【作者】 王博；

【导师】 张凯锋； 王国峰；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2013， 博士

【摘要】 SiCp/2024Al复合材料具有高比强度、比模量，耐高温、耐磨损，良好的耐疲劳性能和断裂韧性、热膨胀系数小及尺寸稳定性好等特点，可适应航空航天等领域对工程结构减轻重量、提高性能的需求。但是由于SiC陶瓷颗粒的加入使得复合材料板材的塑性和韧性降低，极大地限制了SiCp/2024Al复合材料的应用和推广。为解决SiCp/2024Al复合材料二次加工困难的问题，本文利用脉冲电流通过金属板材产生焦耳热、电致塑性效应，研究了脉冲电流辅助拉深成形工艺。同时，采用加入Al-Cu-Ti粉末作为连接中间层，进行了SiCp/2024Al复合材料脉冲电流辅助瞬态液相（Transient liquid phase, TLP）扩散连接工艺的研究。针对脉冲电流作用于金属材料时，其电热物理特性的复杂性，本文进行了加热速率、加热温度、热传导及热扩散等脉冲电流加热特性的研究。结果表明采用铜/钢复合电极，在紫铜电极与坯料之间加入不锈钢保温片的方法，能够有效地减小坯料与电极间的热传导，提高板材坯料温度场分布的均匀性。同时，通过研究脉冲电流加热对SiCp/2024Al复合材料的拉伸性能及微裂纹损伤修复的影响，为脉冲电流辅助成形技术走向工程化做好充分的实验数据和理论准备。通过对脉冲电流辅助成形工艺的可行性分析，结合脉冲电流作用下SiCp/2024Al复合材料的电热物理特性，进行了脉冲电流辅助拉深成形工装设计及工艺参数的选择，并完成了SiCp/2024Al复合材料零件的拉深成形。成形的工件表面质量光滑、厚度均匀、无明显划伤和褶皱，圆角处无显微裂纹出现，尺寸精度达到±0.2mm。与传统的热成形工艺相比，脉冲电流辅助成形技术采用脉冲电流加热及板材拉深成形一体化设计，具有设备简单、加热速度快、热损失少及被加工材料氧化较小等特点。为了解决SiCp/2024Al复合材料焊接性较差，使用一般的连接方法都难于达到理想的效果，从而影响到部件的安全性和可靠性等问题，本文提出了脉冲电流辅助瞬态液相扩散连接技术，利用低压高强度脉冲电流通过连接界面与Al-Cu-Ti粉末中间层产生焦耳热、高温等离子体和电迁移等效应，实现对SiCp/2024Al复合材料板材的TLP扩散连接。通过对连接接头的微观组织及力学性能的分析结果显示，连接接头成份均匀、质量良好、原位生成的Al₃Ti等增强相能产生颗粒弥散强化，阻碍位错滑移，在连接时间为60min时，其剪切强度值大于154.1MPa，极大的提高接头的剪切强度。采用脉冲电流辅助TLP扩散连接技术，进行了SiCp/2024Al复合材料两层结构的连接，接头中间层与铝合金基体界面呈冶金态连接，未见有夹杂、偏聚及气孔等缺陷，Cu元素扩散至母材当中，形成了明显的扩散层，连接质量良好。铝基复合材料的多层结构主要取决于其连接接头的组织结构和力学性能，由于表面氧化膜和碳化硅颗粒偏聚的影响，造成了SiCp/2024Al复合材料的连接难以达到理想的效果，极大的制约了SiCp/2024Al复合材料板材多层结构的发展与应用。脉冲电流辅助TLP扩散连接技术的出现，为铝基复合材料多层结构的应用提供了可能，相信随着研究深入进行，作为一种高效、节能的绿色制造技术，脉冲电流辅助TLP扩散连接技术能够在铝基复合材料多层结构连接等方面有着越来越广泛的应用前景。更多还原

