【作者】 赵铮；

【导师】 李晓杰；

【作者基本信息】 大连理工大学 ， 工程力学， 2007， 博士

【摘要】 颗粒增强铜基复合材料不但具有优异的导电、导热特性，而且还具有较高的强度、硬度和较好的耐磨性、耐热性，目前被用作电阻焊电极、氧枪喷嘴、集成电路引线框架、真空开关触头等。但颗粒增强铜基复合材料的制备工艺复杂、工艺成本较高，导致了材料的价格比较昂贵，影响了材料更广泛的应用。本文提出了一种新的制备工艺，该工艺设备简单、制备成本较低，能够获得优质廉价的颗粒增强铜基复合材料。主要包括三道工序：1)采用机械合金化法制备混合粉末。2)粉末预压后进行氢气还原烧结。3)采用直接爆炸压实方法制备块体材料。其中爆炸压实是整个制备过程中最重要的工序，爆炸压实又称爆炸烧结，是利用炸药爆轰产生的冲击波把金属或非金属粉末压实烧结成密实体的粉末成形工艺。爆炸压实具有高压、高温、瞬态的特点，是制取新型非平衡态材料、高温陶瓷材料等最富有潜力的新工艺。本文从理论、实验、数值模拟三个方面对爆炸压实法制备颗粒增强铜基复合材料进行了研究，主要得出了以下成果：1．以一种爆轰产物的近似状态方程为基础，结合爆轰波阵面上的参数关系，得出了一种形式简单的凝聚炸药爆炸产物P-V关系式。利用该式通过非线性拟合得出了JWL方程的六个参数。拟合得到的参数与实验获得的参数相比较，精确度较高，可以满足工程应用。2．提出了一种新的制备工艺，分为机械合金化法高能球磨、通氢还原烧结和爆炸压实三道工序。采用该工艺制得了Cu-aAl₂O₃与CuCr两种块体材料。材料的相对密度达到了98％以上，而且具有较高的硬度。通过对比多组实验结果，确定出了合适的工艺参数，即球磨20小时、通氢还原烧结0.5小时、炸药爆压为4GPa。3．采用LS-DYNA程序对直接法爆炸压实过程进行了数值模拟，总结了爆轰波及压实体内冲击波的传播规律。成功模拟出了马赫孔的形成过程，并对马赫孔的产生原因进行了详细论述，认为马赫孔的形成主要是因为轴心处的粉末与边缘粉末存在较大轴向速度差，产生了类似于“冲孔”效应的剪切变形，当爆速较高、爆压较大时剪切应力超过了粉末间的剪切强度极限，就会形成马赫孔。4．采用有限元法模拟了基体中的圆形孔隙和三角形孔隙的塌缩过程，计算出了射流侵彻速度及斜碰撞速度，总结出在较高的冲击压力下孔隙闭合时会形成爆炸焊接，并对爆炸焊接区域进行了划分。采用SPH无网格方法模拟了颗粒间的孔隙塌缩过程，观察到了射流侵彻现象，并得到了射流侵彻速度。通过对铜铬混合粉末的数值模拟，证明了双密度双硬度粉末爆炸压实前进行机械合金化是十分必要的。更多还原

【Abstract】 Particle reinforced copper matrix composites have not only excellent electric conductivity and heat conductivity but also high strength and hardness, well abrasion resistance and heat resistance, that have been used as electric resistance welding electrode, oxygen lance nozzle, IC lead frame, vacuum contact, etc. Existing preparation technology of particle reinforced copper matrix composites is very complex and costs very much, which lead to the materials’ price is so high that application is limited.In this paper, a new preparation technology is proposed, that with simple equipment and low cost. By the new preparation technology, high-quality and low-price particle reinforced copper matrix composites can be obtained. The new preparation technology includes three basic steps: 1) Preparing uniformly mixed powders by mechanical alloy method. 2) Sintering the advance compacted powders in hydrogen atmosphere. 3) Preparing bulk materials by direct explosive compaction method. Thereinto, explosive compaction is the most important process among all the preparation process. Explosive compaction is also known as explosive sintering, and it is a powder forming technology that using shock wave generated by explosion to compact metal or nonmetal powders. Explosive compaction method is noted for its high-pressure, high-temperature and instant property, and it is the greatest potential new technology to prepare new kind of nonequilibrium materials and high-temperature ceramics.The research on preparing particle reinforced copper matrix composites by explosive compaction in this paper includes three aspect contents: theory, experiment and numerical simulation. The featured research results include:1. A new P-V relationship of condensed explosive’s explosion products is obtained which form is very simple. Through the relationship we can nonlinear fit six parameters of JWL equation of state. Comparing fitted parameters with experimental parameters, it is found that fitted parameters are very accurate and can satisfy engineering application.2. A new preparation technics is proposed to manufacture particle reinforced copper matrix composites, which includes three processed: mechanical alloy, hydrogen sintering and explosive compaction. Cu-aAl₂O₃ and CuCr bulk materials are obtained by the new preparation technology. The relative density of two kinds of materials exceeds 98％, and their hardness is very high. Some appropriate technology parameters are confirmed, namely ball milling time is 20 hours, sintering time in hydrogen is 0.5 hour and explosion pressure is 4GPa through analyzing many groups experiment results.3. Research on numerical simulation of direct explosive compaction method is done by LS-DYNA program. The propagation rules of detonation wave and shock wave in compaction bulk are summarized. Mach hole is observed in numerical simulation and its formation reason is detailedly discussed. A conclusion is obtained that axial direction velocity difference between the powders in axes and edge create shear deformation such as punching hole, while shear stress is higher than shear strength limit of powders, then Mach hole will come into being in compaction bulk.4. The collapse process of circle and triangle pores in matrix bulk is simulated by finite element method. The velocity of jet penetration and oblique impact is calculated. Explosive welding will shape under high shock pressure during pores collapse, and explosive welding area is divided into three regions. The pores collapse process among particles is simulated by SPH Meshless method. Jet penetration phenomenon is observed and its velocity is obtained. Through the numerical simulation of CuCr powders, Mechanical alloy before double density and double hardness mixed particles explosive compaction is proved to be essential.更多还原