Formation of Interfacial Reaction Layers in Al 2 O 3 /SS 430 Brazed Joints Using Cu-7Al-3.5Zr Alloys

The formation of interfacial reaction layers was investigated in an α-Al₂O₃/430 stainless steel (SS430) joint brazed using a Cu-7Al-3.5Zr active brazing alloy. Brazing was conducted at above its eutectic temperature of 945 °C and below liquidus 1045 °C, where liquid and solid phases of the brazing alloys coexists. At 1000 °C, the liquid phase of the brazing alloy was wet onto the α-Al₂O₃ surface. Zr in the liquid phase reduced α-Al₂O₃ to form a continuous ZrO₂ layer. As the dwell time increased, Zr in the liquid phases near α-Al₂O₃ interface was used up to thicken the reaction layers. The growth kinetics of the layer obeys the parabolic rate law with a rate constant of 9.25 × 10^−6 cm·s^−1/2. It was observed that a number of low yield strength Cu-rich particles were dispersed over the reaction layer, which can release the residual stress of the joint resulting in reduction of crack occurrence.

Abstract licence: CC BY

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