【作者】 曹健；

【导师】 冯吉才；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2007， 博士

【摘要】 金属与陶瓷的连接一直是连接领域研究的热点和难点问题之一,常规的连接方法很难满足二者的连接要求。本文针对TiAl与TiC金属陶瓷,开展了自蔓延反应辅助扩散连接问题的研究。采用试验研究和理论分析相结合的方式,进行了连接中间层的成分优化,确定了采用粉末中间层时的接头极限尺寸,并对采用这种特殊连接方法时的界面结构和组织演化进行了系统的分析,揭示了连接工艺参数对接头性能及界面反应的作用规律。中间层优化设计是自蔓延反应辅助扩散连接最根本的工作,主要包括中间层组元选择与成分确定两个方面。针对粉末体系与预热温度对绝热温度的影响进行计算,确定了适合TiAl与TiC金属陶瓷连接的粉末中间层成分为Ti（17-47%）、Al（13-25%）、C（4-12%）、Ni（28-54%）（wt.%）。解明了Ti-Al-C-Ni四元体系的反应机制,整体自蔓延反应首先由Al-Ni系反应引燃,而后引发Ti-C系反应。基于对燃烧速度的试验测试和理论分析,求取了体系的表观激活能,并利用反应产物测试对反应机理分析进行了验证。冷壁效应是中间层自蔓延反应熄灭的主要原因,利用连接过程传热分析确定了中间层自蔓延反应熄灭的临界燃烧温度与速度,在考虑极限热损失情况下,确定了中间层与两侧母材的极限长度。采用Ti-Al-C-Ni粉末中间层进行了TiAl与TiC金属陶瓷的自蔓延反应辅助扩散连接,典型的接头界面层结构为:TiAl/TiAl3/（Al-Ni）+TiC/Ni-rich/ TiC-Ni。分析了采用粉末中间层时工艺参数对于连接过程的影响,发现电磁场辅助连接接头比电场辅助连接接头的致密度低,但是采用电场辅助连接时在接头处容易产生裂纹。对粉末粒度、连接压力、后热处理温度和时间等参数的作用效果进行了分析,最终确定本试验条件下,合适的连接工艺参数为500MPa的预制坯压力、40MPa的连接压力、1050℃的连接温度、60min的保温时间,电场辅助连接,此时采用等摩尔比的TiAlCNi中间层能获得抗拉强度为128.1MPa的连接接头,断口分析结果表明中间层反应产物致密度是影响连接质量的主要原因。研究了自蔓延反应辅助钎焊方法的界面结构和连接机理,基于体系热分析及反应产物孔隙率分析确定所需钎料量,针对TiAl自身及TiAl与TiC金属陶瓷的连接进行了试验。该方法利用中间层反应放热熔化钎料,液态钎料填充到中间层反应产物的孔隙中从而能明显的提高连接质量,可以将高温钎料的钎焊加热温度降至体系自蔓延反应引燃温度,同时提高接头的使用温度,该方向的深入研究对于自蔓延辅助连接技术的实用化具有重要意义。采用Al/Ni多层膜能够实现TiAl与TiC金属陶瓷的自蔓延反应辅助扩散连接。连接接头中没有发现孔隙,典型的接头界面层结构为:TiAl/ TiAl+Ti₃Al+NiAl₂Ti/NiAl₂Ti/Ni₂AlTi/Ni₃（AlTi）/AlNi/AlNi₃/TiC-Ni。纳米压痕和强度测试结果表明,在TiC金属陶瓷侧出现的AlNi₃层是影响连接质量的主要原因。对纳米多层膜与微米多层膜的反应性能、反应产物以及连接接头界面结构进行了对比,发现采用纳米多层膜能够获得更理想的连接质量。研究了采用纳米多层膜连接TiAl与TiC金属陶瓷时的温度分布,定量描述了中间层反应对于两侧母材的热作用,为多层膜在异种材料连接领域的实际应用提供了理论基础。更多还原

【Abstract】 The joining between ceramic and metal always serves as one of the hot and difficult issues in the joining fields. It is difficult for the traditional joining method to achieve the sound joining between ceramic and metal. The investigation about self-propagating reaction assisted diffusion bonding (SADF) of TiAl to TiC cermt was carried out in this study. The experimental method was combined with theoretical method. The optimal design of the interlayer was performed and the analysis of the critical dimension in the joint for the powder interlayer was completed. The interfacial microstructure and microstructural evolution for this special joining method was systematically analyzed. The effect of the parameters on the joining quality and interfacial reaction was investigated.The optimal design of the interlayer, which consists of the selection of the interlayer element and interlayer composition, is the basic target for the SADF. The effect of the interlayer composition and preheating temperature on the adiabatic temperature was studied. The powder interlayer composition for joining of TiAl to TiC cermet was determined as Ti(17-47%),Al(13-25%),C(4-12%),Ni(28-54%)(wt.%). The analysis for the Ti-Al-C-Ni system showed that Ti-C reaction was ignited by Al-Ni reaction. The apparent activation energy was calculated by the measurement and analysis of combustion velocity. The analysis of reaction products confirmed the reaction mechanism. The quenching of self-propagating reaction in the interlayer was generated by the cold plate effect. The critical combustion temperature and velocity were determined using the apparent activation energy. The critical dimension of interlayer and substrate was determined considering the critical heat loss.The SADF of TiAl to TiC cermet was achieved using Ti-Al-C-Ni powder interlayer. The typical microstructure was: TiAl/TiAl3/(Al-Ni)+TiC/Ni-rich/TiC-Ni. The effect of the parameters on the joining process using powder interlayer was studied. The density of joint using assisted electromagnetic field was lower than using assisted electronic field. However, the crack tended to generate in the joint with assisted electronic field. The effect of powder granularity, joining pressure and post-heating treatment was analyzed. The optimal joining parameter was 500MPa pressure for compact, 40MPa joining pressure, 1050℃joining temperature, 60min holding time and assisted electronic field. The tensile strength of 128.1MPa was achieved with equal atomic percent of TiAlCNi interlayer. The fracture analysis showed that the main reason for the poor joining properties was the low density in the products.The microstructure and joining mechanism for self-propagating reaction assisted brazing was investigated. The content of filler metal was determined considering the thermal and porosity analysis in the products. The joining experiment for TiAl to TiC cermet was carried out. The filler metal was molten by the heat released in the interlayer. The molten filler metal filled in the porosity of reaction products and the joining properties was increased. The heating temperature of high-temperature filler metal was decreased to the ignited temperature of the self-propagating reaction in the interlayer. The joint could be applied in high-temperature condition. The further investigation was helpful for the utilization of self-propagating assisted joining.The SADF of TiAl to TiC cermet was accomplished using Al/Ni multilayer. No porosity was observed in the joint using Al/Ni multilayer. The typical microstructure was: TiAl/ TiAl+Ti3Al+NiAl2Ti /NiAl2Ti/Ni2AlTi/Ni3(AlTi)/AlNi/ AlNi3/TiC-Ni. The nanoindentation and strength test shows that the AlNi3 layer was the main reason affected the joining properties. The reaction characteristic, reaction products and interfacial microstructure using nano multilayer was compared with using micron multilayer. The better joining quality was achieved using nano multilayer. The temperature distribution for joining of TiAl to TiC cermet using nano multilayer was investigated. The investigation about quantitative heat effect of interlayer on the substrate generated the theoretical basement for the wide application of the multilayer in the joining fields.更多还原