Effect of titanium additions on the microstructure of DC-cast aluminium alloys

The effect of the Ti content on the solidification structures of aluminum alloys of AA3003 type was investigated. Some improved corrosion properties can be obtained from increasing the Ti contents in aluminium alloys to a level above the normal practice for grain refinement. However, increasing the Ti content above the peritectic point, 0.15%, can influence the grain refinement and cause casting difficulties. The investigation was made by both characterizing the grain structure over the width of DC-cast rolling ingots of different alloys, and by studying the solidification microstructure of Bridgman directional solidified samples, grown to simulate ingot solidification. Structure properties such as grain size, distances between secondary phases and microstructure coarsening were studied. found that with normal Ti contents in the range of 0.015%, the grain refinement is effective. However, upon larger Ti additions to levels around 0.15% the grain structure becomes coarser.