Governed by: China Association for Science and Technology
Sponsored by: Chinese Mechanical Engineering Society, The Chinese Society for Metals, The Nonferrous Metals Society of China, University of Science and Technology Beijing
Published by: Editorial Office of Powder Metallurgy Technology
Editor-in-Chief: QU Xuan-hui
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Email: pmt@ustb.edu.cn
Standard Number: ISSN 1001-3784CN 11-1974/TF
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Silicon nitride (Si3N4) is considered to be the best ceramic material for the comprehensive properties. High thermal conductivity and the excellent mechanical properties make it widely used as the ceramic substrate in electric vehicles and hybrid electric vehicles (EV/HEV). Sintering additives have the great influence on the sintering activity, microstructure, and the second phase composition of silicon nitride, and then affect the thermal conductivity of ceramics. Selecting the suitable sintering additives is very important for the preparation of high thermal conductivity silicon nitride ceramics. The research status of sintering additives used for the preparation of high thermal conductivity silicon nitride ceramics was summarized in this paper, the influence of sintering additives on the thermal conductivity and mechanical properties of silicon nitride ceramics was analyzed, and the future research direction and development trend of sintering additives were put forward.
With the continuous improvement on the preparation process of the carbon nanotube-reinforced aluminum matrix composites, the difficult dispersion problem of the carbon nanotubes has been properly solved, and the composite strength has been improved, but the high modulus and high strength of the composites have not been fully utilized, and the “strength-plastic” inversion phenomenon has appeared. The adjustment methods of interface structure, grain structure, and composite configuration design of the carbon/aluminum composites in recent years were summarized in this paper, the influence of interface structure strength on the load transfer efficiency of the carbon nanotubes was discussed, the causes of inversion phenomenon were analyzed, and the control ideas were proposed to solve the problem of poor plastic toughness of the composites, providing the basis for preparing the carbon nanotube-reinforced aluminum matrix composites with high strength and toughness.
AlN ceramics were prepared by spark plasma sintering (SPS) using the pure nano-AlN powders and the nano-AlN powders doped by 3% Y2O3 (mass fraction) as the raw materials. The relative density, microstructure, mechanical properties, and thermal conductivity of two types of AlN ceramics were studied. The results show that, both the pure nano-AlN powders and the nano-AlN powders doped by Y2O3 can obtain the AlN ceramics with the relative density above 99% prepared by SPS at 1500 ℃ for 5~60 min under 40~60 MPa. When the sintering pressure is 50 MPa, the average grain size of the AlN ceramics is the smallest, which is 176 nm and 190 nm, respectively. The hardness and bending strength of the AlN ceramics are obviously improved by the grain refinement. When the sintering time is extended from 5 min to 60 min, the grain size of the AlN ceramics is increased to 1.71 μm and 1.73 μm, respectively. The grain growth leads to the decrease of hardness and bending strength of the AlN ceramics, but improves the thermal conductivity. It is found that the addition of Y2O3 sintering agent can effectively improve the comprehensive properties of the AlN ceramics under the same SPS sintering process.
The thermal compression deformation behaviors of the hot extruded (HEX) FGH95 alloys were investigated systematically using the Gleeble 3800D thermal-mechanical simulator in the strain rate of 0.001~1.000 s−1 at the deformation temperature range of 1050~1120 ℃. The constitutive equations of the hot extruded FGH95 alloys were derived from the stress-strain curves obtained in the isothermal compression tests. Furthermore, the hot processing maps were established based on the dynamic models. In the results, the corresponding material constants of the constitutive equation are determined as Q=300.925 kJ·mol−1, α=0.01139 MPa−1, and n=1.86. Compared with the hot isostatic pressing (HIP) alloys, the activation energy of the hot extruded FGH95 alloys is declined by more than 50%. According to the energy dissipation efficiency and the microstructure analysis of the hot extruded FGH95 alloys, the processing safety zone and instability zone are identified during the hot extrusion process. Ultimately, the optimal processing conditions of the FGH95 alloys are proposed as the strain rate of 0.010~0.100 s−1 and the deformation temperature of 1050~1120 ℃.
