【作者】 李辉；

【导师】 周上祺；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2010， 博士

【摘要】 铍属稀有金属,因其具有密度低,比强度和比热容高以及导热性好等优点,被广泛运用于核能、航空和航天工业。铍的缺点是延展性差,脆性大,从而给铍构件的设计和制造带来不少困难。另外,铍的化学活性高,在高温下极易氧化,它与许多金属能生成脆性的金属间化合物,影响构件的性能和使用寿命,因而研究铍/不锈钢热静压扩散连接工艺、成分、组织、结构和性能的关系,具有重要的理论意义和实用价值。本项目通过对Be/HR-1、Be/Cu/HR-1、Be/Al/HR-1和Be/Ag-Cu/HR-1不锈钢热静压后成分、组织、结构和性能的研究,得出了以下结果:①Be/HR-1不锈钢热静压时,铍、铁两元素只能生成固溶度很小的有限固溶体,故扩散形式主要为沿晶界扩散,生成的脆性金属间化合物主要分布在晶界上。②Be/Cu/HR-1不锈钢热静压时,因铜在铍中的固溶度较大,在铁中的固溶度小。故铍铜之间的扩散既有沿晶界扩散,也有晶内扩散;铜在不锈钢中的扩散主要为沿晶界扩散。因此,铍/铜/HR-1不锈钢热静压时,出现了明显的铜往两侧不对称扩散现象。③Be/Al/HR-1不锈钢热静压时,铝在铁中固溶度约为20%(原子百分数,下同),而与铍基本上不互溶,两者形成共晶。因此,铝在铁中的扩散既有沿晶界扩散,也有晶内扩散,而在铍中的扩散主要为沿晶界扩散。④Be/Ag-Cu/HR-1不锈钢热静压时,因铜在铍中的固溶度较大,银在铍中的固溶度小,铜往铍中扩散容易进行,导致银铜合金中的银铜分离,也导致中间层往两侧的不对称扩散现象发生。⑤Be/HR-1和Be/中间层/HR-1不锈钢热静压后得到的都是层状组织,层状组织的层面近似垂直于外力方向,层与层之间近似平行。⑥Be/HR-1不锈钢热静压时,除基材物相α-Be和γ-相之外,还生成铍铁、铍镍、铍铬等金属间化合物;Be/中间层/HR-1不锈钢热静压时,除两基材元素间形成金属间化合物外,中间层的合金元素也将与基材的元素形成金属间化合物。生成的金属间化合物主要沿晶分布。⑦Be/HR-1和Be/中间层/HR-1不锈钢热静压试样的失效断口均为脆性断口。⑧试验连接试样的抗拉强度从大到小的排列顺序为:Be/Ag-Cu/HR-1,Be/Cu/HR-1和Be/HR-1不锈钢。⑨选用的中间层材料元素应尽可能与基材的元素互相固溶或生成混合物,尽量避免产生脆性的金属间化合物。⑩压力的作用,不仅仅是使连接界面的接触面积逐渐扩大,它还将使试样产生动态形变再结晶和扩散性蠕变,也能影响扩散焊区的扩散速度和晶粒大小。单轴向压力作用下,基材或扩散焊区出现织构。⑾用计算机模拟的热静压试样的成分分布与实验值比较吻合,计算机是优化热静压工艺的重要手段。更多还原

【Abstract】 Metal beryllium is the rare metals, and is widely applied to industry of nuclear, aviation and spaceflight due to the characteristic of low density, high strength ratio, high specific heat and excellent property of heat. But beryllium’s high brittleness and low ductibility make its component design and producing much difficulty. Furthermore, beryllium is an active element ,which is prone to form brittle inter-metals, which influence the component’s use and life. So researching the diffusion bonding in the hot pressing between Be and HR-1 stainless steel plays an important role in theory and practice, especially studing the relationship among diffusion bonding technique, components, structure and performances.The components, structures and performances of diffusion bondings in the hot pressing of Be/HR-1 stainless steel, Be/Cu/HR-1 stainless steel, Be/Al/HR-1 stainless steel and Be/Ag-Cu/HR-1 stainless steel have been studied in this item, the conclusions are as follows:①D uring the process of hot pressing of Be/HR-1 stainless steel, Fe and Be form incomplete solid solution with very little solubility limit. Therefore the dominating way is diffusing along the grain boundaries, and brittle inter-metallic compounds form mainlyon the grain boundaries.②D uring the process of hot pressing of Be/Cu/HR-1 stainless steel, the solubility limit of Cu in Be is larger than in Fe. Therefore Cu diffuses into the Be not only along the grain boundaries but also through the grains, while diffuses along the grain boundaries largely in the stainless steel, which is why there is an obvious asymmetry diffusion of Cu into Be and stainless during the hot processing.③T he solubility limit of Al in iron is about 20%(atom%)at room temperature , whereas it does not dissolve in Be and they form eutectic. So during the process of hot pressing of Be/Al/HR-1stainless steel, Al diffuses into the iron not only along the grain boundaries, but also throughout the grains, which diffuses mainly along the grain boundaries in the Be.④D uring the process of hot pressing of Be/Ag-Au/HR-1 stainless steel,the solid solubility limit of Cu in Be is larger than that of Ag in Be, so it is easier for Cu to diffuse into Be, which leads to separation of Ag and Cu in Ag-Cu alloys and asymmetry diffusion of intermediate layer into the two sides. ⑤A fter hot pressing, there are lamellar structures in Be/HR-1 stainless steels and Be/interlayer/HR-1 stainless steels, and the lamellar layers are almost perpendicular to the outside forces direction, with the layers almost paralleling to each other.⑥During the process of hot pressing of Be/HR-1 stainless steel, Be-Fe, Be-Ni, Be-Cr and so on inter-metallic compounds are formed, while during the process of hot pressing of Be/interlayer /HR-1 stainless steel, elements of interlayer and matrix as well as between two matrix materials form inter-metallic compounds. Inter-metallic compounds form mainly on the grain boundaries.⑦Fractures of Be/HR-1 stainless steels and Be/interlayer /HR-1 stainless steels both are brittle.⑧T ensile strength of Be/Ag-Cu/HR-1 stainless steel is most among the tested materials, as followed by that of Be/Cu/HR-1 stainless steel and Be/HR-1 stainless steels.⑨Elements of chosen interlayer materials should form solid solution or eutectic with that of matrix materials as possible in order to avoid the formation of brittle inter-metallic compounds.⑩Pressure not only makes the contact areas of connected interface enlarge gradually but also cause dynamic formed re-crystallization and diffusion creep, which affects diffusion ratio of diffusion welding zones and grain size. Matrixes or diffusion welding zones may form texture under pressure of a single axle direction.⑾The simulation of concentration profile of hot pressings specimens can accords with the experimental profile. The computer is an important tool toptimize the hot processing parameters.更多还原