Beam deflection effects on the microstructure and defect creation on electron beam welding of molybdenum to Kovar

Beam deflection effects on the microstructure and defect creation on electron beam welding of molybdenum to Kovar

[Display omitted] During welding without beam deflection, the weld zone primarily consists of columnar crystals. A reaction layer is detected along the fusion line on the molybdenum side, which is the weak zone of the joint. A ductility dip crack is observed in the heat affected zone on the molybden...

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Bibliographic Details
Published in:Journal of materials processing technology Vol. 267; pp. 280 - 288
Main Authors: Chen, Guoqing, Yin, Qianxing, Guo, Chenghe, Zhang, Binggang, Feng, Jicai
Format: Journal Article
Language:English
Published: Amsterdam Elsevier B.V 01-05-2019
Elsevier BV
Subjects:
Base metal
Beam deflection
Deflection
Economic impact
Electron beam welding
Fracture mechanics
Heat affected zone
Intergranular fracture
Kovar
Kovar (trademark)
Mechanical properties
Microhardness
Microstructure
Molybdenum
Morphology
Tensile strength
Welded joints
Mechanical properties
Electron beam welding
Microstructure
Molybdenum
Kovar
Beam deflection
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Summary:[Display omitted] During welding without beam deflection, the weld zone primarily consists of columnar crystals. A reaction layer is detected along the fusion line on the molybdenum side, which is the weak zone of the joint. A ductility dip crack is observed in the heat affected zone on the molybdenum side. The microhardness of the weld zone is higher than that of the base metal. The tensile strength of the joint is only 190 MPa. The joint fracture along the fusion line on the molybdenum side exhibit an intergranular and cleavage fracture mode. During welding with a 0.6 mm beam deflection to Kovar, the weld zone exhibits equiaxed crystals. The morphology of the reaction layer on the molybdenum side changes compared with that without beam deflection. No cracks are observed in the heat affected zone on the molybdenum side. The tensile strength of the joint increases resulting from the beam deflection to Kovar, which exceeds 260 MPa when the beam deflection is 0.6 mm. The strengthening mechanism of electron beam welded joints under a condition of beam deflection is proposed.
ISSN:0924-0136
1873-4774
DOI:10.1016/j.jmatprotec.2018.12.017