Effect of Ti on the microstructure and Al–water reactivity of Al-rich alloy

• Al grains are markedly refined with Ti addition in alloys above 0.5 wt.%.
• Ti influences Al–water reaction depending on Ti contents.
• Al grain refinement promotes Al–water reaction and increases H2 yields.

Ti-bearing Al alloys (0.1–1 wt.%) were prepared using arc melting techniques. Their microstructures were investigated using XRD and SEM/EDX, and found to depend strongly on Ti contents. Al grains are columnar as Ti contents are lower, but they are refined and turn into equiaxed ones when Ti contents are higher. The particle sizes of Ga–In–Sn phase decrease with Al grain refinement. Al–water reactivities were also investigated under different water temperatures. Kinetic measurements found that Ti prohibits Al–water reaction and reduces hydrogen yields when alloys contain little Ti. However, Al reacts with water fast and hydrogen yields rise with the increase of Ti contents of alloys. Reasons concerning the variations of microstructures and Al–water reactivities with Ti additions are discussed.