放电等离子烧结TiB/Ti-1.5Fe-2.25Mo复合材料的微观组织与力学性能

采用放电等离子烧结技术原位合成了TiB增强Ti?1.5Fe?2.25Mo复合材料,研究了烧结温度对复合材料微观组织和力学性能的影响规律。结果表明,随着烧结温度的升高,钛合金中 TiB 晶须的长细比迅速减小;然而,复合材料的相对密度及TiB的体积含量随着烧结温度的升高而不断增大。由于TiB晶须长细比的减小会导致复合材料强度的降低,而复合材料的相对密度及TiB体积含量的增大又会带来复合材料强度的增加,因此,在这两种因素的共同作用下,最终导致 TiB/Ti?1.5Fe?2.25Mo复合材料的弯曲强度随着烧结温度的升高而缓慢增大。在烧结温度为1150°C 时,TiB/Ti?1.5Fe?2.25Mo复合材料具有最大的弯曲强度1596 MPa。     

高钛渣还原的氢化钛合金粉一步烧结制备高强钛合金（英文）

提出一种直接利用高钛渣制备高强钛合金的方法。先用镁粉还原高钛渣制备氧含量为1.3%(质量分数)的合金粉末,再将合金粉末在600 MPa压力下压制成小圆柱体,最后在氩气下烧结成钛合金产品。对还原粉末进行表征,研究烧结温度对烧结合金的烧后密度、抗压强度、显微组织和硬度的影响。结果表明,随着烧结温度由900℃升高至1200℃,钛合金的密度增加,孔隙率降低,实现较好的烧结致密化(1100℃为98.65%,1200℃为99.41%),在1100℃时硬度达到HV 655.7,压缩强度为1563 MPa。     

Electrophysical properties of ceramic–polymer composite films as function of sintering temperature

The effect of changes in sintering temperature on electrical properties and microstructure of ZnO–polyaniline– polyethylene composite ceramics, prepared in disk form at the pressure of 60 MPa and at five different temperatures, has been investigated. Increasing sintering temperature from 30 to 120 °C noticeably reduces breakdown voltage from 830 to 610 V. Further increase in sintering temperature causes breakdown voltage to increase. Interface voltage barrier height behaves differently when sintering temperature increases, which is in contrast to breakdown voltage behavior. These samples have a very low leakage current, a factor which indicates low degradation. Then again, the higher the sintering temperature gets, the less the nonlinear coefficient becomes. In addition, each sample has hysteresis which decreases through increase of sintering temperature up to 120 °C. Further increase in sintering temperature, however, causes the hysteresis loop to spread. Regarding UV spectra of the samples, it is revealed that there are three impurity levels whose behaviors against sintering temperature are subtractive. Analysis of composite samples by scanning electron microscopy indicates that their microstructure consists of grains and grain boundaries. Resistivity of grain boundaries is the main responsible factor for these changes in varistor characteristic as a function of sintering temperature.     

微波烧结工艺对钨基合金挤压棒坯显微组织及力学性能的影响

研究了微波烧结温度和时间对钨基合金挤压棒坯显微组织及力学性能的影响。采用高倍SEM和光学金相显微镜分别对合金断口和显微组织进行了形貌观察;对合金相对密度、抗拉强度、延伸率和硬度进行了测定和分析。结果表明:当微波烧结时间为30min时,随着烧结温度的升高,合金性能呈峰值变化,烧结温度为1550℃时,合金的力学性能达到极大值,相对密度、抗拉强度、延伸率和HRC硬度分别为98.3%、920MPa、9.7%和30.5;当微波烧结温度为1550℃时,随着烧结时间的延长,合金的力学性能先上升后下降;随着微波烧结温度的升高及微波烧结时间的延长,钨晶粒的尺寸逐渐增大。     

Effects of various sintering methods on microstructure and mechanical properties of CP-Ti powder consolidations

Effects of various sintering methods such as spark plasma sintering (SPS), hot pressing (HP) and electric resistance sintering (ERS) on the microstructure and mechanical properties of commercial pure titanium (CP-Ti) powder consolidations with particle size of <147 μm, <74 μm and <43 μm were studied. The smaller particle powders are densified to proceed at a higher rate. Dense titanium with relative density up to 99% is found to take place at 850 °C under 30 MPa of SPS and HP condition. However, in case of ERS, CP-Ti powders were densified almost at 950 °C under 30 MPa. The microstructure of sintered titanium is composed of equiaxed grains at 850–950 °C. The yield strength of sintered body composed of <43 μm powder is 858 MPa by using SPS at 850 °C under 30 MPa. When there is a higher content of small particle, the higher yield strength value is obtained both by using SPS and HP. However, when ERS is introduced, the highest yield strength is 441 MPa at 950 °C under 30 MPa, which shows much lower values than those by SPS and HP methods. ERS method takes much less sintering time compared with SPS and HP. Nevertheless, higher sintering temperature results in lower strength and elongation because of brittle fracture.     