(Cr,La)2(C,N) powders were prepared by the high temperature carbon tube furnace in an open system, using as the additive to prepare the Ti(C,N)-based cermets. The effects of (Cr,La)2(C,N) on the microstructure and mechanical properties of the Ti(C,N)-based cermets were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), universal mechanical testing machine, and Vickers hardness tester. The results show that the addition of (Cr,La)2(C,N) can effectively refine the hard phase grains of the Ti(C,N)-based cermets. The Cr and La elements are mainly dissolved in the binder phase, and the La element promotes the dissolution and precipitation process of the hard phase. Furthermore, the bending strength, hardness, and fracture toughness of the cermets are significantly improved. When the mass fraction of (Cr,La)2(C,N) is 5.0%, the comprehensive mechanical properties of the Ti(C,N)-based cermets are the best, the bending strength is 2002 MPa, the Vickers hardness is 1643 MPa, and the fracture toughness is 11.22 MPa·m1/2.
TiCN–WC–HfN ceramics were prepared by vacuum hot pressing sintering technology, and the effects of Re contents (molar fraction) on the microstructure and mechanical properties of the ceramics were investigated. The results show that, the TiCN–WC–HfN–Ni–Re ceramics are composed of TiC0.41N0.5, WC, HfN, TiC, Ni and Re, and TiC0.4N0.50 is the solid solution formed between TiC and TiN in the sintering process. Micro-pits and cleavage planes are discovered in the fracture surface of TiCN–WC–HfN ceramics with the different molar fraction of Re. When the molar fraction of Re is 2.5%, there are more micro-pits on the ceramic fractures. When the mole fraction of Re increases from 0 to 3.0%, the Vickers hardness, flexural strength, and fracture toughness of the TiCN–WC–HfN ceramics first increase and then decrease. When the mole fraction of Re is 2.5%, the mechanical properties of the ceramics show the best as the Vickers hardness is (19.25±0.21) GPa, bending strength is (1304±23) MPa, and fracture toughness is (7.73±0.22) MPa∙m1/2. Transgranular fracture and intergranular fracture of the TiCN–WC–HfN–Ni–Re ceramics occur during the fracture process, and the toughening mechanisms are the crack deflection and crack bridging.
As a new type of functional and structural material, the porous metal materials have been widely used in the fields of sound absorption, energy absorption, fluid distribution, heat exchange, catalysis, filtration, and separation, which are the most widely used in the field of filtration and separation. Porous metal materials can achieve the liquid−solid and gas−solid filtration separation for the different fluids in the fields of petroleum and petrochemical, fine chemical, coal chemical, and other fields, and the requirements for the materials and mechanical properties of the porous metal materials used in the different fields are also different. The preparation process of porous metal materials used for filtration is relatively mature, but there is little investigation on the corrosion resistance and mechanical properties of the porous metal materials, which will directly affect the use effect and life of such materials. The research progress on the mechanical properties and corrosion resistance of the porous metal materials used for filtration in recent years was briefly reviewed in this paper, and the existing problems in the corrosion and mechanical behavior of such materials were discussed. Finally, the research direction of the porous metal materials used for filtration was prospected.
Fe–Cr alloy powders were prepared by vacuum close-coupled gas atomization technology. The effects of the diameter and protrusion length of the melt delivery nozzle on the size distribution, yield, and median particle size (D50) of the Fe–Cr alloy powders were studied. The results show that, when the diameter of the melt delivery nozzle increases from 4.5 mm to 6.0 mm, the size accumulation distribution curve of the Fe–Cr alloy powders shifts to the right, the median particle size increases, the fine powder yield decreases, the powder fluidity decreases, and the apparent density decreases. When the protrusion length of the melt delivery nozzle increases from 2.0 mm to 2.5 mm, the size accumulation distribution curve of the Fe–Cr alloy powders shifts to the left, the median particle size decreases, the fine powder yield increases, the powder fluidity increases, and the apparent density increases. Combined with the experimental data analysis, the best comprehensive properties of the Fe–Cr alloy powders are obtained under the condition as the atomization pressure of 3.8 MPa, the superheat of 250 ℃, the nozzle diameter of 4.5 mm, and the nozzle protrusion length of 2.5 mm.
