细晶粒Ti（C，N）基金属陶瓷的研究进展

综述了细晶粒Ti（C,N）基金属陶瓷的研究现状,简要分析了原始粉末粒径、烧结工艺、烧结方法对其性能的影响,介绍了几种新的制备方法,指出必须发展新的制备技术,以充分发挥细晶粒金属陶瓷的优越性。     

超细/纳米粉末改进Ti(C,N)基金属陶瓷性能研究进展

综述了近几年超细或纳米粉末改进Ti(C,N)基金属陶瓷性能的方法,简要分析了含超细或纳米粉末Ti(C,N)基金属陶瓷的致密化问题.总结了真空烧结 热等静压处理和放电等离子烧结的特点,并分析了微波烧结和等离子活化烧结制备Ti(C,N)基金属陶瓷的可能性.     

Si_3N_4晶须对TiC_(0.7)N_(0.3)-WC-TaC-Mo-(Ni,Co)金属陶瓷组织和性能的影响研究

采用粉末冶金工艺制备了含有不同亚微米级Si3N4晶须含量的Ti(C,N)基金属陶瓷材料。利用密度测试仪、抗弯强度测试仪、维氏硬度测试仪、X射线衍射分析仪和扫描电镜等仪器设备检测分析了材料的力学性能和组织结构,研究了亚微米级Si3N4晶须对Ti(C,N)基金属陶瓷材料的组织结构和性能的影响。结果表明,本实验采用的球磨混料工艺,能较好地将各原始组元充分分散,均匀分布。添加到Ti(C,N)基金属陶瓷材料中的Si3N4晶须能通过桥联和拔出机制增加材料断裂韧性,提高材料断裂强度和显微硬度。但是,大长径比Si3N4晶须会引起材料孔隙率上升,对材料性能产生不利影响。     

纳米Ti(C,N)增强Ti(C,N)基金属陶瓷的制备研究

采用Ti(C,N)纳米粉末制备Ti(C,N)基金属陶瓷.研究了烧结温度、保温时间和升温速度等工艺参数对含10wt％纳米粉末的Ti(C,N)基金属陶瓷性能的影响,得到优化烧结工艺为1450℃,保温75min,升温速度3℃/min.用优化工艺制备的Ti(C,N)基金属陶瓷抗弯强度提高了约36.7％,增强机理主要表现为细晶强化、弥散强化和固溶强化.     

烧结温度和粉末预处理对SPS制备超细晶硬质合金的影响

采用亚微米WC粉和微米Co粉混合粉末作为原料,利用高能球磨与放电等离子烧结(SPS)技术制备超细晶WC-10Co硬质合金.研究表明,球磨后直接烧结时,当温度由1150℃增加到1200℃,试样的晶粒尺寸和硬度没有明显变化(平均晶粒尺寸约250nm),但致密度提高至98.6%,横向断裂强度由1045MPa提高到1819MPa.当对球磨后的混合粉末进行900℃真空处理后,在较低温度烧结的条件下试样的致密度则高达99%,且横向断裂强度与未处理粉末在相同工艺下烧结获得提高.     

纳米晶Ti(C,N)固溶体粉末的制备及组织结构研究

研究了纳米晶Ti(C,N)固溶体粉末的碳热还原反应制备及其组织结构特征。结果表明．以球形亚微米TiO2粉末和纳米碳黑为原料，通过原料成分C／Ti的准确配比和适当的工艺参数，可制备出成分优良的晶粒度为37nm的单相纳米晶Ti(C，N)固溶体粉末。     

金属陶瓷刀具切削不锈钢的磨损机理研究

利用真空烧结工艺制备了纳米复合Ti（C，N）基金属陶瓷刀片。进行了奥氏体不锈钢的单因素切削试验，并利用SEM、EPMA对金属陶瓷刀具的磨损失效机理进行了详细的研究。结果表明：纳米复合Ti（C，N）基金属陶瓷刀片在切削奥氏体不锈钢时表现出较高的耐磨性，其主要的磨损失效机理为粘结磨损，同时伴随一定的氧化磨损和扩散磨损。     

Ti(C,N)基金属陶瓷的组织结构与合金化

Ti(C,N)基金属陶瓷的高温红硬性、耐磨性和抗氧化性好,与金属材料间的摩擦系数低,是制作工模具和耐磨零部件的理想材料.简要介绍了合金化成分对Ti(C,N)基金属陶瓷组织结构和力学性能的影响以及多元(Ti,M)(C,N)固溶体粉末制备和金属陶瓷烧结技术的研究现状.     

