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.     

High-Temperature Tensile Properties of Nano-Oxide Dispersion Strengthened Ferritic Steels Produced by Mechanical Alloying and Spark Plasma Sintering

Oxide-dispersion strengthened (ODS) ferritic steels were produced by mechanical alloying and subsequent spark plasma sintering. Very fast heating rates were used to minimize porosity when controlling grain size and precipitation of dispersoids within a compacted material. Sintering cycles performed at 1373 K (1100 °C) induced heterogeneous, but fine grain size distribution and high density of nano-oxides. Yield strengths at room temperature and at 923 K (650 °C) are 975 MPa and 298 MPa, respectively. Furthermore, high-temperature ductility is much increased: total strain of 28 pct at 923 K (650 °C).     

Mechanical Behavior of Al-SiC Nanocomposites Produced by Ball Milling and Spark Plasma Sintering

Al-SiC nanocomposites were prepared by high energy ball milling of mixtures of pure Al and 50-nm-diameter SiC nanoparticles, followed by spark plasma sintering. The final composites had grains of approximately 100 nm dimensions, with SiC particles located mostly at grain boundaries. The samples were tested in uniaxial compression by nano- and microindentation in order to establish the effect of the SiC volume fraction, stearic acid addition to the powder, and the milling time on the mechanical properties. The results are compared with those obtained for pure Al processed under similar conditions and for AA1050 aluminum. The yield stress of the nanocomposite with 1 vol pct SiC is more than ten times larger than that of AA1050. The largest increase is due to grain size reduction; nanocrystalline Al without SiC and processed by the same method has a yield stress seven times larger than AA1050. Adding 0.5 vol pct SiC increases the yield stress by an additional 47 pct, while the addition of 1 vol pct SiC leads to 50 pct increase relative to the nanocrystalline Al without SiC. Increasing the milling time and adding stearic acid to the powder during milling lead to relatively small increases of the flow stress. The hardness measured in nano- and microindentation experiments confirms these trends, although the numerical values of the gains are different. The stability of the microstructure was tested by annealing samples to 423 K and 523 K (150 °C and 250 °C) for 2 hours, in separate experiments. The heat treatment had no effect on the mechanical properties, except when treating the material with 1 vol pct SiC at 523 K (250 °C), which led to a reduction of the yield stress by 13 pct. The data suggest that the main strengthening mechanism is associated with grain size reduction, while the role of the SiC particles is mostly that of stabilizing the nanograins.     

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...     

Diffusivity of Ti-Ni Diffusion Couple Enhanced by Pulse Current During Spark Plasma Sintering

Metallurgical and Materials Transactions B - The effect of pulse current (PC) on the interdiffusion of Ti-Ni system was investigated under spark plasma sintering. The growth rate of Ni-Ti...     

放电等离子烧结的超细纯碳化钨的组织与性能

利用放电等离子烧结技术得到了近全致密的无粘结相超细纯碳化钨材料。烧结前后平均粒径达200nm的超细组织基本维持不变。该材料的硬度明显超过了常规的碳化钨基硬质合金，可以用作优异的硬质材料。     

Structure and Magnetic Properties of Sm2Fe17Nx Sintering Magnets Prepared by Spark Plasma Sintering

Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN, α-Fe and N2. When sintering temperature was only above 200 ℃ under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase of α-Fe in the magnets.     

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。     

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。     

Characterization of Oxide Dispersed AlCoCrFe High Entropy Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering

The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV₁ and 1,070 ± 20 HV₁ was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness.     

氧化锆基金属陶瓷放电等离子烧结制备与性能研究

氧化锆陶瓷材料的脆性限制了其在某些领域的应用。文章首创在氧化锆粉末中加入316L不锈钢粉,通过放电等离子烧结制备氧化锆基金属陶瓷。试验通过不同的成分配比和不同的烧结温度进行对比研究,采用金相分析、XRD、SEM/EDS等测试方法,对材料的微观结构和宏观性能等进行了表征与分析。并通过断口分析,讨论了Zr O2·316L金属陶瓷的增韧机理。结果表明:采用放电等离子烧结制备出的材料随相组成的成分所占比例的改变,其致密度、弯曲强度、横向断裂强度、断裂韧性都随之呈现出相应的变化规律;316L相以片状均匀分布在氧化锆基体中,在材料断裂时起到了颗粒/纤维增韧的作用。同时氧化锆部分以亚稳相t-Zr O2的形态存在,也起到了相变增韧的作用。     

Enhanced Dielectric Properties in Spark Plasma Sintered Zinc Titanate Ceramics

The ever increasing application of zinc titanate ceramics as a dielectric material in microwave devices and low temperature co-fired ceramics calls for the improvement in their dielectric properties. In this paper, the effect of different sintering techniques on the dielectric properties of zinc titanate have been discussed. Zinc titanate was prepared by ball milling 1:1 molar ratio of ZnO and TiO₂ for 12 h and calcined at 800 °C for 2 h. The presence of ZnTiO₃ and Zn₂TiO₄ phases were confirmed by X-ray diffraction and the dielectric properties of the sintered samples were studied using LCR meter. Samples consolidated by spark plasma sintering (SPS) showed highest densification (13% increase), higher dielectric permittivity (?_r = 25.17) and Q factor (Q factor = 162.78) with lower loss tangent values (tanδ = 0.00614) than that of microwave sintered samples (?_r = 21.86, Q factor = 99.08, tanδ = 0.01009) and conventionally sintered samples (?_r = 20.54, Q factor = 60.07, tanδ = 0.01665). The fabrication time was considerably reduced for the materials prepared via SPS than that prepared by conventional route with improved properties and also the dependence of dielectric properties on density was confirmed in this research work.     

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...     

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.

     

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...     

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.