Mo-Cu复合材料的烧结机制研究

Mo-Cu复合材料具有良好的导热导电性能和低的膨胀系数,是目前国内外受到广泛关注和研究的一种新型材料.研究了Mo-Cu复合材料的固相和液相烧结工艺,分析了其烧结机理.结果表明:固相烧结试样的组织疏松,粉末颗粒间存在着大量的不规则孔隙,致密化程度较低.液相烧结Mo-Cu复合材料的整个过程分为颗粒重排、 溶解和再析出及Mo颗粒的固相烧结3个界限不十分明显的阶段.     

纳米Mo-Cu超饱和固溶体粉的结构特征及其烧结机制

采用溶胶-喷雾干燥-煅烧-氢还原方法制备了纳米Mo-Cu复合粉末。综合利用XRD、TEM和EDX等检测方法对该Mo-Cu复合粉末的相结构特征和粉末体的烧结机制进行了分析。结果说明:纳米Mo-Cu复合粉末由Mo(Cu)和Cu(Mo)超饱和固溶体组成,但该Mo(Cu)和Cu(Mo)超饱和固溶体呈不稳定状态,随烧结温度升高和保温时间延长,固相Mo(Cu)中析出的Cu逐渐溶解于液相Cu(Mo)中,而液相Cu(Mo)中的Mo逐渐析出沉积在固相Mo(Cu)颗粒上,此过程促进了烧结体致密化。     

机械热化学法制备的Mo-Cu复合粉末及其性能

钼酸铵热解氧化物与铜粉经过球磨混合后,在H2气氛下进行共还原,制得Mo-30Cu复合粉末,利用X射线衍射、SEM等测试分析手段对复合粉末进行表征,研究粉末的压制行为和烧结性能,并研究烧结温度对Mo-Cu合金的致密度、热导率和电导率的影响。结果表明:采用机械-热化学法可以制备出颗粒均匀的Mo-Cu复合粉末,该粉末具有良好的压制性;随烧结温度的升高,Mo-Cu合金的致密度、热导率和电导率提高,经1 280℃烧结后,合金的致密度可达99%以上,显微组织分布均匀,合金的热导率最高达到196.5(W.m-1.K-1),电导率达50.5 IACS。     

溶胶-凝胶法制备超细Mo-Cu粉末及性能表征

以七钼酸铵和硝酸铜为原料通过溶胶-凝胶法制备Cu含量(质量分数)为20%的超细Mo-Cu复合粉末,再在1050～1200℃下烧结粉末压坯制得Mo-Cu复合材料;通过热重分析(DTA-TG)、X-ray衍射分析(XRD)和透射电镜(TEM)等分别对干凝胶煅烧前后的粉体以及还原后所得Mo-Cu复合粉末进行表征,通过扫描电镜观察Mo-Cu烧结体的显微组织,并对其密度、物理和力学性能进行测定,探索制备高致密、高性能Mo-Cu复合材料新工艺.结果表明:通过溶胶-凝胶法可以制得平均粒度为150nm、组成均匀的Mo-Cu超细粉末,该粉末具有良好的烧结性能,其成形压坯在1200℃下于H2气氛中烧结90 min后,相对密度可达99.78%,烧结体的抗弯强度和维氏硬度分别为988 MPa和HV 227,电导率和导热系数分别为42.56%IACS和157 W/(m·K),室温至450℃的热膨胀系数在6.7×10-6～7.6×10-6K-1之间.     

球磨时间对W-30Cu复合粉末中W晶粒度及烧结致密化行为的影响

研究了高能球磨时间对W-30Cu复合粉末晶粒度及烧结行为的影响.结果表明,当球磨时间从16h提高到33h时,复合粉的晶粒度由25nm减小到10nm,并发生机械合金化现象;在温度为1275℃烧结60min,经18h高能球磨的复合粉末烧结就可以达到全致密.研究还发现,高能球磨W-30Cu复合粉末具有较好的热稳定性,经950℃退火处理,晶粒尺寸没有发生异常长大现象;经烧结材料的硬度明显高于普通的W-30Cu复合材料.经1 275℃烧结30 min后合金其晶粒尺寸在300～550 nm.     

