Friction stir welding is now well known as a solid-state welding process in particular for the assembly of aluminium alloys. We will quickly discuss the advantages of this welding process and this will lead us to the conclusion that this process can be exploited to manufacture new materials or improve their properties exploiting the large plastic deformation involved in this process. In that perspective, we have improved by a factor 100 the fatigue life of 3D printed aluminium alloys, developed new self-healing aluminium based composites or developed new NiTi reinforced aluminium that exploit the shape memory effect to deviate cracks and enhance toughness. A whole new way of thinking about material design freed from the limitations of traditional manufacturing….