|
7180 |
|
Tuesday, June 21, 2022, Saal Brüssel 4:00 PM Properties of brazed joints |
|
Influence of the microscopic condition of brazing fillets on the fracture behavior of brazed joints |
|
Julia Bültena* / Dortmund University of Technology, Germany Wolfgang Tillmann / TU Dortmund, Institute of Materials Engineering, Germany Kirsten Bobzin/ RWTH Aachen, Germany Marvin Erck/ RWTH Aachen, Germany Hendrik Heinemann/ RWTH Aachen, Surface Engineering Institute, Germany Julian Hebing/ RWTH Aachen, Surface Engineering Institute, Germany Andre Jöckel/ Fraunhofer Institute for Structural Durability and System Reliability LBF, Germany |
|
Common methods for evaluating the fatigue strength of brazed joints do not take account of the microscopic fillet condition and the damage mechanisms in a brazed seam. However, it has been demonstrated that a macroscopic consideration of the brazing fillet leads to an imprecise prediction of the fatigue strength. The objective of this work is to exemplify that it is necessary to consider the microscopic fillet topography for a realistic prediction of the fatigue strength. Therefore, the damage mechanisms of vacuum brazed peel specimens made of steel 1.4301 and Cu110 brazing alloy were analyzed. Intermittent fatigue tests were carried out, during which the specimens were unclamped after a defined number of cycles and microscopically inspected by computertomography. This test procedure was carried out until failure. The fracture surfaces were examined by scanning electron microscopy and energy dispersive spectroscopy. For all specimens, crack initiation was located in the brazing fillet. The reason was the open-pore void structure in the dendritically solidified filler metal, which represent geometric notches in the brazing fillet that act as the starting point for crack formation. The crack path itself varies, but it is obvious that defects in the brazing filler metal influence the crack growth direction. |