Deformation Mechanism of Filler Metal at Brazed Joint Mechanical Properties of Brazed joint (2) by Ken Sasabe and Isao Okane The deformation mechanism of filler metal at brazed joint was discussed in terms of the dislocation theory. The deformation of filler metal at joint depends on the pile-up process of dislocations against joint interface, because the joint interface is very strong as an obstacle. The deformation of filler metal at the joint is devided characteristically into the five

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... from the low stress up to a high stress: (A) Many dislocations piled-up rapidly against joint interfaces. The stress-strain curve is parabolic, and the work hardening ratio is very high. (B) Plastic flow is restricted by the piled-up groupes of dislocations. The stress-strain curve is straight. (C) Filler metal flows plastically. The stress-strain curve is parabolic. At the transition stress (B) to (C), the stress-strain curve shows an apparent yield point. (D) When the stress becomes higher than the yield stress of the base metal, the work hardening ratio becomes smaller than before. (E) Cracks initiate and propagate until failure of the joint occures.