Microstructural evaluation of Al-2.5wt.%Mg- 0.7wt.%Li in as cast condition

The intention of designing of innovative engineering materials with advanced properties found its role in special purposes, such as aerospace application. The main issue has been recognized as a weight savings, stiffness development and mechanical properties. Lithium, in Al-Mg-Li alloys, plays a significant role through stimulation of precipitation hardening, increasing of Young’s modulus, stiffness, fracture toughness and enhancing corrosion resistance. Other significant alloying element such as magnesium influences strengthening effect by enhancing the precipitation of metastable δ’ (Al3Li) phase. This indirect strengthening effect is possible due to fact that magnesium reduces solubility of lithium in aluminium. While the mechanism of this indirect strengthening seems to be simple, it is not fully understood if presence of magnesium merely changes the phase stability, interfacial energy or diffusion coefficient. In order to understand magnesium role in Al-Mg-Li ternary system, Al- 2.5wt.%Mg–0.7wt.%Li was produced under laboratory conditions. Obtained results of Thermo-Calc calculations and microstructural investigation enabled valuation of solidification sequence and micro constituent’s development and/or transformation