<p>Twin-roll casting (TRC) is a process capable of producing aluminum sheets at significantly reduced cost. High-quality aluminum sheets as critical raw materials of the battery aluminum foil have become increasingly important in ensuring both performance and reliability. This study investigated the second phases and their formation mechanism in a 1060 aluminum alloy sheet processed by TRC and followed by annealing treatment. The results show that the microstructure of the TRC aluminum alloy is composed of α-Al grains, Fe-containing intermetallic phases, and Al₉Si phase. After annealing treatment, the α-Al grains exhibit a sharply increase in size, while the second phase particles show a reduction in average size, with an increased number density and a more homogeneous distribution. The annealing process partially dissolves the second phases and causes the transformation of some Fe-containing intermetallic compounds (FIMCs), leading to the growth of α-Al grains and the decrease of low angle boundaries. Finally, the annealed samples exhibit a decrease in tensile strength and an increase in elongation compared with the TRC aluminum alloy. It is found that both coarsen FIMCs and their inhomogeneous distribution tend to cause localized strain-concentration regions, thereby, promoting crack initiation.</p>