S590 powder metallurgy high speed steels (S590 HSS) were prepared by plasma rotating electrode atomization and hot isostatic pressing. The S590 HSS samples were quenched at 1050, 1100, 1150, and 1180 ℃, respectively, followed by the tempering at 550 ℃ for 1 h (once), −196 ℃ cryogenic treatment for 4 h (once), and tempering at 550 ℃ for 1 h (twice). The effect of quenching temperature on the microstructure and mechanical properties of S590 HSS was studied. The results show that, the microstructure of S590 HSS after the heat treatments mainly consists of martensite, M6C carbides, and MC carbides. With the increase of quenching temperature, the carbides gradually dissolve into the matrix, the carbide content decreases, and the matrix grain size increases. The hardness and compressive strength of S590 HSS increase with the increase of quenching temperature. After quenching at 1180 ℃ and the subsequent heat treatments, the hardness of S590 HSS is up to HRC 67.8, and the compressive strength is 3827 MPa. With the increase of quenching temperature, the bending strength first increases and then decreases, and the impact toughness decreases. The bending strength of the samples quenched at 1100 ℃ reaches the highest as 5473 MPa. The impact toughness of the samples quenched at 1050 ℃ reaches the highest as 76.9 J·cm−2. Considering the microstructure and mechanical properties, the optimum quenching temperature of S590 HSS is 1100 ℃.
Due to the low amorphous forming ability and the poor room temperature plasticity, the engineering applications of Fe-based amorphous alloys were greatly limited. Based on the design concept of “near mixing enthalpy with effective atomic size difference”, the Fe55Nb15Ti15Ta15 metal component powders were designed, and the amorphous alloy powders were successfully prepared by mechanical alloying. The effects of TiC ceramic powders doped during the mechanical alloying on the amorphous forming ability, microstructure, and thermal stability of the Fe55Nb15Ti15Ta15 alloy powders were studied. The results show that, the Fe55Nb15Ti15Ta15 alloy powders have the good amorphous forming ability and thermal stability, the TiC ceramic powders are uniformly and stably distributed in the Fe55Nb15Ti15Ta15 amorphous alloy powders. The addition of 15% TiC ceramic powders (mass fraction) delays the alloying and amorphization process of Fe55Nb15Ti15Ta15 alloy powders during ball milling, reduces the thermal stability, and makes the particle size of powders smaller and the distribution range wider after ball milling. This process can produce the large bulk Fe-based amorphous alloy powders with the high room temperature plasticity.
EHV/UHV power transmission is the core technology to realize the global energy interconnection. As the most widely used conductor materials in power transmission system, the corrosion resistance of copper and copper alloys has been paid more attention. In the process of EHV/UHV DC transmission, there is a large magnetic field in the surrounding environment, which leads to the service environment of the copper components different from that of the ordinary transmission environment. The electrochemical corrosion behavior of the pure copper under the EHV/UHV environment was studied by potential polarization, electrochemical impedance spectroscopy, and element analysis in this paper. The results show that, the limiting diffusion current of the pure copper in 3.5% NaCl solution (mass fraction) under the UHV/UHV environment is larger than that without magnetic field, and the reaction resistance without magnetic field is significantly increased compared with that under 0.1 T magnetic. Combined with the results of electrochemical impedance spectroscopy, X-ray diffraction, and elemental analysis, it is shown that the high-intensity magnetic field (0.1 T) can reduce the corrosion resistance of the pure copper, and the main corrosion product is Cu2O.
本文通过对泡沫金属国内外发展的概况的介绍,主要内容包括泡沫金属基本概念,制备方法,泡沫铝、泡沫镁、泡沫钛、泡沫铜、泡沫铁的制备与应用研究,泡沫金属的特征及应用等,以对泡沫金属的发展现状、研究与应用有一个较全面的认识.
超级电容器作为一种新型储能元件,以其优异的电化学特性和环境友好性,受到广泛关注.超级电容器主要分为双电层电容和法拉第赝电容,分别通过电极/电解液界面的双电层和电极表面的可逆反应储能.超级电容器同时具有较高的功率密度和能量密度,这很大程度上归功于性能优良的电极材料.超级电容器的电极材料主要包括碳材料、导电聚合物材料和金属化合物材料.本文主要概述了超级电容器的分类、原理,以及三种电极材料的性能特点和发展现状.
利用放电等离子烧结技术(SPS)制备了Y-TZP氧化锆陶瓷,研究了Y-TZP氧化锆陶瓷应力诱导相变增韧机理.结果表明:氧化锆陶瓷晶粒尺寸大于临界相变尺寸时,t相会自发转化为m相,降低断裂韧性;当晶粒尺寸小于临界相变尺寸时,介稳t相可在应力诱导下可以发生t相向m相转变,且晶粒尺寸越大,相变量越大,提高材料的断裂韧性.晶粒尺寸是影响应力诱导相变量的主要因素,两者呈近似线性递增关系;随着晶粒尺寸的增加,断裂韧性先减后增,近似呈抛物线关系.
