Nanostructured Ti Consolidated via Spark Plasma Sintering

Cryomilled nanocrystalline commercially pure (CP)-Ti powders were spark plasma sintered (SPS) using different process parameters (heating rate, temperature, pressure, and dwell time) to study densification, microstructure, and mechanical behavior. The results were rationalized on the basis of the relevant literature and experimental results, and they reveal a strong dependence on SPS parameters. An interesting finding was that the measured high ductility was accompanied by a moderate strength (yield strength [YS] = 770 MPa, ultimate tensile strength [UTS] = 840 MPa with ~27 pct elongation to failure). The combinations of microstructure and mechanical response were attributed to the multistep processing at different temperature ranges as well as to the presence of interstitial solutes.     

Spark Plasma Sintering of Cryomilled Nanocrystalline Al Alloy - Part I: Microstructure Evolution

Aluminum alloys are widely used because they are lightweight and exhibit high strength. In recent years, spark plasma sintering (SPS) technology has emerged as a viable approach to sinter materials due to its application of rapid heating and high pressure. In this study, SPS was chosen to consolidate dense ultrafine-grained (UFG) bulk samples using cryomilled nanostructured Al 5083 alloy (Al-4.5Mg-0.57Mn-0.25Fe, wt pct) powder. Both bimodal microstructure and banded structure were observed through transmission electron microscopy (TEM) investigation. The evolution of such microstructures can be attributed to the starting powder and the process conditions, which are associated with the thermal, electrical, and pressure fields present during SPS. A finite element method (FEM) was also applied to investigate distributions in temperature, current, and stress between metallic powder particles. The FEM results reveal that the localized heating, deformation, and thermal activation occurring at interparticle regions are associated with the formation of the special microstructure.     

SiCp/Cu复合材料的SPS烧结及组织性能

以化学镀Cu包覆SiC粉末和高压氢还原法制备的Ni包SiC复合粉末为原料,用放电等离子体烧结法制备了SiCp/Cu复合材料.分析了增强相含量和烧结温度对致密化的影响,比较了非包覆粉末和包覆粉末制备的复合材料的界面结合状况.然后对SiCp/Cu复合材料的热膨胀行为和力学性能进行了研究.结果表明:包覆粉末能够促进材料的致密化并且能获得良好的界面结合,所得SiCp/Cu复合材料的致密度达96.7%,抗压强度达1061 MPa.SiCp/Cu复合材料的热膨胀系数介于7.5×10-6～11.4×10-6·K-1之间,并且随SiC体积分数的增加而降低.材料在热循环过程中出现热滞现象,热滞现象受增强相的含量及界面结合状况的影响.     

W-Re高比重合金的SPS烧结

采用放电等离子烧结(SPS)设备制备了W-Re高比重合金,烧结温度为1800℃,烧结压力为40MPa,保温时间为5min。对SPS烧结的W-Re合金试样进行了密度、硬度等性能测试。采用金相显微镜观察试样的金相组织、晶粒大小。结果表明:采用SPS烧结,可以在较低的温度下实现W-Re合金的致密化,并能有效控制晶粒长大,提高材料的硬度。     

Spark Plasma Sintering of Magnesium Fluoride Nanopowders

Powder Metallurgy and Metal Ceramics - The densification behavior of nanostructured MgF2 ceramics in the spark plasma sintering process is studied. Nitrate synthesis is employed to produce fine...     

放电等离子烧结技术的发展和应用

放电等离子烧结（SPS）是一种快速，低温，节能，环保的材料制备新技术，本文综述了SPS在国内外的发展和应用，介绍了SPS的原理，特点及在新材料制备加工中的应用。     

Influence of Particle Size on Apparent Diffusivity During Spark Plasma Sintering of Crystalline Powders

Metallurgical and Materials Transactions B - A theoretical framework is presented to determine an apparent diffusivity D during powder sintering and further elucidate the underlying interrelation...     

Microstructure Evolution in Nano-reinforced Ferritic Steel Processed By Mechanical Alloying and Spark Plasma Sintering

Oxide-dispersion strengthened ferritic steel was produced by high-energy attrition, leading to a complex nanostructure with deformed ferritic grains. After mechanical alloying, the powder was then consolidated by spark plasma sintering (SPS) using various thermo-mechanical treatments. Hot isostatic pressing (HIP) was also performed on the same powder for comparison. Above 1123 K (850 °C), SPS consolidation-induced heterogeneous microstructure composed of ultra-fine-grained regions surrounded by larger grains. Spatial distribution of the stored energy was measured in the bimodal microstructure using the Kernel average misorientation. In contrary to large recrystallized grains, ultra-fine grains are still substructured with low-angle grain boundaries. The precipitation kinetics of the nano-oxides during consolidation was determined by small-angle neutron scattering. Precipitation mainly occurred during the heating stage, leading to a high density of nanoclusters that are of prime importance for the mechanical properties. Other coarser titanium-enriched oxides were also detected. The multiscale characterization allowed us to understand and model the evolution of the complex microstructure. An analytical evaluation of the contributing mechanisms explains the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Then, the thermal stability of coherent nano-oxides is responsible for effective grain boundary pinning in recovered regions where the driving pressure for recrystallization is lowered. This scenario is confirmed in both SPSed and HIPed materials.     

