WC弥散强化铜的制备及其性能研究

【作者】 张立勇；

【导师】 王孟君；

【作者基本信息】 中南大学 ， 材料加工工程， 2004， 硕士

【摘要】 弥散强化铜具有良好的导电性和高温性能等，广泛应用于汽车、电子等行业。本文就新型弥散强化铜的开发作了研究。 采用高能球磨技术制备了不同含量的WC／Cu复合粉末，利用SEM和XRD技术对球磨后粉末的形貌、粒度和物相成分等作了分析，据此确定最佳的球磨工艺。其次以此工艺为基础制备复合粉末，等静压成型，然后分别研究了不同烧结工艺对材料致密度、硬度、强度、延伸率和导电性等性能的影响，同时结合显微分析手段讨论了烧结工艺对材料显微结构的影响。 结果表明，通过高能球磨可获得分布均匀的复合粉末；随球磨时间延长，粉末粒径首先快速下降，而后趋于平缓，并且WC含量高的复合粉末细化进程较含量低的快；在本文条件下认为球磨24h为佳；整个球磨过程未发生相变，球磨使得粉末发生晶格畸变，球磨时间越长畸变越大。 烧结动力主要是粉末表面能和粉末变形积累的晶格畸变能；烧结主要受第二相含量、烧结温度和保温时间等因素影响，第二相含量越低，烧结温度越高，保温时间越长则烧结越充分；Cu-4％WC的最佳烧结工艺为1000℃／2.5h；WC含量高的材料中有较多孔隙和偏聚。 相同压力下第二相含量越高，压坯密度越小；烧结可少量地提高致密度；材料的性能取决于烧结状况和微观组织等，烧结越充分，致密度越高，组织越均匀，则性能越好；第二相、孔隙度和固溶杂质均会损害材料的导电性，但第二相含量和孔隙度的影响较杂质影响小得多；综合比较材料的组织和性能，Cu-4％WC在1000℃下烧结2.5h的性能较好；高温变形后材料未发生明显的再结晶。更多还原

【Abstract】 Dispersion strengthened copper (DSC) is widely used in automobile and electronic industry because of its excellent conductivity and high-temperature property. Present work is an attempt to develop a new kind of DSC.WC/Cu composite powders with different WC content milled for a different time were examined with SEM and XRD technique to find out the optimum milling time in terms of morphology, mean powder size and phase composition. On the basis of the result, composite powders were prepared and compacted by cold isostatic press (CIP). Compacted samples were sintered under different conditions to investigate the effect of processing parameters on materials properties (density, hardness, tensile stress and conductivity) after sintering.As a result, composite powders with uniform particle distribution and refined microstructure could be prepared by means of high energy milling, and prolonged milling time resulted in smaller powder size. Powder containing more WC particles refined faster than that with a low content. 24h’ milling seemed better overall. No phase transformation occurred during milling. Milling caused lattice strain of copper powders.Driving force for sintering were powder surface energy and stored energy caused by deformation. Sintering was affected by particles content, sintering temperature and preserving time. Generally, more particles content, higher sintering temperature and longer time led to a more complete sintering and improved microstructure. Optimum sintering differed depending on particle content, and for Cu-4%WC the best sintering was at 1000℃ for 2.5h. In material with a high WC content many pores and particle agglomerations were observed.Under the same compaction pressure, green density of sample with a low WC content was higher than that with a high content. Sintering could improve density slightly. Properties of material were determined mainly by the microstructure. The higher the density was, the more completely the sintering progressed, the more uniform the microstructure was, the better properties the material exhibited. Increase in particle content, porosity and solved impurity resulted in decreased electrical conductivity. But the effect that particle content and porosity had on the conductivity was much minor compared with the impurity. Comparison between all materials showed Cu-4%WC sintered at 1000@ for 2.5h had the best overall properties. No obvious recrystallization was observed in materials deformed at high temperatures.更多还原