The interaction between flow and progressing solidification front is of great importance, since it occurs in all casting processes. The present paper provides a better understanding of the flow phenomena and associated complex effects on solidification in a rectangular cavity under forced flow conditions, by means of experiments and computer simulations. It is shown that the cavity-driven flow with solidification is determined by several interacting features. The variation in bulk flow velocity and initial superheat dramatically changes the macro- and microstructure, promoting grain refinement, formation of peculiar grain and dendrite morphologies, etc. In particular, twinned feathery grains are found in the structure formed under certain heat and flow conditions during solidification. Some correlations between twinned feathery morphology, flow and solidification parameters are obtained. The effect of flow vortices on progressing solidification front and their effects on structure evolution are analyzed. Finally, the quantitative correlations between microstructure, solidification and flow parameters are established.