【作者】 王宇欣；

【导师】 冯吉才；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 置氢钛合金,即通过热氢处理技术来改变钛合金的相组成和微观结构,得到的热塑性、热加工性及扩散性均有所改善的钛合金,这是材料科学领域新兴的一个热门方向。目前,国内外的研究主要集中在置氢钛合金热塑性、热加工性以及残钛处理等方面,而对其连接方面的研究很少。C/SiC复合材料具有优异的耐高温、耐磨及抗氧化的特性。因此,实现两种新材料有效连接,既可以应用于先进火箭推力室,又能为置氢钛合金与异种材料的连接提供了技术参考。本文采用AgCu箔与Ni箔实现置氢TC4钛合金与C/SiC复合材料的钎焊连接,研究钎焊工艺参数对接头微观组织的影响规律；揭示界面产物形成的热力学因素及机理；分析连接工艺参数对接头力学性能影响规律,解明接头的断裂行为机制,优化连接工艺。采用AgCu箔连接时,典型的界面结构为：置氢TC4钛合金／针状韦德曼组织/[Ti(s.s)+Ti2Cu]过共析组织／(Ti2Cu+TiCu+Ti3Cu4)扩散带/Ag(s.s)+Cu(s.s)/TiCu+ Ti5Si3Cx/TiC/C/SiC复合材料。当T=840℃/t=10min时,接头抗剪强度达到最高值97MPa。随着钎焊规范的提高,接头的抗剪强度均先增大后减小,TiC反应层为断裂路径的关键。采用纯Ni箔钎焊时,典型的界面结构为：置氢TC4钛合金／过共析组织[Ti2Ni+Ti(s.s)]/Ti2Ni+少量过共晶组织[Ti2Ni+Ti(s.s)]/TiC/C/SiC复合材料。钎焊规范提高,接头界面产物没有明显的变化。钎缝中部Ti2Ni层中原本断续分布的灰黑色块状的Ti(s.s)逐渐长大；钛合金侧Ti2Ni+Ti(s.s)过共析组织厚度不断增大,α-Ti的生长更为粗大。当T=1070℃/t=15min时,接头的抗剪强度最高,达到110MPa。氢改善钛合金钎焊连接性的主要表现在：氢通过降低α→β转变温度、改变钛合金微观组织和增加位错密度,提高了钛合金的超塑性流变能力,与钎料箔达到良好的接触；氢的分解活化钛合金待焊表面,使钎料和待焊母材较快达到原子间接触；氢引起的弱键效应可降低原子结合能,增强空位密度及其迁移能力,从而使得元素间互扩散与自扩散能力增强,原子间的扩散与反应更充分。本文还采用综合热分析研究了置氢TC4钛合金的放氢特性,发现置氢TC4钛合金在600℃-950℃之间脱氢分解,温度为750℃时脱氢反应率达到最大值。并对TiC反应层进行了热力学和动力学分析,通过分析其成长规律,获取了反应层成长动力学参数,得到了反映反应层成长行为的动力学方程。更多还原

【Abstract】 Titanium and hydrogen processing technology (THT) was used to change the alloy phase composition and microstructure in order to improve thermoplastic, thermal processing and diffusion of titanium alloy. THT was a hot new direction in the field of materials science. Present studies are most focused on the thermoplastic, hot workability and the residual of hydrogen titanium alloy, but there were few studies on their connectivity. C/SiC composite had excellent high temperature, wear and antioxidant properties. Therefore, to achieve an effective connection of the two new materials, could both be used in advanced rocket thrust chamber, but also provide a technical reference for connection of the hydrogenation titanium alloys and dissimilar materials. In this paper, AgCu foil and Ni foil were used for solder joint of hydrogen achieved Alloy TC4 and C/SiC composite. The purpose was to study the influence of brazing parameters on microstructure of joints;reveal the thermodynamics of interface product and its formation mechanism; study the influence of connection parameters on mechanical properties of joint; explain the fracture behavior of joints; optimize connection process.AgCu foil connection had a typical interface structure:titanium alloys/needle Veidemann organization/[Ti(s.s)+Ti2Cu] hypereutectoid organization/(Ti2Cu+TiCu+ Ti3Cu4) diffusion zone/Ag(s.s)+Cu(s.s)/Ti2Cu+Ti5Si3Cx/TiC/C/SiC Composite. At 840℃,10min insulation, Joint shear strength up to 97MPa. With the increased brazing temperature or holding time, the shear strength of joints first increased and then decreased, TiC reaction layer is the key to breaking the path.Pure Ni foil soldering, the typical interface structure:hydrogen TC4 titanium alloy/hypereutectic structure [Ti2Ni+Ti(s.s)]/Ti2Ni+a small amount of hypereutectic structure [Ti2Ni+Ti(s.s)]/TiC/C/SiC composites. Improveing brazing Specification, the joint interface product did not change significantly. The original dark gray block of Ti (ss) distribut in the Ti2Ni layer growed up; The thickness of Ti2Ni+Ti(s.s) eutectic on titanium side had been increased, a-Ti growing more coarse. At 1070℃,15min insulation, the joint shear strength is 110MPa and the highest.Hydrogen could improve brazing connectivity of titanium alloy for:Hydrogen could reduce theα→βtransition temperature which can change the alloy microstructure and increase dislocation density, improve the superplastic flow capacity of titanium alloy, achieve a good contact to solder foil. The decomposition of hydrogen activated the surface of the welded titanium, so solder and base materials could be soldered fast to atomic contacts; the addition of hydrogen in titanium. Caused vacancy concentration, increased the host elements Ti and alloying element diffusion and mutual diffusion coefficient, so that the diffusion rate increases and the diffusion distance increases, Diffusion and reaction between atoms became better.The hydrogen TC4 titanium alloy dehydrogenation decomposition between 600℃-950℃. At 750℃, the rate of dehydrogenation reaction rate is maximum. By analyzing the pattern of growth for the TiC reaction layer, this paper obtained growth kinetics parameters, then got the dynamic equations for growth behavior of the reaction layer.更多还原