An assembly includes a first structural member made from a first material, such as aluminum, a second structural member made from a second material, such as magnesium, and adapted to mate and interlock with the first member, and a third structural member made from the first material to facilitate a permanent affixation between the first and second members. The second member fits within the first member and the third member fits within the second member. The second member includes at least one aperture surrounded by a protrusion, and the third member includes at least one aperture that mates and interlocks with the protrusion. A surface of the third member is exposed through the apertures of the first and second members. The first member is welded to the third member through the apertures in order to permanently affix the first and second members to one another without metallurgical altering or local welding of the second member.