Effect of solute silicon on hydrogen precipitation in aluminum

We have measured the hydrogen behavior in aluminum specimens containing a thin Al-Si alloy layer that was formed by implanting 30- or 78-keV silicon ions. The aim is to see any effect of the layer on the hydrogen precipitation. For the purpose, 30-keV hydrogen ions were implanted into the pure aluminum region far beyond the alloy layer to a dose of 1×10¹⁷ H/cm² at a temperature of 300 K. After the hydrogen implantation, the depth profile and thermal behavior of hydrogen were measured by the elastic recoil detection (ERD) method. When hydrogen is implanted into pure aluminum metal at 300 K, hydrogen is not retained in the sample. On the contrary hydrogen was trapped in the pure aluminum region behind the Al-Si layer formed by implanting Si ions to a dose as low as 3×10¹⁴ Si/cm². The observed fact shows that the Al-Si layer influences the hydrogen trapping even in the pure aluminum region that contains no silicon. That is, the presence of the Al-Si thin layer in a near surface region obstructs the annihilation of vacancies formed by hydrogen itself in the pure aluminum region, as was proved by the hydrogen thermal behavior experiment