Effect of Cu content on the reaction growth and morphology of an Al ₁₂W compound between Al-Cu/Ti-W bilayers

The effect of Cu content on the reaction growth and morphology of the Al₁₂W phase in annealed Al-Cu/Ti-W films was directly studied by cross-section transmission electron microscopy. After heat treatment at 450°C for 30 min, spiked growths of the Al₁₂W phase penetrated into the overlying Al-0.5 wt % Cu film. In contrast, increasing Cu concentration to 1.5% in the Al film suppressed the spiked growth of the Al₁₂W phase, resulting in a smooth and discrete layer of Al₁₂W between the Al-Cu and Ti-W films. It is suggested that an increasing amount of grain boundary segregation of Cu in the Al alloy film suppressed the Al₁₂W spiked growth.