高体积含量TiC/Fe复合材料的制备及力学性能

以TiC粉、还原铁粉和羰基铁粉为原料,采用行星球磨混料、冷压成型后无压烧结工艺制备了TiC颗粒体积含量为70%~90%的TiC/Fe复合材料,重点研究了羰基铁粉添加量、烧结温度及TiC体积含量对TiC/Fe复合材料的微观结构和力学性能的影响。结果表明:羰基铁粉的最佳添加量为铁基体粉体积含量的60%。当TiC体积含量一定时,随烧结温度的升高,TiC/Fe复合材料的相对密度、维氏硬度与弯曲强度均先增大后减小,经1500℃烧结后,复合材料的综合性能最佳。其中,70%TiC/Fe的相对密度及弯曲强度最高,分别为99.5%和437MPa;80%TiC/Fe的维氏硬度最大,为12.2GPa。     

微波LTCC环行器用热压烧结SrFe12O19铁氧体的低温烧结特性

为了与低温共烧陶瓷（LTCC）技术兼容,本文采用热压烧结工艺在870 °C制备了添加不同Bi2O3含量的SrFe12O19铁氧体材料,着重研究了材料的晶相组成、烧结密度、气孔率和磁性能等低温烧结特性。研究结果表明,材料在870 °C烧结时,Bi2O3的添加促进了SrFe12O19晶相结构的形成,提高了材料的烧结致密度和磁性能。当Bi2O3的添加量为2～4 wt %,材料可以获得致密的结构,烧结密度达到4.65 g?cm-3以上,气孔率低于10%,材料的饱和磁化强度Ms和内禀矫顽力Hci较高,分别达到252.4 kA?m-1和312.9 kA?m-1以上。此外,基于SrFe12O19材料的低温烧结特性讨论了该材料在微波LTCC环行器当中的应用。     

Effect of Compaction Load and Sintering Temperature on Tribological and Mechanical Behavior of Ni/SiC/MoS<Subscript>2</Subscript> Composites

In the present investigation, the effects of compaction load and sintering temperature on the tribological and mechanical behavior of Ni/20%SiC/7%MoS₂ hybrid composites was studied. The density, compression strength, and hardness of the composites were evaluated and compared. The wear properties of the composites were evaluated for the test condition of 1 m/s speed and 10 N load using a pin-on-disk tribometer. The braking performance of the composites was evaluated in a subscale dynamometer for the 500 kJ energy condition. The microstructure and wear surface morphology of the composites were analyzed by stereo, optical, and scanning electron microscopes. From the results, the following important conclusions are drawn: (1) the compaction load of 1400 kN and sintering temperature of 900 °C are optimum to obtain the best combination of tribological and mechanical properties; (2) the properties such as density, compression strength, hardness, wear, and friction increase up to a critical sintering temperature, and then decrease later; (3) the composition and thickness of the interface reaction product phases (Ni₂Si, Ni₃Si, and graphite) play a key role in deciding the strength of Ni/SiC interface that consequently affects the mechanical and tribological properties of the composites; (4) the abrasive wear is found to be the main wear mechanism in the highly densified composites, whereas the delamination wear and the third-body wear are major wear mechanisms in the poorly densified composites; and (5) the better braking performance of the highly densified composites is attributed to the absence of third-body wear, controlled flow of solid lubricant, and lower porosity.     

烧结温度对振荡压力烧结工艺制备高性能氧化锆陶瓷的影响

采用新型振荡压力烧结技术制备了高性能氧化锆陶瓷,并系统研究了该工艺中烧结温度对于氧化锆陶瓷中致密度、晶粒尺寸、微观结构以及力学性能的影响。结果表明:在振荡压力烧结工艺下,随着烧结温度的提高,氧化锆试样致密度变化不明显,但晶粒尺寸不断增加,试样表面均几乎无气孔。当目标温度达到1300℃时,氧化锆陶瓷的硬度和抗弯强度均最大,分别为16.6 GPa和1455 MPa。相比常压和热压烧结工艺,振荡压力的引入明显降低了氧化锆陶瓷的致密化温度,且获得了更高的力学强度和断裂可靠性。     

