Quantitative Approaches to Structure Teams

A friction welded joint structure includes friction welded dissimilar first and second metallic materials. The first metallic material has a rigidity greater than the second metallic material. The angle of the first metallic material to a free edge of the first metallic material, at an end portion of a joined surface between the first and second metallic materials, is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees. A reaction layer between the first and second metallic materials is more than zero and less than or equal to 20 mum. The first metallic material is copper. The second, which has the smaller rigidity, is aluminum.