【Abstract】 SiCp/Al composites have been utilized in lightweight structures in the field ofairplanes and aerospace etc. because of their many wonderful properties, such asthe high specific strength and modulus, good high temperature and wear resistance,lower thermal expansion coefficient, stable geometric accuracy and so on. However,SiC particle in Al alloy matrix make the plasticity and ductility of SiCp/Alcomposites decreased, which restrain the application of SiCp/Al composites inindustry. In order to solve issues of the secondary material working, the hith-intensity pulse current to get through SiCp/Al composites sheet were applied, whichcan produce Joule effect and electroplastic effect. The feasibility of pulse currentauxiliary deep drawing and process parameters were investigated in this work. Inaddition, the pulse current auxiliary TLP diffusion bonding of SiCp/2024Alcomposites sheet were studied by using mixed slurry of Al-Cu-Ti powder interlayer.Based on much complexity of electric-thermal properties during pulse currentgetting through metal sheet, pulse current heating were studied in this work,including pulse heating velocity, heating temperature, thermal conductivities,thermal convection etc. The results show that the stainless steel （SUS304） withlower thermal conductivities and higher electric resistance was attempted to reducethe thermal transmission between sheet and copper electrode, which promoted thetemperature distribution. In addition, the effects of pulse current heating on tensileproperties and microcrack healing were studied to provide the experimental andtheoreticl supports for application of pulse current auxiliary forming technology inindustry.Take account of electric-thermal properties synthetically during pulse currentgetting through SiCp/2024Al sheet, the feasibility of pulse current auxiliaryforming were analysed and the forming die were designed. Through the choice andoptimization of process parameters, the workpiece of SiCp/2024Al composites weredeep drawn successfully. The workpiece exhibit good shape retention, surfacequality, and high geometric accuracy. Fluoroscopy measurements did not reveal anymicrocracks in the workpiece and the error in dimension was in the range of-0.2to0.2mm. Compaired to the traditional thermal forming process, pulse currentauxiliary forming technique integrate pulse current heating with deep drawing and have many advantage including simple setup, high heating rates, lower energy lostand lower oxidation.The traditional bonding technologies can not arrived to ideal joint because ofthe bad bonding properties of SiCp/2024Al composites, which have importanteffects on safety and reliability of joints. Therefore, pulse current auxiliary transientliquid phase （TLP） bonding technology were studied, which utilized hith-intensitypulse current to get through Al-Cu-Ti powder interlayer and achieve the bonding ofSiCp/2024Al composites. Joule heat effect, electromigration effect, SPS can beproduced during pulse current auxiliary TLP bonding process. The microstructureand mechanical properties of joints of SiCp/2024Al composites were analysed. Theresults show the dense joints exhibite the uniform composition, good bonding qulity.In addition, in situ formation of Al₃Ti intermetallic phase in joints can induce theparticle dispersion strengthening and hindering dislocation sliding, which canprovide the mechanical properties of joints.The double-sheet structures of SiCp/2024Al were fabricated using pulsecurrent auxiliary transient liquid phase diffusion bonding technology. The resultsexhibited the joints show the metallurgical bonding between powder interlayer andaluminum matrix composites, which have no flaws including impurities, SiCparticle congeries and pores. The diffusion layers of Cu and Al₃Ti intermetallicphase were formed to guarantee the good qulities of joint. The mutle-sheetstructures of SiCp/2024Al composites were depended on the microstructure andmechanical properties of joints, but the worse qulity of joints of SiCp/2024Alcomposites restrained the development and application of the multi-sheet structuresof SiCp/2024Al composites because of oxidation film and SiC particle congeries.Pulse current auxiliary transient liquid phase diffusion bonding technology can beapplied to bond SiCp/2024Al composites sheet and promote the application ofmulti-sheet structures of SiCp/2024Al composites. Pulse current auxiliary transientliquid phase diffusion bonding technology with high-efficiency and lower energylost can promote development and application of multi-sheet structures ofSiCp/2024Al composites in future.更多还原