Effect of the aging time on the microstructure of al-2%li-l%hf alloys

In this article, the effect of aging time in Al-Li-Hf alloy was studied. The samples were homogenized at 600°c and aged from 0.166 to lOOh at 190°c in thermal oil. According to scanning electron microscope (SEM) images, the effect of aging in the intermetalic precipitates changes its morphology as well as composition. For as cast alloys small Hf-Li precipitates with high Hf content exist. When considering aging samples the size precipitates increases, as does Hf content, from 30.74% for lh to 59.85% for 100 h. For an aging time of 100 h, the microhardness Vickers show better values which can be attributed to the Hf-Li solubility into the Al matrix to the point where their precipitation of intermetalic precipites and further cause changes in the dendritic arm spacing.