纳米TiC增强Ti(C、N)基金属陶瓷材料的组织与性能研究

采用自制的纳米TiC粉末制备Ti(C、N)基金属陶瓷。研究了纳米粉末对金属陶瓷组织及性能的影响。结果表明，粉末冶金过程中，纳米TiC粉末易于在粘结相中扩散与溶解及沿晶界分布．降低了硬质相在粘结相中的溶解度．抑制了晶粒长大，同时微观上造成局部富C和稳定了硬质相中的C含量，使金属陶瓷材料的环形相增多尺寸增厚。抗弯强度与晶粒尺寸满足于Hall-Petch公式，5％～10％(质量分数)的纳米粉末加入量可使金属陶瓷的抗弯强度得到较大的提高，但硬度与晶粒尺寸的关系反Hall-Petch公式。     

Ti(C,N)基金属陶瓷的烧结工艺研究

采用真空烧结工艺制备了Ti(C,N)基金属陶瓷,研究了烧结温度和保温时间对Ti(C,N)基金属陶瓷显微组织和力学性能的影响,并用SEM观察其断口形貌.结果表明:随着烧结温度的升高,金属陶瓷的组织逐渐变得均匀,硬质颗粒逐渐球化,且其环形相逐渐变得完整;温度过高,保温时间过长,晶粒都会明显长大,环形相变厚,导致材料性能下降.经1440℃烧结,保温60min,可获得较佳的性能,其抗弯强度达1914.2MPa,硬度HRA达90.1.     

Mechanical alloying and sintering of nanostructured tungsten carbide-reinforced copper composite and its characterization

Elemental powders of copper (Cu), tungsten (W) and graphite (C) were mechanically alloyed in a planetary ball mill with different milling durations (0–60 h), compacted and sintered in order to precipitate hard tungsten carbide particles into a copper matrix. Both powder and sintered composite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and assessed for hardness and electrical conductivity to investigate the effects of milling time on formation of nanostructured Cu–WC composite and its properties. No carbide peak was detected in the powder mixtures after milling. Carbide WC and W₂C phases were precipitated only in the sintered composite. The formation of WC began with longer milling times, after W₂C formation. Prolonged milling time decreased the crystallite size as well as the internal strain of Cu. Hardness of the composite was enhanced but electrical conductivity reduced with increasing milling time.     

纳米增强金属陶瓷的组织及热冲击性能

为了进一步提高金属陶瓷的力学性能及其刀具的高速切削性能, 研究了纳米增强金属陶瓷的显微组织特征和热冲击性能。扫描电镜和透射电镜分析表明: 组织中陶瓷相呈现典型的芯2壳结构特征; 芯为TiC 或Ti (C ,N) , 而壳则为( Ti ,Mo ,W) (C ,N) 固溶体。纳米增强金属陶瓷机制为细晶强化、弥散强化和固溶强化。热冲击实验表明: 随着热循环的进行, 材料中孔洞的数量、孔洞的尺寸以及微裂纹的尺寸随之增大; 同时, 热循环过程中出现的表面氧化、裂纹长大、偏转以及桥接现象也很显著。与常规Ti (C ,N) 金属陶瓷相比, 纳米增强金属陶瓷的抗热冲击性能明显提高。      

Mechanomaking of nanostructured hypereutectic white irons: powder fabrication

Abstract

White irons containing 5·7 wt-%C were produced by room temperature, high energy milling from iron and carbon elemental powders. Both iron and cementite phases have crystal sizes of less than 10 nm in the powders which have fully dense particles of 50 μm mean size. The gas content is 0·5 wt-% and the powder is stable up to 550°C. Above 550°C decomposition of cementite occurs, involving a decrease in combined carbon content from 5·7 to 3·5 wt-% (annealing at 1050°C). The crystal growth kinetics has two temperature regions with lower activation energies in the high temperature (above 800°C) region. Crystal sizes still below 100 nm were observed for annealing up to 800°C. The size distribution in mechanosynthesised powders was modified by tumbling (dry) and attritor (wet) milling down to mean sizes of 4 μm and 1·4 μm respectively. Whereas tumbling milling does not alter the properties of MS powders, wet attritor milling produced higher gas content (7 wt-%) and much decreased thermal stability. Mechanosynthesised and tumbling milled powders can be degassed prior to consolidation, while wet attritor milled ones cannot.     

