Methods of joining dissimilar metals without detrimental intermetallic compounds

A method of joining a first component and a second component, the first component and the second component being made of dissimilar metals and each having a dissimilar metal interface and each with a faying surface, the first component having a lower melting temperature than the second component, the method comprising:

• smoothing the faying surface of the second component to a roughness value of Ra<0.025 μm and reducing surface oxidation of the second component to a thickness less than 2 nm before joining;
• inserting a rotating tool having one shoulder portion and one rotating probe portion into the first component, the one rotating probe portion is spaced apart from the faying surface of the second component by a standoff distance of 0.05 to 1 mm;
• rotating the rotating tool to generate a rapid friction between the second component and material of the first component rotating around the one rotating probe portion at the dissimilar metal interface, the rapid friction being sufficient to generate a layer of quasi-liquid metal and produces shear localization within the quasi-liquid metal at the dissimilar metal interface between the first component and the second component, the quasi-liquid metal being a metal in a liquid-like state at a temperature below the melting point of the first component and the second component, the quasi-liquid metal having a shear strain rate above 1×104 s−1;
• one distal end surface of the one rotating probe portion having surface features to promote rotation of the quasi-liquid metal around the one rotating probe portion;
• and
• terminating the application of the rapid friction and reducing a processing temperature of the quasi-liquid metal below a crystallization temperature of the quasi-liquid metal within 3 seconds after generation of the quasi-liquid metal and before 80% of the quasi-liquid metal has crystallized within the quasi-liquid metal thereby joining the first component and the second component along a transition layer, the transition layer having a composition corresponding to a metallic glass former composition.