Wettability Of Silicon Carbide And Silica By Molten Aluminum Alloys And Their Interfacial Microstructures

Great interests have been attracted to the SiC-reinforced aluminum matrix composites due to their plenty of advantages in use. Thus, in the fabrication of the SiCp/Al composites, wettability of SiC by liquid Al is highly important. However, it has been already reported that the wettability of this Al/SiC system is poor at low temperatures. With the increasing of temperature the wettability is gradually improved,but a brittle Al4C3 phase will be formed at the interface. This will do great harm to the property of the composites.In order to enhance the wettability of the Al/SiC system and control the formation of Al4C3, addition of alloy-elements has been widely used. In this paper we investigated the wetting behavior of Al/SiC system after add chemical elements such as Cu, Ti, Mg, Si into pure aluminum using a modified sessile drop method. We also choose two typical aluminum alloy 2014 Al alloy and Al-12Si-3Cu alloy to study their wetting behavior on the polycrystalline SiC subtrates because their great use in business industry. And this can also apply to the modle of double-elements addition to the Al/SiC system. Pre-oxidation of SiC is a common method in the fabrication of the SiCp/Al composites and it is believed to improve the dispersion of SiC in the liquid aluminum. But very few people test its wettability use wetting test methods. Silica film will be formed after pre-oxidize the SiC. The wettability of the Al alloy of slica will also influnce their wetting behavior on the pre-oxidized SiC substrats. Thus,we also study the wettability of aluminum alloy/SiO2 system.The major conclusions attached in present study are as follows:1. The comparison of our modified sessile drop method and traditional sessile drop method has been pointed out in our work. The pre-contact and pre-reaction between the metal and substrate in the traditional sessile drop method can be avoided using the modified one. We can obtained more accurate statistics of contact angles and work of adhesion. Also, we have more choices to made to get wetting test for different kinds of metal/ceramic system.2. As to the Al/SiC system, the addition of Cu plays no significant role in improving the wettability and even deteriorates that. While addition of Ti remarkably promotes the wetatability, which is attributed to the adsorption of Ti at the solid/liquid interface and the formation of TiCx. The Mg element can promote the wettability only when the concentration is relatively high. The wettability of the Al-12Si-3Cu/SiC system improves with the increasing of temperature,attributing to the existence of Si. The wettability of 2014 Al alloy on the SiC substrate is not that good which can be attributed to the low content of Cu, Mg elements ect.3. The Cu elements have no significant effect on the wettability of Al/SiO2 system and Al/SiCox system. And the addition of Si can not improve the wettability of the two system and even detetiorates that. The final contact angles increase with the increasing of the concentration of Si. Meanwhile the interface reaction is inhibited. The wettability of the Al-Mg/SiCox system is worse than that of the Al-Mg/SiC, attributing to that the pre-oxidation of SiC substrate aggravates the oxidation of the liquid Al alloys drop. Owing to the great affinty between Mg and SiO2, the Mg element can promstied the wettability of Al alloys on the pre-oxidated SiC. The wettabilty of the Al-12Si-3Cu/SiO2 and the Al-12Si-3Cu/SiCox system is bad. And the wettability of 2014 Al alloy on the SiO2 substrate is worse than that on SiC and SiCox.