Eutectic reaction and microstructural characteristics of Al (Li)-Mg2Si alloys

Thermal analysis, directional solidification and metallographic techniques were applied to investigate the pseudobinary eutectic reaction process and the microstructural characteristics of Al(Li)-Mg2Si alloys. It was demonstrated that the eutectic reaction curve for L ⇔ Al(Li) + Mg2Si in the Al(Li)-Mg-Si system moves to the Al-rich corner with the increase of Li additions. The pseudobinary eutectic point with the highest melting temperature and null temperature range of solidification (Δ T) and the ternary eutectic point for L ⇔ Al(Li) + Mg2Si + Si all move towards the Si-rich direction. Li additions widen the range of yielding binary eutectic of Al(Li)-Mg2Si and depress the appearing of ternary eutectic efficiently. Al(Li)-Mg2Si eutectic alloys have the best aligned structure when the directional solidification occurs with a ΔT = 0. The Mg2Si phase has a diversity of morphologies such as rod-like, crossed and rooftop-like. These various morphologies has the same preferred growth direction, i.e. [100].