Oxidation Behavior of Ag-Cu-Tio Brazing Alloys

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J. Korean Ceram. Soc. > Volume 35(1); 1998 > Article

Journal of the Korean Ceramic Society 1998;35(1): 55.

Ag-Cu-Ti 브레이징 합금의 산화거동

우지호, 이동복, 장희석, 박상환¹

성균관대학교 금속재료공학부
¹한국과학기술연구원 복합기능세라믹스센터

Oxidation Behavior of Ag-Cu-Tio Brazing Alloys

ABSTRACT

The oxidation behavior of Ag-36.8a%Cu-7.4at%Ti alloy brazed on Si3N4 substrate was investigated at 400, 500 and 600$^{circ}C$ in air. Under this experimental condition Si3N4 and Ag were not oxidized whereas Cu and Ti among the brazing alloy components were oxidizied obeying the parabolic oxidation rate law. The activation energy of oxidation was found to be 80kj/ mol which was smaller than that of pure Cu owing to the presence of oxygen active element of Ti. The outer oxide scale formed from the initial oxidation state was always composed of Cu oxides which were known to be growing by the outward diffusion of Cu ions. As the oxidation progressed the concentration gradient occurred due to the continuous consumption of Cu as Cu oxides and consequently build-up of an Ag-enriched layer below the Cu oxides resulted in the formation of multiple oxide scales composed of Cu oxide (CuO) /Ag-enriched layer/Cu oxide (Cu2O) /Ag-enriched layer. Also the inward diffusing of oxygen through Cu oxide and Ag-enriched layers led to the formation of internal oxides of TiO2

Key words: Oxidation, Brazing alloy, Ag, Cu, Ti