MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg-Ti ALLOY PREPARED BY MIXING Al-Ti POWDERS AND Al-Cu-Mg MELT

摘要

Al-7wt.%Ti powders with an average size of 100 mu m were used for solid-liquid mixing and near liquidus casting of TiAl3 particles reinforced Al-Cu-Mg alloy. The mixture of Al-7wt.%Ti powders and mixed salt (50%NaCl+50%KCl) was preheated at 752 degrees F (400 degrees C) and added into Al-Cu-Mg alloy melt during the casting process. The microstructural evolution of Al-Cu-Mg-Ti alloy was observed using scanning electron microscopy. The results show that the size of TiAl3 particles in Al-Cu-Mg-Ti alloy is in the range of 2 similar to 10 mu m, which is almost the same as that in Al-7wt.%Ti powders. The morphology of the TiAl3 particles changes from fine needle in Al-7wt.%Ti powders to short-rod or lump in Al-Cu-Mg-Ti alloy. After the Al-Cu-Mg-1.5Ti alloy has been remelted at 1328 degrees F (720 degrees C) for different time, the circularity factor of TiAl3 particles maintains at 0.76. With the increasing of remelting time, the average size of TiAl3 particles increases rapidly when the time is less than 15 minutes, then it increases slowly with the time increasing.