Sintering Behavior of Elemental Powders with FeB Addition in the Composition of Martensitic Stainless steel

The effect of sintering additive for the development of high-strength martensitic stainless steel from elemental powders was studied. The sintering parameters investigated were: sintering temperature, sintering time, and wt.% of FeB. In vacuum sintering, effective sintering took place between 1300 and 1350 °C with 1-1.5 wt.% FeB addition. The maximum sintered density and ultimate tensile strength (UTS) were achieved after sintering at 1350°C for 60 min with 1 wt.% FeB. Secondary pores were observed in samples containing more than 1.5 wt.% FeB sintered at 1350 °C for 60 min. More than 1.5 wt.% FeB content and temperature above 1350°C caused slumping of the specimens. Maximum UTS of 505 MPa was achieved with 1 wt.% FeB content. Above 0.5 wt.% FeB content, maximum increase in density was observed. Fracture morphologies of the sintered samples are reported.     

放电等离子烧结压力对超细WC-Co硬质合金性能的影响

通过分析放电等离子烧结致密化过程,确定了致密化温度;研究了SPS烧结过程中压力对WC-Co硬质合金致密化、显微组织及性能的影响。结果表明,放电等离子烧结粉末在1 130℃时,达到最大收缩率;烧结压力的增加,样品的致密度、硬度增加;断裂韧性的变化集中在11.5~12.1 MPa.m1/2之间,和硬度的变化呈现相反的趋势;烧结压力相对较小时,样品WC晶粒较粗大且不均匀;在40 MPa和55 MPa时,晶粒相对较小且分布均匀。要得到高性能、高致密度的样品,合理的烧结温度在1 200℃以上,烧结压力为40 MPa。     

Effects of porous carbon on sintered Al-Si-Mg matrix composites

The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO₂ gas flow. Activated char particles at 0.02 V _f were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 °C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 °C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6 %, respectively; with increasing surface area of the reinforcement from 123 to 821 m²g⁻¹. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13 % (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16 % (11.7 × 10⁻⁶ to 9.8 × 10⁻⁶ °C⁻¹), and remained unaffected at more than 35 % burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds. J.U. Ejiofor, formerly of the Department of Metallurgical and Materials Engineering, The University of Alabama     

Warm compacted NbC particulate reinforced iron-base composite(Ⅱ)--Microstructure and properties

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海绵钛电极块压制模具的结构优化

采用纳米银薄膜作为研究对象,在250℃下施加5~10 MPa的烧结压力,获得低孔隙率(1.2%~1.4%)的高质量烧结接头。随着烧结压力由5 MPa增大至10 MPa,接头抗剪切强度显著提升。借助深腐蚀技术对烧结接头及块体银的微观组织结构进行对比分析。结果表明,烧结接头的深腐蚀形貌与块体银存在明显差异。烧结接头在深腐蚀条件下呈现大量微米尺度的多边形银晶粒,当烧结压力由5 MPa增大至10 MPa时,多边形晶粒的尺寸与晶粒间的连接面积发生明显变化。这一现象是影响纳米银压力烧结连接接头性能的主控因素。     

A novel approach to boriding of TZM by spark plasma sintering method

Boriding can be candidate method to increase mechanical properties and oxidation resistance of molybdenum based alloys. Rapid oxidation of TZM at elevated temperature and low wear resistance are considered to be main drawbacks for possible applications. In this study molybdenum boride layer was formed on the surface of TZM by spark plasma sintering (SPS) method. Pre-mixed TZM was used as a raw material in powder form. Both sintering and boriding process were performed in a single step at constant temperature of 1420 °C in various pressures (40–60 MPa) and holding times (5–15 min) under vacuum. The effects of molybdenum boride layer on density, hardness and oxidation behavior were investigated. Thickness, microstructure and hardness of Mo-B based protective layer showed a variety with different process parameters. The boride layer thickness was reached to approximately 200 μm by increasing pressure and holding time. Formation of this layer provided a decrease in mass loss about 73.4% during oxidation test at 1000 °C for 60 min. The maximum surface hardness value was obtained as 21.4 GPa while hardness of base metal was 2.3 GPa.     