高能球磨-放电等离子烧结法制备双晶分布钛

以平均粒径约150μm的球形钛粉为原料,采用高能球磨结合放电等离子烧结技术制备由双尺度晶粒组成的高致密纯钛块体材料,研究高能球磨过程中钛粉的形貌、尺寸及显微组织的变化,分析球磨钛粉放电等离子烧结时的致密化行为和显微组织的演变规律,测试烧结钛块体材料的室温压缩性能。结果表明:钛粉在球磨初期发生剧烈的塑性变形并相互焊合,形成层片状团聚粉末。球磨10 h时,钛粉的部分晶粒细化至40~100 nm。放电等离子烧结过程中,随烧结温度升高和烧结时间延长,烧结钛的密度逐渐增大。在烧结温度为800℃、保温时间为4 min、烧结压力为50 MPa的条件下,烧结钛的密度达到4.489 g/cm3,接近全致密,其显微组织由双尺度的等轴晶组成,细晶区晶粒尺寸为1~2μm,粗晶区晶粒尺寸为5~20μm,二者呈层状交替分布;该试样在室温压缩条件下的综合力学性能与铸锻Ti-6Al-4V合金相当。     

M42高速钢粉末球磨工艺优化及其SPS烧结

利用高能球磨法制备了不同粒度的M42高速钢粉末,并对其进行了放电等离子烧结(SPS)。测试了粉末粒度分布,观察了粉末及其烧结试样的形貌,探讨了高能球磨M42高速钢粉体的球磨行为特征及烧结试样的显微组织与性能。结果表明:在球料比7∶1下,随球磨时间增加,粉末细化速率先快后慢,48h后趋于平缓,且粉末的团聚不断加剧;球磨48h的粉末经在温度970℃、压力70MPa下保持10min SPS烧结的M42粉末高速钢相对密度为98.99%,热处理硬度为67.4HRC;随粉末粒度的减小,其碳化物更加细小、均匀,由于粉末的团聚化,其相对密度不断降低,而粒度对硬度的影响不大。     

电子封接用钼铜材料的制备

通过扫描电镜、透射电镜及X射线衍射等对Mo-Cu复合粉末的粉末形貌、合金化程度及烧结后合金组织结构进行分析,研究了高能球磨后Mo-Cu材料的显微组织及其与陶瓷热膨胀性能匹配的关系。结果表明,采用高能球磨机械合金化和氢气气氛烧结工艺制备的Mo-Cu复合材料,相对密度在98%以上,在室温至700℃热膨胀系数与陶瓷差值在8%。     

细晶钨铜复合材料制备工艺的研究

将W-20Cu混合粉末在行星式高能球磨机中机械合金化(MA),经过一定时间球磨后可以得到W晶块尺寸为30 nm左右的纳米粉末;采用XRD分析了粉末晶粒尺寸,测定了粉末的粒度、比表面、松装密度和振实密度等性能;研究了MA W-Cu20粉末烧结后的显微组织。研究结果表明,球磨后粉末在1 200～1 300℃时烧结即可达到近全致密,相对密度在99.5％以上,拉伸强度达到780MPa以上,延伸率大于3.5％,钨晶粒尺寸在1～2 μm左右。     

纤维状WC晶粒硬质合金的制备

以高能球磨方法处理制备的纳米晶复合粉末为原料，通过真空烧结制备硬质合金块体，研究该纳米晶复合粉末的烧结致密化行为和显微结构特征。结果表明：该纳米晶粉末的烧结致密化可依烧结温度从低至高分为、3个阶段，而在高于1250℃的液相烧结阶段，将温度提高至1375℃烧结30min，可获得密度为14．46g／cm^3、烧结收缩率为27．2％的致密硬质合金。此时，WC晶粒呈纤维状，随机分布在烧结体中，其长度约为1．2μm，径向尺寸约为100nm；采用高能球磨处理工艺可以获得原位生成的纤维状WC晶粒增强的硬质合金。     

