【作者】 郑德双；

【导师】 王娟；

【作者基本信息】 山东大学 ， 材料加工工程， 2013， 硕士

【摘要】 本课题采用Ag-Cu-Ti、 Cu-Mn-Co和镍基钎料(Ni-Cr-P、 Ni-Cr-Si-B),通过真空钎焊技术实现了Mo-Cu合金与Cr18-Ni8不锈钢的钎焊连接,并对钎焊接头的显微组织和性能进行了研究,为Mo-Cu/Cr18-Ni8复合构件的焊接制备提供了试验基础和理论依据,对于扩大Mo-Cu合金的工程应用具有重要的应用价值和理论意义。试验采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、显微硬度计和微控万能电子试验机对Mo-Cu/Cr18-Ni8钎焊接头的显微组织、元素扩散分布、显微硬度、剪切强度和断裂特征进行了研究。实验结果表明,Ag-Cu-Ti、 Cu-Mn-Co和镍基钎料均能实现Mo-Cu合金和Cr18-Ni8不锈钢的真空钎焊链接,钎料与母材润湿良好,界面结合致密,钎焊接头性能优异,无裂纹、显微空洞、未钎合等缺陷。Ag-Cu-Ti钎料钎缝主要由Cr18-Ni8不锈钢一侧的Ag-Cu共晶组织和Mo-Cu合金一侧的富铜固溶体组成,钎缝的显微硬度低于两侧母材；钎焊接头的剪切强度为75MPa,剪切裂纹起源于Cr18-Ni8不锈钢一侧的连接界面处,并向钎缝共晶组织中扩展,剪切断口呈现剪切塑性断裂特征。Cu-Mn-Co钎料钎缝组织为单相Cu-Mn固溶体组织,显微硬度低于两侧母材；接头的剪切强度为192MPa,剪切断口呈现以塑性断裂为主,塑性断裂和脆性断裂相结合的断裂特征；剪切断裂发生于钎缝的铜固溶体基体中,形成塑性断裂断口,Cr18-Ni8不锈钢一侧则形成了河流状的脆性断裂断口。Ni-Cr-P钎料钎焊接头显微组织主要由Ni-Cr-P固溶体基体组织、钎缝中心的Ni-P共晶组织、钎缝两侧的Ni-Cr(Fe、 Mo)固溶体和Ni5P2、 Cr3P等析出相组成；钎缝的显微硬度高于两侧母材的显微硬度,在Ni-P共晶组织处出现最高值(560Hv);钎焊接头剪切强度为155MPa,剪切断口呈现穿晶断裂和撕裂韧窝断裂相混合的断裂特征,具有一定的塑性；断裂首先发生于Mo-Cu合金一侧连接界面处的穿晶区,剪切裂纹向钎缝中扩展,形成剪切韧窝断裂的断口。Ni-Cr-Si-B钎料接头钎缝组织为y-Ni(Cu、 Fe)固溶体、Ni3S、 y-Ni固溶体和Ni3B共晶,非晶态钎料钎焊接头钎缝中间的共晶组织消失,形成单相γ-Ni固溶体组织；钎缝的显微硬度高于两侧母材,在共晶组织处出现最高值；钎焊温度为1040℃时,钎焊接头的剪切强度可达207MPa,剪切断裂起源于Mo-Cu合金一侧的连接界面处,剪切断口呈现撕裂断裂、解理断裂和穿晶断裂相混合的断裂特征；钎焊温度为1120℃,钎焊接头的剪切强度高达343MPa,剪切断口表现为明显的脆性断裂特征,剪切断裂开始于钎缝基体固溶体,并在钎缝中扩展,形成微解理台阶的脆性断口。更多还原

【Abstract】 In this work, the vacuum brazing of Mo-Cu alloy and Crl8-Ni8stainless steel was carried out with Ag-Cu-Ti, Cu-Mn-Co and Ni-based filler metal(Ni-Cr-P, Ni-Cr-Si-B) and the microstructure and properties of Mo-Cu/Cr18-Ni8brazed joint was analyzed. The study would provied theory and experiment basis, as well as has great application value and theoretical significance for the engineering application of Mo-Cu alloy and Crl8-Ni8stainless steel.The microstructure, diffusion and distribution of element, microhardness, shear strength and fracture characteristics were tested by means of optical microscope(OM), scanning electron microscope(SEM), energy dispersive system(EDS), microhardness tester and microcomputer control electron universal testing machines.The results showed that Ag-Cu-Ti, Cu-Mn-Co and Ni-based filler metal(Ni-Cr-P, Ni-Cr-Si-B) had a good wetting with Mo-Cu alloy and Cr18-Ni8stainless steel and the vacuum brazed joint has no crack or micro-hole with good metallurgical bonded interface.The Ag-Cu-Ti filler metal brazed seam was mainly comprised of eutectic and Cu-rich phase and the microhardness of brazed joint was lower than that of Mo-Cu alloy and Cr18-Ni8stainless steel. The shearing strength of Mo-Cu/Cr18-Ni8joint was about75MPa and the shear fracture exhibited plastic feature with shear dimple. The flake crack initiated in the interface between braze seam and Cr18-Ni8stainless steel and propagated along the interface and even eutectic.The Cu-Mn-Co filler metal brazed seam was mainly composed of single Cu-Mn solid solution phase with good plasticity and the microhardness of brazed joint was lower than that of based metal. The shearing strength was192MPa and shear fracture exhibited mixed ductile-brittle fracture feature. The fracture originated from the brazing seam forming plastic fracture and crack propagated to the Cr18-Ni8 stainless steel shaping river pattern brittle fracture.The Ni-Cr-P filler metal brazed seam was mainly consist of Ni-Cr-P solid solution, Ni-P eutectic, Ni-Cr(Fe, Mo) solid solution, N15P2and Cr3P precipitated phase. The microhardness of brazed joint was higher than that of based metal and the Ni-P eutectic was the highest, reached560Hv. The shearing strength was155MPa and shear fracture exhibited mixed ductile-brittle fracture feature with transgranular fracture, ductile dimples and tearing edges. Fracture originated from interface between brazing seam and Mo-Cu alloy and crack propagated to the barzing seam.The Ni-Cr-Si-B filler metal brazed seam was mainly made up of y-Ni(Cu, Fe) solid solution, Ni-B eutectic, while Ni-B eutectic disappeared and formed single y-Ni solid solution phase in amorphous filler metal brazed seam; the microhardness of brazed joint was higher than that of based metal, which the Ni-B eutectic was the highest. When the brazing temperature was1040℃, the shearing strength was207MPa and shear fracture showed mixed tear fracture, cleavage fracture and transgranular fracture, which the fracture originated from interface beside Mo-Cu alloy. When the brazing temperature was1120℃, the shearing strength reached343MPa and shear fracture showed obvious brittle fracture. The fracture located at y-Ni(Cu, Fe) solid solution in center of brazed seam formed brittle fracture with micro-cleavage step.更多还原