氧化铝与镍铝合金表面生长晶须及钎焊接头组织与性能

发布时间：2018-03-16 02:09

本文选题：Al_2O_3陶瓷　切入点：Ni　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：Al_2O_3陶瓷具有强度高、耐高温、电绝缘性好等优良特性,广泛的应用于真空电器件中。然而随着产品性能的逐渐提高,极端条件下局部高温导致真空器件中与Al_2O_3陶瓷连接的不锈钢无法满足使用要求,严重影响产品的可靠性,若使用轻质高强耐高温的Ni Al合金替代不锈钢则可以全面提高产品性能。常规陶瓷/金属钎焊接头存在高温性能差,残余应力大等问题,为此本文提出在Al_2O_3陶瓷和Ni Al合金表面外延生长晶须,利用晶须生长直接连接Al_2O_3陶瓷以获得具有良好高温性能的接头,并采用钎焊方法对表面生长晶须的Al_2O_3陶瓷(简称Al_2O_3(W))自身及其与表面生长晶须的Ni Al合金(简称Ni Al(W))进行连接,通过基体表面晶须的反应调控形成复合焊缝区,从而对钎焊接头起到强化作用。分别以B_2O_3、H3BO3和B_2O_3+生长助剂为原料在Al_2O_3陶瓷和Ni Al合金表面生长晶须,利用SEM分析表征所得晶须形貌,研究了原料成分和生长工艺对晶须形貌的影响规律,并利用XRD和TEM分析了晶须成分、晶体结构及生长特性,探讨了晶须生长机理。结果表明,以B_2O_3为原料在950℃/4h工艺下可以获得分布均匀、结晶度良好的晶须,过高生长温度或过长保温时间均不利于晶须维持良好的一维形态;以H3BO3为原料所获得晶须形貌与以B_2O_3为原料时类似;添加Na Cl为生长助剂时,所得晶须粗大,根部缺陷多,且生长方向与陶瓷表面夹角较小;添加K2SO4作生长助剂时,仅能在1100℃/2h工艺下获得结晶度相对良好的晶须,但生长方向与陶瓷表面夹角较小;添加Mn O2作生长助剂时所得晶须尺寸相对较小。950℃所得晶须为正交结构Al4B2O9相,1050℃以上获得的晶须为正交结构Al18B4O33相,晶须在陶瓷表面为外延生长,Al_2O_3的(101—0)晶面与Al4B2O9的(220)晶面间晶格错配度仅为0.03%,晶须生长过程符合S-L-S自催化机理。基于Al_2O_3陶瓷表面生长晶须的研究结果,以B_2O_3为原料在Ni Al合金表面生长了硼酸盐晶须。在950℃/4h条件下获得了表面光滑、分布均匀的Al4B2O9晶须,1050℃/4h条件下除Al4B2O9外还发现了Ni3(BO3)2。随后,以纯Ni为基体对Ni3(BO3)2晶须的晶体结构和生长特性进行了详细分析。利用表面生长晶须对Al_2O_3陶瓷进行了直接连接,研究了中间层成分及连接工艺参数对所得接头组织形貌及高温强度的影响,分析了接头的连接机理。以纯B_2O_3为中间层在较低工艺参数下所得接头中晶须尺寸小,有B_2O_3残留。随着连接温度升高或保温时间延长,能贯穿焊缝生长对陶瓷实现直接连接的晶须数量增多,接头强度随之升高,1100℃/4h条件下所得接头800℃高温抗弯强度最高(27MPa),断裂发生在晶须内部。过高的连接温度或较长保温时间不利于接头中硼酸铝以一维形态生长或保留。当在B_2O_3中添加K2SO4或Mn O2时,所得接头中晶须数量大幅度减少,尺寸明显减小,接头强度严重下降。分析了表面生长Al4B2O9晶须对Al_2O_3陶瓷表面润湿性的影响,发现在真空条件下,含有活性元素的Ag Cu Ti钎料能够润湿生长有晶须的陶瓷表面,液态钎料在该表面的润湿为反应润湿,晶须间的毛细作用可以促进液态钎料的铺展。随后,以AgCu Ti为中间层对Al_2O_3(W)进行了真空钎焊,研究了钎焊工艺参数对接头微观结构及机械性能的影响规律。晶须/钎料界面由外层的(Cu,Al)3Ti3O化合物和内层的含Ag、Ti的氧化物、Ti B2和(Cu,Al)3Ti3O纳米颗粒的过渡层组成。随着连接工艺参数的提高,晶须与钎料间反应加剧,最终转变为纳米尺度的化合物颗粒弥散分布在焊缝中。当晶须保留在焊缝中时,接头抗弯强度明显高于未生长晶须的Al_2O_3陶瓷接头。820℃/10min条件下所得接头抗弯强度达313MPa,断口中可明显观察到晶须的拔离和折断现象。Al_2O_3陶瓷表面生长晶须不仅可以提高接头强度,同时还能降低连接温度需求。此外,基于对接头微观结构的观察,分析了接头界面组织的演化机制。采用Ag Cu Ti钎料真空钎焊了Al_2O_3(W)和Ni Al(W),对比分析了钎焊工艺参数对所得接头微观组织及机械性能的影响规律。结果表明,Ni Al合金表面生长晶须后避免了金属基体对液态钎料中活性元素的大量消耗,且晶须保留在焊缝中提高了接头强度。820℃/10min所得接头抗剪强度最大(63MPa)。为避免钎料与晶须间发生剧烈反应,探索了以AgCu钎料对Al_2O_3(W)和Ni Al(W)进行空气钎焊。结果表明,基体表面所生长晶须在大气条件下与共晶液相中的Cu O发生化学反应,随着钎料中Cu含量的降低,晶须的反应程度减弱,接头抗剪强度相应提高。
[Abstract]:Al_2O_3 ceramics with high strength, high temperature resistance, good insulation and other excellent properties, is widely used in vacuum devices. However, with the gradual increase of product performance, the local high temperature under extreme conditions in vacuum devices and Al_2O_3 ceramic connection of stainless steel can not meet the use requirements, seriously affect the reliability of the product, if the use of lightweight and high strength Ni resistant Al alloy to replace the stainless steel at high temperature can improve the performance of product. The conventional ceramic / metal brazing joint has high temperature, residual stress, so this paper proposes the whisker growth on the surface of epitaxial Al_2O_3 ceramics and Ni Al alloy, the growth is