Microstructural considerations of enhanced tensile strength and mechanical constraint in a copper/stainless steel brazed joint

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:796

Article

Li, Y.¹  Parfitt, D.¹  Flewitt, P. E. J.²  Hou, X.³  de Fonseca, J. Quinta⁴  Chen, B.^1,5 

[1] Coventry Univ, Inst Future Transport & Cities, Coventry CV1 5FB, W Midlands, England

[2] Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England

[3] Ctr Excellence Adv Mat, Dongguan 523808, Peoples R China

[4] Univ Manchester, Mat Sci Ctr, Manchester M13 9PL, Lancs, England

[5] Univ Leicester, Sch Engn, Leicester LE1 7RH, Leics, England

关键词: Strengthening mechanism;    Geometrically necessary dislocation;    Plastic flow;    Brazing;    Mechanical constraint;   

DOI  :  10.1016/j.msea.2020.139992

来源: Elsevier

【 摘 要 】

The microscopic and macroscopic material strengthening mechanisms encountered in brazed joints were experimentally investigated and quantified in this work. Microstructural contribution towards the overall strength of a stainless steel brazed joint was evaluated by conducting multi-scale microstructural characterisations. Theoretical evaluation of the collected microstructural data suggests a Cu-Mn solid-solution strengthening enhancement of similar to 200 MPa towards the overall joint strength. The mechanical constraint effect was considered as the macroscopic strengthening mechanism, as revealed by comparing two identical joints but with their interfaces orientated at 90 degrees and 45'with respect to the applied load. Bridgman necking criteria was applied to derive the longitudinal flow stress for the 90 degrees joint configuration. The discrepancy (similar to 330 MPa) between the calculated and experimentally determined strengths can thus be concluded as the contribution of mechanical constraint. In addition, the pile-up of geometrically necessary dislocations (GNDs) was observed at the base-filler metal interface for the 90 degrees joint, but a homogeneous GND distribution was revealed for the 45 degrees one. This observation indicates that GNDs were introduced to accommodate deformation incompatibility imposed by the mechanical constraint. This finding is thus considered as an experimental (microscopic) evidence for strain inhomogeneity due to the presence of mechanical constraint.

【 授权许可】

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