Table 4: Trace elements in Al and its alloys [2].

Trace elementsConcentration (wt %)Properties

H0.0001Presence of S, Mg and Li increase the absorption of H while Si, Sn, Cu, and Be reduce it. Formation of gas porosity after solidification.
Fe and Si0.1–1.0Formation of Al3Fe and AlFeSi second phase compounds, which reduce the fatigue and fracture properties of Al alloys.
Na, Li and Ca<0.01These elements enhance the Al-Si eutectic structure resulting in higher strength properties and pressure tightness effect. Rolling might be difficult because of formation of edge cracking tendency. Li increases the strength at elevated temperatures, maintaining low density.
Ti, V, Cr, Mn0.001–0.05Cause grain refinement during solidification, retard recrystallization during deformation. Presence of Mn also acts as Fe-corrector correcting the shape of Fe bearing precipitates.
Ga0.001–0.02The corrosion behavior, etching, and brightening of some alloys are altered.