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

Abstract

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 α-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.