Improvement of microstructure and fatigue performance of wire-arc additive manufactured 4043 aluminum alloy assisted by interlayer friction stir processing

•The interlayer FSP was firstly employed to assist the WAAM Al-Si alloy, and eliminate the porosity and coarse dendrite in the WAAM components.•The WAAM + interlayer FSP hybrid additive manufacturing significantly improves the ductility and fatigue performance of WAAM components.•The mechanism of the improved fatigue performance correlated with microstructure developed during WAAM + interlayer FSP process is discussed and clarified.