Abstract: A wire arc additive manufacturing hybrid interlayer high speed friction (WAAM-HSF) approach is proposed to improve the performance of wire arc additive manufacturing (WAAM) components. The effect of WAAM and WAAM-HSF on the microstructure and mechanical properties of thin-walled aluminium alloy components was investigated using 1.2 mm diameter 4047 Al-Si wire using the WAAM-HSF method. The results show that the microstructures of the WAAM and WAAM-HSF components contain a large number of columnar dendrites. Compared to WAAM, the microstructure of WAAM-HSF components is significantly finer. At the same time, the grain distribution tends to be the same for the different processes, i.e. the grain diameter decreases from the top to the bottom in both thin walls. Grain refinement is achieved by disrupting the growth of epitaxial crystals. Compared to WAAM, the average elongation at break of WAAM-HSF components is reduced by 5%, but the average microhardness and average tensile strength of WAAM-HSF components are increased by 9.96 HV and 17 MPa, respectively.