Role of solid-state skeletal sintering during processing of Mo-Cu composites

Mo-Cu composites with Mo contents up to 85 wt pct can be processed by either infiltration of a presintered Mo skeleton with liquid Cu or by liquid-phase sintering of mixed Mo and Cu powders. For both cases, the effects of particle size, sintering temperature, and sintering time on densification and microstructural evolution are compared. The effects of transition metal additions on the densification of Mo-Cu are also investigated. The liquid-phase sintering densification rate of Mo-Cu is much slower than in traditional liquid-phase sintering and is similar to the solid-state densification rate of elemental Mo. Furthermore, the poor densification behavior and absence of slumping for compositions up to 50 vol pct Cu indicate that the high dihedral angle of the Mo-Cu system stabilizes the formation of a rigid Mo skeleton during liquid-phase sintering. Results from a computer simulation that takes into account mass transport via both solid-state and liquid-phase mechanisms show that the solubility of Mo in Cu is sufficient for rapid densification, but confirm that the sintering behavior of Mo-20 vol pct Cu is best described by solid-state skeletal sintering. In this case, the liquid phase promotes microstructural coarsening by solution reprecipitation but contributes little to densification because of the rigid Mo skeleton.     

Microstructures of Sintered Mo-Cu Alloys with Mechanically Activated Powder

Mechanical activation and liquid phase sintering were used to manufacture high performance Mo-Cu alloy and develop new processes. The microstructures and properties of the alloy were investigated. The experimental results showed that: (1) the ball milled Mo/Cu powder has lamellar structure, (2) the microstructures of the sintered Mo-Cu alloy were homogenous compound structures of adhesive phase Cu linking Mo grains, (3) Mo grains frequently strung or ga thered in Cu phase, and (4) the full densities of Mo-Cu alloy was achieved through sintering and special densification process. As a result, the properties of the alloy are good enough to satisfy various requirements.     

Effect of liquid phase on the densification of tungsten-copper and molybdenum-copper pseudoalloys in sintering

The paper examines how the amount of the liquid phase influences the densification of loose W-Cu and Mo-Cu powder mixtures in liquid-phase sintering at 1200°C, with the content of the low-melting component ranging from 20 to 90 wt.%. It is observed that the density grows continuously with increasing amount of the liquid phase in both W-Cu and Mo-Cu systems. It is shown that samples sintered with a great amount of the liquid phase in the W-Cu and Mo-Cu systems retain their shape.     

球磨方式对TiC/316L复合粉末压缩性及烧结行为的影响

应用双对数压制方程和相关烧结模型,分析和探讨不同球磨方式对TiC/316L复合粉末的压制特性及烧结行为的影响,并采用扫描电镜观察复合粉末的形貌。结果表明,采用湿磨方式获得的复合粉末,其破碎程度不够,很多316L不锈钢颗粒特别是颗粒较小的不锈钢颗粒变形不大,仍然呈球形,不利于其后续的压制和烧结;采用直接干磨获得的复合粉末,其表面新鲜断裂面多,粉末表面活性大,有利于粉末的烧结致密化,但其加工硬化明显,压制成形性能较差;与其他球磨方式相比,采用先干磨再湿磨的球磨方式获得的复合粉末不仅具有较好的成形性能,而且粉末烧结激活能低,以该粉末为原料可以获得较高相对密度的烧结体。     

新型低膨胀Mo-Cu合金电子封接材料研究

本试验研究了添加活化元素Ni对Mo-Cu合金的相对密度、烧结性能、热导率、电导率、热膨胀系数及组织的影响.研究结果表明:在Mo-Cu合金中加入Ni能降低合金烧结的致密化温度,促进烧结的进行.但Ni的加入降低了合金的导电和导热性能,并且使合金的组织变得粗大,75Mo-20Cu-5Ni的导热系数和95%Al2O3,陶瓷非常匹配,可被用作与其封接的合金.     