Pressureless Spark Plasma Sintering: A Perspective from Conventional Sintering to Accelerated Sintering Without Pressure

Powder Metallurgy and Metal Ceramics - Spark plasma sintering (SPS) has been an attractive technique for many researchers seeking to consolidate metals and ceramics. This technique’s high...     

放电等离子烧结TbFeCo磁光靶材工艺研究

研究了采用放电等离子烧结技术制备TbFeCo磁光靶材的工艺过程，考察了烧结温度对材料组织均匀性和致密度的影响。利用扫描电子显微镜和能谱分析仪对材料的微观组织形貌及成分进行了分析，同时用阿基米德法测量了材料的密度。结果表明：适当的提高烧结温度可以使材料得到均匀的组织，理想的致密度。但过高的烧结温度会造成材料局部组织的熔化，使材料的组织均匀性变差，l010℃的烧结温度是制备具有均匀组织和理想致密度Tb(Fe，Co)3材料的最佳温度。     

Spark Plasma Sintering Bulk Sm2 Fe17NxMagnets

High performance Sm2Fe17Nx magnetic powders were fabricated by ball-milling method and were compacted using spark plasma sintering(SPS) technique.Effects of processing conditions on the magnetic properties and decomposition dynamic of the magnets were investigated.It is found that higher sintering temperature improves the densification of the magnets, while deteriorates their magnetic properties simultaneously due to the decomposition of the Sm2Fe17Nx.Sintering at lower temperature can preserve the crystal structure of Sm2Fe17Nx compound, while the powders cannot be consolidated into a fully dense compact.An increased compressive pressure leads to better magnetic properties and higher density for the magnet at the same sintering temperature.     

Microstructure,Mechanical Properties,and Sliding Wear Behavior of Oxide-Dispersion-Strengthened FeMnNi Alloy Fabricated by Spark Plasma Sintering

Metallurgical and Materials Transactions A - The face-centered-cubic (fcc) CoCrFeMnNi high-entropy alloy suffers from low strength and wear resistance at ambient temperature. Herein, we developed a...     

Study of Molybdenum-Tungsten Powder Compaction Processes by Spark Plasma Sintering

Metallurgist - This paper presents the results of studying the production of molybdenum-tungsten alloys by spark plasma sintering at various process conditions, as well as the processes of material...     

Spark Plasma Sintering of Cryomilled Nanocrystalline Al Alloy - Part II: Influence of Processing Conditions on Densification and Properties

In this study, nanostructured Al 5083 powders, which were prepared via cryomilling, were consolidated using spark plasma sintering (SPS). The influence of processing conditions, e.g., the loading mode, starting microstructure (i.e., atomized vs cryomilled powders), sintering pressure, sintering temperature, and powder particle size on the consolidation response and associated mechanical properties were studied. Additionally, the mechanisms that govern densification during SPS were discussed also. The results reported herein suggest that the morphology and microstructure of the cryomilled powder resulted in an enhanced densification rate compared with that of atomized powder. The pressure-loading mode had a significant effect on the mechanical properties of the samples consolidated by SPS. The consolidated compact revealed differences in mechanical response when tested along the SPS loading axis and radial directions. Higher sintering pressures improved both the strength and ductility of the samples. The influence of grain size on diffusion was considered on the basis of available diffusion equations, and the results show that densification was attributed primarily to a plastic flow mechanism during the loading pressure period. Once the final pressure was applied, power law creep became the dominant densification mechanism. Higher sintering temperature improved the ductility of the consolidated compact at the expense of strength, whereas samples sintered at lower temperature exhibited brittle behavior. Finally, densification rate was found to be inversely proportional to the particle size.     

Spark Plasma Sintering Nd-Fe-B Permanent Magnets With Good All-Around Property

In present study, sintered Nd-Fe-B permanent magnets with different compositions were fabricated by using both Spark Plasma Sintering (SPS) technique and conventional sintering technique. Microstructure and compositions of both magnets are observed by scanning electron microscope with energy dispersive X-ray detector. Magnetic properties, mechanical properties, and chemical stabilities of both Nd-Fe-B magnets are investigated. Compared with the conventional sintered magnets, SPS Nd-Fe-B magnets possess comparable magnetic properties, better corrosion resistance and mechanical properties. Further investigation shows that the good all-around properties of the SPS magnets result from their unique microstructure. In detail, the grain size of Nd₂Fe₁₄B main phase is fine and uniform, only a few Nd-rich phase forms along the grain boundaries of Nd₂Fe₁₄B, while most of them agglomerates into the triple junctions. As a result, SPS process is expected to be a promising method for the production of new Nd-Fe-B magnets with good all-around properties.