Recycling process of WC-Co cermets by hydrothermal treatment

Hydrothermal extraction process of Co binder phase from WC-Co cermet was investigated in order to establish a novel recycling system of WC-Co cermet scraps. When the cermet chips were hydrothermal-treated in hydrochloric acid above 110^∘C, Co binding phase was efficiently extracted and the cermet chips were disintegrated into relatively large fragments. After hydrothermal treatment, WC sintered body become very brittle and pulverized easily by ball milling and the mean particle size of thus obtained WC particle became similar to that of virginal WC particle. The recycled WC powder was a little easier to undergo oxidation than the virginal WC powder, so that the mechanical properties of recycled WC-Co cermets were degraded. However, the degradation of mechanical properties was prevented only by drying the WC powder more carefully. This hydrothermal process will be one of the recycling systems for WC-Co cermets.     

The production of a Nd-Fe-B permanent magnet by a hydrogen decrepitation/attritor milling route

A bulk ingot of a Nd-Fe-B alloy has been powdered by a combination of hydrogen decrepitation and attritor milling. The powder was aligned and pressed in the hydrided condition and the green compact sintered at 1080? C for 1 h after an appropriate heating rate. Excellent densities were achieved after this procedure and the magnets produced by this method exhibited energy products in the region of 250 kJm^?3 (32 M GOe).     

Synthesis and characterization of Al-Zn/Al2O3 nano-powder composites

Composites consisting of Al-Zn/Al2O3 have been synthesized using high energy mechanical milling. High energy ball milling increases the sintering rate of the composite powder due to increased diffusion rate. Owing to the finer microstructure, the hardness of the sintered composite produced by using the mechanically milled nanocomposite powder is significantly higher than that of the sintered composite produced by using the as-mixed powder. The mean crystallite size of the matrix has been determined to be 27 nm by Scherrer equation using X-ray diffraction data. The powders have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential thermal analysis (DTA). The effect of high-energy ball milling and subsequent annealing on a mixture of Al and ZnO has also been investigated. DTA result show that the reaction temperature of Al-ZnO decreases with the increase in the ball milling time.     

硬质相粒度对Ti（C,N）基金属陶瓷断裂韧性的影响

用压痕法测定了具有不同粒度硬质相的Ti(C,N)基金属陶瓷的断裂韧度,结果发现,当成分和制备工艺不变时,Ti(C,N)基金属陶瓷的断裂韧性随硬质相粒度的增大而减小,进一步分析表明,当Ti(C,N)颗粒较粗时,极易发生穿晶断裂,并且裂纹连续穿晶扩展时亦不会发生显著的偏转或分叉,金属陶瓷呈现较强的脆性断裂特征,而当Ti(C,N)颗粒较细时穿晶断裂几率大大减小,裂纹较易沿Ti(C,N)颗粒与粘结相的界面扩展,导致脆性断裂现象减少和裂纹偏转而增韧。产生上述现象的主要原因与Ti(C,N)晶体的结构有关,面心立方结构的Ti(C,N)晶体中可能存在多个潜在的滑移面和滑移系,裂纹从一个Ti(C,N)颗粒扩展至另一个Ti(C,N)颗粒时很容易形成取向有利。     

TiC/NiCrMoAlTi金属陶瓷的微观结构与力学性能

采用粉末冶金真空烧结方法制备了TiC/NiCrMoAlTi金属陶瓷.研究了Mo含量对TiC/NiCrAlTi金属陶瓷的微观结构与力学性能的影响.结果表明,在TiC/NiCrAlTi金属陶瓷中添加Mo后,在金属陶瓷的硬质相颗粒周围出现了典型的环形相,随着Mo含量的增加,环形相增多变厚,致使金属陶瓷的硬度线性增加,环形相的生成使金属陶瓷硬质相的颗粒细化、尖角钝化,从而提高了金属陶瓷的抗弯强度,当环形相过度发达时由于其本身较脆,金属陶瓷的抗弯强度降低,Mo含量为4%(质量分数)时抗弯强度达到最大值.     

Effect of Ni powder characteristics on the consolidation of ultrafine TiMoCN cermets by means of SPS and HIP technologies

Fully dense titanium carbonitride cermets have been consolidated from Ti(C,N)–Ni–Mo₂C–TiAl₃ powder mixtures either by spark plasma sintering or hot isostatic pressing techniques. Carbonyl Ni powders enhance the densification of the cermets produced by SPS (spark plasma sintering), a phenomenon likely related to a more efficient dissolution of Mo₂C additions and the possible precipitation of α″ phase. Both SPS and HIP (hot isostatic pressing) processes lead to materials with a bimodal Ti(C,N) grain size distribution containing a considerable fraction of nanometric grains. Unlike SPS, HIP induces significant graphite precipitation which could be explained by the destabilization of the carbonitride phase under high isostatic pressures at high temperature. Optimized compositions processed by SPS exhibit a combination of hardness and toughness close to the range covered by ultrafine WC–Co hardmetals of similar binder contents.