Effect of Low Frequency Mechanical Vibration on Structure and Properties of Al-20% Si Alloy

The effect of vibrations alone or in combination with the modifiers on structure and properties of Al-20% Si alloy was studied. Particular attention was paid to the possibility of refinement of both primary and eutectic silicon at the same time. The results showed that considerable refinement of primary silicon was attained with the application of vibrations at lower amplitudes, while some of the crystals were similar to that of unvibrated alloy. With increasing intensity of vibration, the primary silicon became smaller in size and had regular geometric shape. On both cases the eutectic silicon was partially modified, while lamellar nature still persist. At the same time, this improvement in the structure showed better result in mechanical properties. Besides, higher wear resistance was noticed at 0.2 mm amplitude, while lower values were obtained at 1.0 mm amplitude. On the other hand, the results of the P-treated vibrated alloys showed that the primary silicon crystals were fine and with regular geometric shape, while the eutectic silicon was partially coarse At the same time, the silicon crystals were often surrounded with a Al. The results of the Sr - vibrated alloys showed that the primary silicon crystals became smaller in size and more rounded and its distribution was more uniform. At the same time, the lamellar eutectic silicon had completely disappeared and the eutectic Si was fully modified. Also, the mechanical properties of P-vibrated alloys showed better results than these of Sr-vibrated alloys, while both alloys showed higher wear resistance at 0.2 mm amplitude compared with unvibrated treated alloys.