Apparatus and process for joining homogeneous and heterogeneous materials with customized interface properties

A method for joining of two or more weldable or non-weldable materials by using a friction stir spot welding, the method comprising steps of:

• creating a cavity at a centre of overlapped welding surface of a first material and a second material by removing a portion of predefined geometry therefrom at least one of the first and the second materials to form a joint region;
• adding either reinforcement or an alloying element or combination of both into said created cavity in the joint region;
• penetrating a tapered cylindrical filler material with a similar geometry design as that of said cavity in the joint region by rotating said tapered cylindrical filler material in combination with compressive force thereto;
• interlocking the tapered cylindrical filler material with at least one of the first and second materials that is weldable with the filler material to form an inter-material bond;
• welding the first material with the second material by filling the cavity formed in the joint region with the tapered cylindrical filler material;
• and
• generating a composition structure at the weld interface with customized interface material properties.