Recent experiments by Backerud and Johnson suggest that there are two regimes of activity for the grain refining of aluminum base alloys. In one, adding dissolved titanium (or other solute elements) produces better grain refinement. In the other, adding Ti produces a contrary effect, or larger grains. Most casting alloys employ significant levels of dissolved titanium. Levels of 0.1-0.15 percent Ti are common. The recent paper by Backerud suggests that lower levels of dissolved Ti should give smaller grain size. If this is true, significant cost savings may result. To test this hypothesis, and to determine the most cost-effective method of refinement, test samples of 319 alloy were cast with varying amounts of Ti and commercial grain refiners. The results do not agree with Backerud's theory. Best grain refinement was found at high concentrations of dissolved Ti and commercial grain refiner.
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