甘氨酸硝酸盐法制备超细Mo-Cu粉末及烧结

以四水合钼酸铵（（NH4）6Mo7O24·4H2O）、硝酸铜（Cu（NO3）2·3H2O）、甘氨酸和乙二胺为原料采用甘氨酸硝酸盐法（GNP）制备前驱体粉末,经过700℃氢气还原2 h得到Mo-Cu 复合粉末,经压制后进行真空烧结,研究不同烧结温度对Mo-Cu 烧结体性能的影响.结果表明：甘氨酸-硝酸盐法（GNP）制备的超细Mo-Cu 复合粉末形状规则、大小均匀、钼铜两相弥散分布,颗粒大小平均为50~80 nm.在950~1250℃范围内,随着烧结温度的升高,烧结体的硬度增大,致密度、电导率和热导率在1150℃达到最大值.     

Study on Agglomeration and Densification Behaviors of Gadolinium-Doped Ceria Ceramics

By synthesizing reactive powders via a self-sustaining combustion synthesis, the glycine-nitrate process, the gadolinium-doped celia （GDC） with the chemical formula Ce0.8Gd0.2O1.9 was prepared. The resultant powders were dispersed with the terpineol as the dispersant through different methods such as ball milling and high-shear dispersing. Coagulation factor （CF） was used to mark the degree of agglomeration on the nano-scale GDC in this work. The effect of agglomeration on the densification behavior at different sintering temperatures was investigated. The studies indicated that agglomeration retarded the densification at the sintering stage. The powders with better dispersion exhibited a higher sintered density at the same temperature. After effective dispersion treatment, GDC could be fully densified at the sintering temperature of 1300 ℃. The densification temperature was significantly lower than those reported previously. The high sintering kinetics of the ceramics was obtained based on the agglomeration control.     

包裹型SiO2/Al复合粉体的制备及烧结性能研究

为了克服金属陶瓷两相分布不均、界面不润湿和难以烧结致密等难题,采用球磨技术将增强相均匀包裹在基体材料表面,研究包裹型SiO₂/Al复合粉体的球磨制备工艺及其烧结性能,提高金属陶瓷的综合性能。结果表明,随着球磨时间的延长,SiO₂/Al复合粉体的比表面积先增大后减小,球磨6 h获得的复合粉体比表面积最大,达到8.1 m2·g?1。随着球料比的增大,SiO₂/Al复合粉体的比表面积先增大后减小,说明SiO₂包裹在Al粉表面的量呈现先增多再减少的趋势。随着球磨转速的增大,SiO₂/Al复合粉体比表面积先增大后减小。随着烧结温度的提高,SiO₂/Al金属陶瓷表面硬度先增高后降低,在烧结温度为900 ℃时,SiO₂/Al金属陶瓷的表面硬度达到最高。球磨时间为6 h,球料比为2:1,球磨转速为360 r·min?1,烧结温度900 ℃可以获得性能较佳的SiO₂/Al金属陶瓷。     

Fast Sintering of Nanocrystalline Copper

The behavior of nanocrystalline (nc) copper specimens obtained by high energy ball milling (HEBM) and electromagnetic field-assisted sintering under stress and mechanical compression is explored. High yield stress values combined with plastic behavior are observed. The basic densification mechanisms involved in the production process and the peculiar action on the dislocation network are discussed.     

球磨工艺对Al2O3/Mo复合材料组织的影响

针对原位自生Al2O3增强钼基复合材料晶粒较大的问题,采用溶胶-凝胶与高能球磨相结合的方法细化复合材料晶粒,并利用SEM、XRD对不同球磨工艺所制备Al2O3/Mo复合粉末及复合材料的组织进行了观察和分析。结果表明:随着球磨时间的延长,Al2O3/Mo复合粉末颗粒由球状变为层片状再成为细小的球状,颗粒大小由约1.5μm细化为约500nm,其中的钼晶粒不断细化;高球料比所得粉末的分散性和破碎细化程度较好;转速提高使得粉末颗粒的尺寸均匀程度降低,且伴有结块现象,不利于粉末的细化。在球料比5∶1、转速300r/min、球磨时间60h条件下获得的复合粉末,经压坯烧结可制备出Al2O3颗粒为纳米级的钼基复合材料。