Preparation and sintering properties of zirconia-mullite-corundum composites using fly ash and zircon

Zirconia-mullite-corundum composites were successfully prepared from fly ash,zircon and alumina powder by a reaction sintering process.The phase and microstructure evolutions of the composite synthesized at desired temperatures of 1 400,1 500 and 1 600°C for 4 h were characterized by X-ray diffractometry and scanning electronic microscopy,respectively.The influences of sintering temperature on shrinkage ratio,apparent porosity and bulk density of the synthesized composite were investigated.The formation process of the composites was discussed in detail.The results show that the zirconia-mullite-corundum composites with good sintering properties can be prepared at 1 600°C for 4 h.Zirconia particles can be homogeneously distributed in mullite matrix,and the zirconia particles are around 5μm.The formation process of zirconia-mullite-corundum composites consists of decomposition of zircon and mullitization process.     

碳黑含量对放电等离子烧结Fe-Cr-C/TiCN复合材料组织和耐磨性的影响

采用机械合金化和放电等离子烧结法制备了不同碳含量的Fe-Cr-C/TiCN复合材料。通过扫描电镜、X射线衍射、维氏硬度和球-盘式摩擦试验,系统地研究了碳含量对Fe-Cr-C/TiCN复合材料组织和磨损性能的影响。结果表明,在含碳量为1.0%~5.0%（质量分数,下同）的烧结样品中形成了(Cr, Fe)₇C₃碳化物,而当碳含量达到4.0%~5.0%时,出现了(Cr, Fe)₃C相。碳含量对Fe-Cr-C/TiCN复合材料的组织均匀性和致密化有着较为重要的影响,当烧结温度为~1000 ℃时,致密度由未加碳时的95.0%提高到的99.7%（含碳量为3.0%）,说明已实现了完全致密化。当含碳量为3.0%时,维氏硬度达到11 940 MPa。此外,添加适量的碳（3.0%）有助于获得良好的磨损性能,即摩擦系数波动范围小,平均摩擦系数为0.320,磨损率为6.8×10^-4 mm³·N^-1·m^-1。     

Effects of (Ti,W)C Addition on the Microstructure and Mechanical Properties of Ultrafine WC-Co Tool Materials Prepared by Spark Plasma Sintering

In this study, powder mixtures containing (Ti, W)C additions (10, 20, 30 and 40 wt%) were prepared and then consolidated at 1200, 1250, 1300 and 1350 °C by spark plasma sintering. The effect of (Ti, W)C additions on the microstructure and mechanical properties of ultrafine WC-Co materials was investigated. The results demonstrate that the (Ti, W)C not only retards the sintering densification but also increases the porosity of sintered samples. The increasing sintering temperature is beneficial to the densification but results in the grain coarsening and the dissolution of W in (Ti, W)C. Moreover, there are no (Ti, W)C grains with obvious core/rim structure in the microstructure. With the (Ti, W)C increasing from 10 to 20 wt%, the hardness increases and fracture toughness changes hardly. However, the hardness and fracture toughness decrease slightly as the (Ti, W)C further increases. The transgranular fracture of (Ti, W)C phases is responsible for the slight reduction in fracture toughness. The sample with 20 wt% (Ti, W)C has high hardness and fracture toughness (H_V: 21.3 GPa, K_IC: 9.8 MPa m ^1/2).     

Y2O3含量和烧结温度对ODS镍基合金性能的影响

采用粉末冶金技术,以不同质量分数(0%～10%)Y2O3为弥散相,用不同的烧结工艺制备出ODS(oxide dispersion strengthened)镍基高温合金,借助XRD,OM,SEM,EDAX研究了氧化物含量和烧结温度对ODS镍基高温合金性能的影响。结果表明:含1.5%Y2O3经1260℃保温2h真空烧结的试样具有较佳的综合性能,相对密度为90.9%,抗拉强度为669MPa。对用不同球磨工艺制备的合金粉末进行XRD物相分析,并从试样断口显微组织、微区成分上分析氧化物含量和烧结工艺对合金力学性能产生影响的机制。     

Thermal conductivity behavior of SPS consolidated AlN/Al composites for thermal management applications

AlN/Al composites are a potentially new kind of thermal management material for electronic packaging and heat sink applications.The spark plasma sintering (SPS) technique was used for the first time to prepare the AlN/Al composites,and attention was focused on the effects of sintering parameters on the relative density,microstructure and,in particular,thermal conductivity behavior of the composites.The results showed that the relative density and thermal conductivity of the composites increased with increasing sintering temperature and pressure.The composites sintered at 1550 ℃ for 5 min under 70 MPa showed the maximum relative density and thermal conductivity,corresponding to 99% and 97.5 W m-1 K-1,respectively.However,the thermal conductivity of present AlN/Al composites is still far below the theoretical value.Possible reasons for this deviation were discussed.