directly connected to obtain Al_2O_3 ceramic joint has good high-temperature performance by whiskers and on the surface of Al_2O_3 ceramic whiskers by brazing method (Al_2O_3 (W)) and its growth on the surface of Ni whisker Al alloy (Ni A L (W)) are connected to form a composite weld zone through the regulation of matrix whisker surface reaction, thereby strengthening effect on the brazed joint. In B_2O_3, H3BO3 and B_2O_3+ additives as raw materials in the growth of Al_2O_3 whisker growth on the surface of ceramic and Ni alloy Al, characterized the whisker morphology with SEM, studied the influence of raw materials the composition and morphology of whisker growth process, and the use of XRD and TEM whiskers analyzed the composition, structure and properties of crystal growth, discusses the whisker growth mechanism. The results show that using B_2O_3 as the raw material can be evenly distributed in 950 DEG /4h process, crystal whisker degree good, high growth temperature or holding time is too long to maintain the good form of one-dimensional whiskers; using H3BO3 as raw material obtained by the whisker morphology similar to B_2O_3 as raw material; adding Na Cl as a growth promoter, the whisker root defects, and coarse. The growth direction and angle of the ceramic surface is smaller; add K2SO4 as a growth promoter, it can only obtain crystal whisker of relatively good 1100 degrees in the /2h process, but the growth direction and angle of the ceramic surface is smaller; add Mn O2 as a growth promoter when the relatively small size of.950 whiskers by C whisker as orthorhombic Al4B2O9 phase, whisker 1050 degrees above the orthogonal structure of Al18B4O33 phase, whiskers on the surface of the ceramics for epitaxial growth of Al_2O_3 (101 - 0) crystal plane and Al4B2O9 (220) crystal lattice mismatch between only 0.03%, S-L-S self catalytic mechanism with whisker growth process. The results of Al_2O_3 ceramic surface based on whisker growth. Using B_2O_3 as raw material was grown on the surface of Ni alloy Al borate whiskers. At 950 DEG /4h under the condition of the smooth surface, uniform distribution of Al4B2O9 whisker, 1050 DEG C under the condition of /4h except Al4B2O9 also found Ni3 (BO3) and 2, YISHION Ni as the matrix of Ni3 (BO3) crystal structure and growth characteristics of 2 whiskers are analyzed in detail. The surface was directly connected to the whisker growth of Al_2O_3 ceramics, on the middle layer component and connected with the influence of process parameters on the morphology and structure obtained joint high strength, analyzes the mechanism of joint connection. YISHION B_2O_3 the middle layer in the lower income process parameters in the joint whisker size is small, with the residues of B_2O_3. With increasing the brazing temperature or holding time, can through the weld growth of ceramic whisker to achieve a direct connection increases, the joint strength