal High-Entropy Alloy

The phase components, microstructures, and mechanical properties of a multi-phase equiatomic 3d transition metal high entropy alloy, CrCuNiTiV, were investigated. In the as-cast condition, the alloy was mainly composed of a body-centered cubic (BCC) dendritic phase and a face-centered cubic (FCC) interdendritic phase, with the BCC dendrite uniformly distributed in the FCC matrix. Through annealing, three phases decomposed from the FCC parent phase, and small particles and stripes were derived from the elongated stripes of the as-cast alloy. Outstanding plasticity was acquired with only a small sacrifice in the yield strength after annealing. Specifically, the plasticity increased from 12.7 pct in the as-cast condition to 23.4 pct in the annealed condition while high yield strengths of 965 and 877 MPa were retained in the as-cast and annealed alloys, respectively. Overcoming the strength-plasticity trade-off in the annealed CrCuNiTiV alloy was mainly achieved via the large volume fraction of FCC interdendritic phases, together with the precipitation of one BCC phase and two FCC phases.

     

Properties of a Tool Produced by Powder Metallurgy

To minimize the manufacturing costs of parts with specified operational properties, the machining processes must be optimized. Cutting accounts for at least 70% of such processes. To that end, tool materials with distinctive properties may be developed and utilized. Analysis of manufacturing components—in particular, power components in gas-turbine engines—shows the need for higher quality of the machined surfaces and more efficient use of expensive equipment with numerical and adaptive control systems, so as to ensure a wide range of cutting conditions, including high-speed cutting. To obtain products that are domestically and internationally competitive, we need to optimize cutting processes, in which the tool is the weakest link in the technological chain. Defects of the cutting tool impair the productivity and product quality. In the present work, the wear of cutting tools produced by the sintering of high-speed steel powder is studied. Tool materials based on high-speed steel with additional alloying by titanium carbide (carbide steel) are shown to be highly wear-resistant. They may be classified as a new category of self-organizing tool materials. The results indicate the expediency of additional alloying by two methods to modify the tool friction and wear: (1) alloying with compounds that considerably reduce the self-organization by decreasing the frictional coefficient at working temperatures; (2) alloying to expand the range of self-organization. Both methods result in lower frictional forces and temperatures, as confirmed by the change in wear resistance and frictional characteristics. The wear resistance of such tools is found to be 2–3.5 times that of regular high-speed steel tools.     

Evaluation of Thermal and Mechanical Behavior of CuNiCoZnAl High-Entropy Alloy Fabricated Using Mechanical Alloying and Spark Plasma Sintering

Thermal behavior investigation of CuNiCoZnAl high-entropy alloy powder produced by mechanical alloying indicated that a FCC single-phase solid solution transformed into two new phases at 500 °C. Despite this phase transformation, no indication of intermetallic compounds or amorphous phases was detected. Heat treatment of the high-entropy alloy was then carried out for 2 hours, and the nanocrystalline structure of heat-treated milled powder was retained up to 1000 °C. Besides, grain growth of CuNiCoZnAl high-entropy alloy powder at high homologous temperatures (> 0.6 T_m) was studied, and sluggish grain growth of the powder was observed clearly. Consolidation of the alloy powder was performed by spark plasma sintering at 800 °C, and a sample with porosity of 6.87 pct and density of 7.32 g cm⁻³ was achieved. Elastic moduli, Vickers microhardness, and fracture toughness of the bulk sample were measured as 186 ± 17 GPa, 599 ± 31 HV, and 4.45 MPa m^0.5, respectively. The evaluation of wear behavior indicated that the dominant wear mechanism was adhesive wear. Moreover, tribochemical wear (oxidation) was found to be the minor wear mechanism. The present study revealed that CuNiCoZnAl high-entropy alloy has the potential to be used in many applications that high hardness and low elastic moduli are favorable.

     

时效处理对Al0.5CoCrFeNi高熵合金微观组织结构和力学性能的影响

对Al0.5CoCrFeNi高熵合金经不同温度时效处理24 h后的微观组织和力学性能进行研究。结果表明:时效处理前后,Al0.5CoCrFeNi高熵合金均由简单的体心立方相和面心立方相组成,组织主要为树枝晶形貌。但是,随着时效温度的升高(800℃和1 000℃),树枝晶析出弥散分布的针状第二相,且第二相数量不断增大。由于第二相的弥散强化作用,时效处理能显著提高合金的抗拉强度。     

Magnetic Properties of FeSiBC Amorphous Alloy Powder Cores Using Mechanical-crushed Powder

The FeSiBC amorphous powder cores were fabricated using powders of the FeSiBC amorphous ribbons which were mechanically crushed for a short time, and the relationship between magnetic properties and powder particle sizes was evaluated. The saturation magnetization Bs of the amorphous Fe82Si2B15C1 alloy was 1.62 T, which provided a superior dc-bias property for the powder cores. Meanwhile, a stable permeability up to high frequency range over 10 MHz and the low core loss of 400 kW/ma at f=50 kHz and Bm =0.1 T were obtained. These excellent high-frequency magnetic properties of the FeSiBC amorphous powder cores could be attributed to the effective electrical insulation between the FeSiBC amorphous powders made by mechanical crushing.     

Titanium Foams Processed Through Powder Metallurgy Route Using Lubricant Acrawax as Space Holder Material

In the present work titanium foams have been synthesized using acrawax as the space holder material. Acrawax has generally been used as a lubricant for easier compaction of aluminium alloy powders. This study deals with the use of this space holder material in the form of beads for creating pores in titanium metal matrix. Acrawax facilitates the formation of continuous dense cell walls which is difficult to obtain using ordinary space holder materials. Moreover, acrawax is compressible in nature and it facilitates the formation of better and uniformly sized pores. Titanium foams have been synthesized utilizing acrawax in two different sizes. The effect of using differently sized acrawax on the cell walls and mechanical properties has also been carried out in this study.