2009 Volume 50 Issue 1 Pages 192-196
The surface region of the aluminum foams (trade name ALPORAS) was modified through the friction stir processing (FSP) which was performed by using friction phenomena with a high-speed rotating tool. The tool was rotated at speeds ranging from 820 to 2400 rpm, and plunged from the top surface of the aluminum foam, and then traversed at speeds ranging from 50 to 300 mm/min. The surface-modified zone (SMZ) had considerably smoother surface in comparison to the unprocessed zone (UZ). Especially for 1390 rpm and 150 mm/min, the smoothest surface was obtained, which was attributed to the smaller amount of pores in the SMZ. In addition, a very dense layer was formed near the surface of the SMZ through the localized collapse and densification of the cell structure near the surface region, which was attributed to the friction phenomena with the high-speed rotating tool. The mechanical properties of the aluminum foams were significantly improved through the FSP. Especially for 1390 rpm and 150 mm/min, the SMZ exhibited the highest average maximum indentation strength and energy absorption ability, which were equivalent to about 2.2 times the values of the UZ. The tool rotation speed and the tool traverse speed were very important parameters not only in controlling the surface morphology, but also in improving the mechanical properties of the aluminum foams. The FSP was a very effective technology for the remarkable improvement in the mechanical properties through the cell structure control of the surface region of the aluminum foams, without any dense skin materials.