increased, /4h 1100 degrees under the conditions of the joint of high temperature of 800 DEG C the highest flexural strength (27MPa) the fracture occurred in the whisker, internal connection or a longer period of time. The high temperature insulation joint is not conducive to the growth of aluminum borate or retained by one-dimensional form. When adding K2SO4 or Mn O2 in B_2O_3, The joint MICROTEK to drastically reduce the number and size was significantly decreased, the joint strength decline. Analysis of the impact of growth on the surface of Al4B2O9 whisker on the wetting of the surface of Al_2O_3 ceramic, found under vacuum, containing active element Ag Cu Ti solder can wet the growth surface of ceramic whiskers, wetting the surface of the liquid for reactive wetting, capillary action between whisker can promote the spreading of liquid solder. Then, using AgCu Ti as the middle layer of Al_2O_3 (W) by vacuum brazing, soldering on the influences of process parameters on the microstructure and mechanical properties of joints. The whisker / solder interface by the outer layer (Cu, Al) Ag the 3Ti3O compound and the inner layer, the oxide of Ti, Ti and B2 (Cu, Al) 3Ti3O transition layer of nano particles. With the connection parameters increased, the reaction between the whisker and the solder intensified, eventually into the nano scale Compound particles dispersed in the weld. When the whiskers retained in the weld, the bending strength of the joint was significantly higher than that of joint income did not grow whisker of Al_2O_3 ceramic joint.820 degree under the condition of /10min flexural strength is 313MPa, observed that the whiskers off and break the surface of.Al_2O_3 ceramic whisker growth phenomenon can not only improve the joint strength at the same time can reduce the fracture, connect the temperature requirements. In addition, the observation on the joint microstructure based on the analysis of the evolution mechanism of the interface. Using Ag Cu Ti vacuum brazing of Al_2O_3 (W) and Ni Al (W), comparative analysis of the influence of brazing parameters on the microstructure and mechanical properties Ni. The results showed that the surface of Al alloy whiskers can avoid the large consumption of metal matrix on the liquid filler active elements, and retained in the weld whisker improves the joint strength of.820 C /10min the maximum shear strength (63MPa). In order to avoid severe reaction between solder and whisker, was investigated using AgCu solder on Al_2O_3 (W) and Ni Al (W) air brazing. The results showed that the growth of whiskers and substrate surface eutectic liquid phase under atmospheric conditions Cu O chemical with the reaction, reduce the content of Cu in the solder, reaction degree of whiskers decreased, a corresponding increase in shear strength.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG454

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