Wetting, structure and properties of Al/Al2O3 interfaces
Natalia Sobczak Instytut Odlewnictwa, Zakład Fizykochemii Metali i Stopów, ul. Zakopiańska 73, 30-418 Kraków
Annals 3 No. 7, 2003 pages 301-312
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abstract The paper discusses the literature data and results of own research on wettability in the Al/Al2O3 system. The wettability tests were curried out by the sessile drop method using different testing procedures (CH - contact heating of Al and substrate samples up to the test temperature, CP - capillary purification technique which allows the separate heating of the samples while a drop is produced by squeezing a metal through capillary directly at the test temperature) and heating procedure (fast and slow heating) before wettability test. In order to examine the mechanical properties of Al/Al2O3 joints the improved procedure of push-off shear test was applied on solidified sessile drop samples. The results demonstrate that among different phenomena, affecting physico-chemical interaction and resulting wetting and bonding properties in Al/Al2O3 system, the presence of oxide film on Al drop is the most important factor at T < 1173 K, while at T > 1173 K the dissolution of the substrate in molten Al becomes a leading one. For CH technique and the same contact time, increasing temperature results in improvement of both wetting and shear strength, while at T < 1173 K the contact time is responsible for mechanical properties of Al/Al2O3 interfaces. The removal of oxide film from Al drop in CP technique effectively improves low temperature wetting, resulting in high shear strength, comparable to the samples produced by CH at high temperature. Thermo-cycling improves mechanical properties of Al/Al2O3 couples produced at T < 1173 K, but for those obtained at T >1173 K the shear strength of thermo-cycled samples decreases with increasing temperature of wettability test. Key words: wettability, interfaces, composites, Al/Al2O3