新型纳米ZrC/Cu点焊电极材料的原位合成机制、组织及性能

Spot welding technology has been widely used in the manufacturing, such as automobile, instrument and aircraf, etc. It is easy for Cu alloy electrodes to become invalid because its service temperature and pressure exceed 900 K and 0.5 GPa, respectively. As a result, the production efficiency and welding quality were lowered. One of the solutions to this problem is to develop in situ nano-sized pariculates reinforced Cu martix composites. ZrC possesses excellent multifunctional properties, especially superior electrical conductivity. Therefore, it is promised that in-situ nano-sized ZrC/Cu composites possess high strengh and excent electrical conductivity. On the basis of previous studies, this subject would select Cu-Zr-C system as the reasearch object and prepare in-situ nano-sized ZrC/Cu composites through direct reaction technology. It is expect to reveal the indivicual and common formation mechanism inside and outside Cu liquid during combustion reaction process through comparative researchs of the formation and conversion of phases and the microstructure evlution behaviors of Cu-Zr-C system in glove box and Cu liquid during combustion synthesis process. At the same time, we hope to verify the reaction kinetics characteristics and make clear the mechanism of Cu-Zr intermediate reaction on the growth behaviors of ZrC particles through the changes of reaction parameters, and establish the realation model between the microstructure and properties of ZrC/Cu composites as well. The implementation of this project is expected to realize the active control of propeties by the design and optimizing of microstructures, and offer effective theoretical guidance for developing novel high-strength and high-conductivity nano-sized partilces reinforced Cu matrix spot welding elctrode material.

点焊广泛应用于汽车、仪表及航空等制造行业，因服役时常承受900 K和0.5 GPa以上温度与压强，铜合金电极易失效而降低生产效率和焊点质量。解决该问题的有效途径之一是发展原位纳米颗粒增强Cu基复合材料。ZrC综合性能良好，尤其导电性突出，故内生纳米ZrC/Cu可望兼具高强高导性能。在前期工作基础上，本项目拟以Cu-Zr-C体系为研究对象，通过接触反应技术原位合成ZrC/Cu复合材料，开展Cu-Zr-C压坯在手套箱和铜液内燃烧合成过程中相形成、相转变与组织演化的比较研究，揭示铜液内、外燃烧合成反应机制的个性与共性规律。同时，通过改变反应过程参量，明晰体系的反应动力学特性，揭示Cu-Zr中间反应对ZrC生长行为的作用机制，并构建ZrC/Cu组织与性能的关系模型。本项目的实施，可望通过微观组织的设计与优化，实现性能的主动调控，为开发新型高强高导纳米颗粒增强Cu点焊电极材料提供理论指导。

铜导电性好，但强硬度低，解决方法之一是发展原位纳米颗粒增强Cu基复合材料。本项目设计了Cu-Zr-C/B4C新型体系，通过研究铜液内、外（手套箱中）燃烧合成反应机制、反应动力学特性及复合材料的组织性能，为开发新型高强高导纳米颗粒增强Cu点焊电极材料奠定一定理论基础。. 揭示Cu-Zr-C/B4C体系铜熔体内、外的燃烧合成机理均为溶解反应析出机制，即Cu与Zr先经固态扩散反应生成CuxZry化合物，随后转化为Cu-Zr液体，当C或B4C颗粒扩散溶入Cu-Zr液相中形成Cu-Zr-C或Cu-Zr-B-C多元液相，最后ZrC或ZrC-ZrB2从饱和液体中析出。. 揭示Cu-Zr-C/B4C体系动力学因素(Cu含量，C或B4C粒度，Cu粉粒径，C/Zr比)对燃烧合成反应过程、反应行为和产物的影响机制，阐明Cu-Zr中间反应与ZrC或ZrC-ZrB2尺度的内在联系。随Cu含量的提高，Cu-Zr固固反应生成的CuxZry中间相增多，Cu-Zr液相形成变易，ZrC或ZrC-ZrB2的合成温度降低，引燃时间(Tig)先减后增，燃烧反应温度(Tc)、燃烧波速(v)及产物中陶瓷的粒径减小。增大C或B4C粒度，Cu-Zr固态合成的CuxZry化合物增多，转为的Cu-Zr液相体积分数提高，C或B4C向Cu-Zr熔体的扩散溶解速度减慢，陶瓷的合成温度降低，Tig延长，Tc、v及ZrC或ZrC-ZrB2的尺度减小。增大Cu粉粒径将提高Cu-Zr固固反应温度，减少合成的CuxZry中间相，但在Cu-Zr液相形成之后，Cu、Zr等固相向液体的快速溶入消除了Cu粉尺度引起的差异，陶瓷的形成温度无明显变化，Tig延长，Tc、v及陶瓷颗粒尺寸变化不大。Cu-Zr-C体系中C/Zr比的增加不影响CuxZry中间相的固态合成，但会改变CuxZry、C等向Cu-Zr液相的溶入及ZrC的形成温度，Tig先减短后延长，Tc、v和ZrC的尺寸先增后减。. 通过外加燃烧合成纳米ZrC或ZrC-ZrB2颗粒搅拌铸造法与铜液内原位自生法两条路径，成功制备出纳米ZrC或ZrC-ZrB2弥散强化Cu基复合材料，可在保持Cu优良导电性的同时显著提高其机械性能。采用原位内生法，随Cu-Zr-C/B4C粉末中Cu含量、C或B4C粒度的增加，复合材料中陶瓷颗粒的尺寸由约100 nm减小到50 nm。