Evolution of microstructure and properties of novel aluminum-lithium alloy with different roll casting process parameters during twin-roll casting

Twin-roll casting (TRC) process combines continuous casting and rolling deformation into one process, which compensates for the solidification shrinkage of liquid metal in the roll-casting region and solves the defects caused by the addition of lithium in aluminum alloy, such as shrinkage porosity and shrinkage cavity in aluminum-lithium alloy ingots produced by traditional casting technique. In this work, the evolution of microstructure and properties of AA2099 aluminum-lithium alloy sheets fabricated with different cast-rolling speeds during TRC process was investigated in detail. The quantitative relationship between the degree of central macro-segregation and micro-segregation of the TRC slabs as well as secondary dendrite arm spacing (SDAS) and the number of non-equilibrium eutectic phase with different cast-rolling speeds was revealed. The cooling rate increases gradually with the increase of cast-rolling speeds, the dendrites will be refined and the degree of central macro-segregation relieves dramatically, and the number of non-equilibrium eutectic phases decreases significantly at relatively higher cooling rate during TRC. In addition, more alloying elements will be captured and dissolved in the a-Al matrix in a faster cooling rate, and the solid solution supersaturation of solute elements in alloys is significantly enhanced. Hence the mechanical properties of the sheets have been improved remarkably.