【作者】 谭佳梅；

【导师】 周上祺；

【作者基本信息】 重庆大学 ， 材料学， 2007， 硕士

【摘要】 在国际热核聚变反应堆中,需要用Be与Cu合金复合结构作为面向等离子体材料,在工程上主要采用扩散连接方法或者钎焊来实现Be与Cu合金的良好连接。本文选择热等静压扩散连接工艺对Be与Cu合金进行连接。采用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)等分析手段研究连接接头界面组织结构和剪切断口断裂机制和物相组成。通过量子化学软件Material stuidio软件中的Castep模块计算可能生成的金属间化合物的生成自由能,结合“通量-能量原则”研究接头界面反应层的形成;对金属间化合物的原子轨道集居数和键重叠集居数进行分析。采用Castep计算在空位机制下Be、Cu、α-Ti和β-Ti的空位形成能和扩散迁移能,对Be、Cu、α-Ti和β-Ti与单空位结构的原子轨道集居数进行了分析。在850℃时采用Ti作为中间层连接Be与Cu合金,得到的接头连接界面形成了TiBe2、α-Ti固溶体(其中有一定量的析出相Ti2Cu)、Ti2Cu、Ti3Cu4、Ti2Cu3和TiCu4连续过渡的层状结构。接头剪切强度较低,剪切断口为解理-沿晶混合断裂,断口X射线衍射分析表明断裂发生在金属间化合物Ti2Cu和Ti3Cu4相的交界处。采用AlSiMg、Al、Ti箔层作为中间层,并在Be端镀Al、CuCrZr端镀Ti后在555℃时热等静压扩散连接Be/CuCrZr,接头界面结合致密,生成的金属间化合物为Ti3Cu4相。接头剪切强度较低,其断口断裂方式主要为解理-韧窝断裂。在620℃时,CuCrZr端镀Cu层后扩散连接的Be/CuCrZr接头,在靠近Be端生成了Be2Cu相,在Cu端生成了Cu+BeCu相。Cu镀层与原始Cu合金界面明显,样品剪切强度低,为准解理断裂,断裂发生在Cu镀层与基体的分界处。在580℃时,直接连接的Be/CuCrZr接头界面扩散层由Be端的Be2Cu相和CuCrZr端的Cu+BeCu相组成,样品剪切强度较高,断裂方式为韧窝-沿晶混合断裂。断裂发生在Be2Cu与BeCu相的界面处。而在Be端镀5μmTi、CuCrZr端镀不同厚度Cu后连接的Be/CuCrZr样品,Ti在Cu中的扩散距离大于在Be中的扩散距离,发生了不对称扩散。扩散层内有Ti3Cu4和TiCu4等金属间化合物生成。断裂方式均为准解理断裂。采用10μmCu和50μmCu的样品,Be、Ti扩散不充分,接头于Be、Ti界面处断裂,结合强度也较低。而Cu镀层为30μm的样品,接头于扩散层内的α-Ti与Ti3Cu4的界面处断裂,接头结合强度高。计算了接头中金属间化合物的生成自由能,并分析了接头中界面反应层的形成机理。由此得出的结论与能谱和XRD物相分析得出的结果相吻合。计算了金属间化合物的原子轨道集居数和键重叠集居数,讨论了金属间化合物的结合状态。计算了Be、Cu、α-Ti和β-Ti互扩散的扩散迁移能,很好地说明了Ti发生不对称扩散的原因。更多还原

【Abstract】 Be/Cu-alloy compound structure is used as plasma facing material for the International thermonuclear Experimental Reactor (ITER).Bonding of Be to Cu-alloy was completed by diffusion bonding or brazing. Hot Isostatic pressing (HIP) diffusion bonding of Be to Cu-alloy was carried out in this paper. Scanning Electron Microscope (SEM), Energy Dispersive Spectrum (EDS), X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectrumscopy (XPS) analysis were employed to investigate the interface structure of joint, fracture mechanism and phases of shear fracture surface were also studied. The formational free energy of the possible intermetallic compounds was calculated by Castep module of Material Studio, according to“flux-energy principal”to confirm the formation of interface reaction. The atomic population and overlap population of intermetallic compounds were analyzed. The formational energy of vacancy and diffusion migratory energy of Be, Cu,α-Ti andβ-Ti were calculated by Castep, the atomic population of simple-vacancy to Be, Cu,α-Ti,β-Ti were analyzed. Be to Cu-alloy were Bonded used Ti as interlayer under bonding temperature 850℃. It was found that TiBe2、α-Ti(there was some Ti2Cu phase segrated)、Ti2Cu、Ti3Cu4、Ti2Cu3 and TiCu4 layered structure were formed on the joint interface. The shear strength of joints were lower. The fracture was cleavage-intergranular crack. The XRD analysis showed that the joints ruptured around the interface between Ti2Cu layer and Ti3Cu4 layer.Physical Vapor Deposite (PVD) Al on Be, Ti on CuCrZr, after this, used AlSiMg、Al and Ti foil as interlayers, Bonding Be to CuCrZr were tested under bonding temperature 555℃.The interface of the interface combined compactly, the intermetallic compounds Ti3Cu4 was formed in the interface between Ti and Cu. The shear strength of the joint was lower; the fracture was chiefly cleavage-dimple crack.After PVDing Cu on CuCrZr, Bond Be to CuCrZr under 580℃.Be2Cu phase on the Be side and Cu+BeCu phase on the CuCrZr side were observered. The interface between copperizing layer and original CuCrZr matrix were obvious. The shear strength was lower, quasi-cleavage crack occurred and ruptured around the interface between the copper layer and CuCrZr matrix.The interface layer of joint which gained by bonding Be to CuCrZr by direct HIP diffusion bonding under 580℃consisted of Be2Cu phase on the Be side and Cu+BeCu phase on the CuCrZr side. The joint strength was well , fracture occurred dimple-intergranular crack and ruptured around the interface between Be2Cu and BeCu phase. In contrast, the joints bonded Be(PVD 5μm Ti on it) and CuCrZr( PVD Cu with different thickness on it),Ti tended to diffuse in Cu rather than in Be, and unsymmetrical diffusion occurred. There were Ti3Cu4 and TiCu4 intermetallic compounds formed on the interface. All of fractures were quasi-cleavage crack.The diffusion between Be and Ti was incomplete for the joints which the thickness of Cu was respectively 10μm and 50μm, and fracture occurred around the interface between Be and Ti,the joints’strength were lower. However ,for the sample which the thickness of copperizing layer was 30μm, the joint ruptured around the interface betweenα-Ti and Ti3Cu4,and the shear strength was upper.The formational free energy of the possible intermetallic compounds was calculated by Castep module. According to the result, the formational mechanism of interface phase on the joints was studied. The atomic population and overlap population of intermetallic compounds were calculated, and the combined states of the intermetallic compounds were discussed. The diffusion migratory energies when Be ,Cu,α-Ti andβ-Ti diffuse in each other were calculated, from the result, it would be explained why that unsymmetrical diffusion occurred for Ti in Be and Cu.更多还原