综述了机械合金化、机械研磨以及机械涂覆三种机械球磨技术在材料制备领域中的应用和作用机理,讨论了三种机械球磨技术在材料制备中的优势与弊端,展望了该技术的今后发展方向。
铁氧体吸波材料具有价格低廉、吸收效率高、涂层薄、频带宽等优异特性,因此有着广泛的应用前景.本文阐述了铁氧体磁性材料的吸波原理,介绍了铁氧体吸波材料的分类,总结了铁氧体吸波性能的影响因素.
钛及钛合金兼具低比重、高比强度、优异的生物相容性和良好的耐腐蚀性,在航空航天、生物医疗、化工、汽车等领域有极大的应用潜力.钛及钛合金金属粉末注射成形技术(metal injection molding,MIM)能够实现中小型复杂形状钛产品的大批量、低成本制备,对于推动钛及钛合金产品的生产及应用具有重要意义.本文介绍了金属粉末注射成形钛及钛合金的特点及优势,从粉末原料、黏结剂体系、粉末注射成形、脱黏和烧结等方面综述了钛及钛合金金属粉末注射成形技术的研究进展,并针对目前存在的主要问题,分析了金属粉末注射成形钛及钛合金的研究方向及发展前景.
超高分子量聚乙烯纤维(UHMWPE)是一种新型高性能纤维,但是由于纤维高取向度、表面惰性,造成纤维与树脂之间的界面粘结强度低,限制了纤维的应用.因此,必须对纤维表面进行改性.本文详细介绍了超高分子量聚乙烯纤维表面改性常用的几种方法.有化学试剂处理、等离子体处理、电晕放电处理、辐射引发表面接枝处理、化学交联处理等.由于方法单独使用均存在不足之处,所以最好是几种方法联合使用,各取所长,取利避害,以提高纤维及其复合产物的综合性能.
通过真空激光熔覆制备了AlCoCrCu0.5FeMoNiTi高熵合金涂层.用电阻炉对涂层进行500 ~900℃的退火处理.使用X射线衍射仪、扫描电子显微镜、显微硬度计对涂层的组织结构和硬度进行了分析.结果表明,涂层为BCC结构,晶格常数a为0.291 nm.涂层经过抛光和王水腐蚀后,形貌为树枝晶特征,结晶细密.合金在500 ~900℃退火处理后仍保持BCC结构,未见有其他析出相,说明合金的具有很好的热稳定性.熔覆态合金的硬度达到1080 HV.经500℃退火后,涂层硬度下降了100 HV,但再升高退火温度,硬度变化极小,在900℃退火后,硬度仍然达到943 HV,说明AlCoCrCu05FeMoNiTi高熵合金涂层具有很好的抗高温软化性能.
纯金属钼存在低温脆性、再结晶脆性、抗高温氧化能力较差等明显缺点,极大限制了其应用范围,通过在钼基体中添加第二相(稀土氧化物(La2O3、Ce2O3、Y2O3)和碳化物(TiC、ZrC、HfC))形成的钼合金因具有良好的高温性能、较低的韧脆转变温度、较高的再结晶温度受到了国内外学者的广泛关注.本文对三种钼合金制备工艺(固-固掺杂、固-液掺杂和液-液掺杂)进行了总结,并对其发展趋势做出了展望,结果表明采用液-液掺杂工艺能显著提高材料的均匀性和力学性能.
采用真空熔炼气雾化工艺制备3D打印用316L不锈钢粉末,通过调整雾化参数,研究了不同雾化压力对粉末化学成分、粒度分布、球形度、表面形貌、流动性及松装密度等特性的影响.结果表明:在保温温度(1560±20)℃、保温时间20 min、漏包温度(1050±30)℃、高纯氮气雾化及雾化压力3.0 MPa工艺参数下,制备得到的粉末性能可达到氧含量(质量分数)0.08%、中位径31.39 μm、球形度0.75、流动性21.56 g/(50 s)及松装密度3.88 g/cm3,基本满足不同金属3D打印技术对粉末材料性能的要求.