Low-Temperature Interface Reaction Between Titanium and the Eutectic Silver-Copper Brazing Alloy |
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Authors: | J Andrieux O Dezellus F Bosselet J C Viala |
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Affiliation: | (1) Laboratoire des Multimatériaux et Interfaces, LMI, UMR CNRS 5615, Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France |
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Abstract: | Reaction zones formed at 790 °C between solid titanium and liquid Ag-Cu eutectic alloys (pure and Ti-saturated) have been
characterized. When pure Ag-Cu eutectic alloy with 40 at.% Cu is used, the interface reaction layer sequence is: αTi/Ti2Cu/TiCu/Ti3Cu4/TiCu4/L. Because of the fast dissolution rate of Ti in the alloy, the reaction zone remains very thin (3-6 μm) whatever the reaction
time. When the Ag-Cu eutectic alloy is saturated in titanium, dissolution no longer proceeds and a thicker reaction zone with
a more complex layer sequence grows as the reaction time increases. Four elementary chemical interaction processes have been
identified in addition to Ti dissolution in the liquid alloy. These are growth of reaction layers on Ti by solid state diffusion,
nucleation and growth from the liquid of TiCu4, isothermal solidification of silver and, finally, chemical conversion of the Cu-Ti compounds by reaction-diffusion in the
solid state. A mechanism combining these processes is proposed to account for the constitution of Ti/Ag-Cu/Ti joints brazed
at 780-800 °C. |
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Keywords: | chemical potential gradients diffusion paths intermetallics metals ternary system |
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