| dc.description.abstract | The purpose of the study is aimed at investigating the difference of growth and decomposition of aluminum oxide film affected by aluminum alloys during adding heat and holding temperature. Experimental specimens are made by “sandwich type”, divided into up-specimen, middle layer and down-specimen. The alloys used in the up-specimen are pure Al (99.999%), commercial pure Al (99.82%), Al-7%Si alloy, Al-13%Si alloy, Al-0.5%Mg alloy, A356.2 alloy, A356.2-high Sr alloy, respectively. Middle layer is oxide films grown on Al surface at high temperature. Down-specimen is pure Al (99.999%). Make up-specimen and down-specimen combine, and place the specimen in heat furnace under argon atmosphere. The heat furnace heats from room temperature to 750℃ and then holds temperature, and then the specimen is holded by change of time (12,15,20 minutes) to compare with growth and decomposition of oxide films affected by alloy components and change of time.
Experimental results prove that growing oxide films naturally at high temperature (610℃) is γ-Al2O3. Because permeated and corroded by Al liquid，aluminum oxide is decomposed and scatters Al substrates. When holding time increases, aluminum oxide is corroded and decomposed more seriously, and finally up-specimen and down-specimen fuse together.
For effects of alloy components: the specimen includes Si element, Si adheres to oxide films(Al2O3) and several Si diffuse into films by Al liquid. The specimen includes Mg element, Mg diffuses into oxide films by Al liquid, combines with and react to films rapidly. The specimen includes Sr, Si, and Mg elements, Sr diffuses into eutectic Si and hinders which Mg diffuses into and combines with oxide films. If Si quantity in the specimen increases, the amounts of Si adhering oxide films increase obviously. Further, the action delays which Al liquid permeates aluminum oxide, and increases corroded and decomposed time of aluminum oxide. Therefore, oxide in the middle layer grows at high holding temperature and thickens. | en_US |