System and process for joining dissimilar materials and solid-state interlocking joint with intermetallic interface formed thereby

Abstract

A method for connecting two dissimilar materials having different melting points is described wherein a the materials are heated together to obtain plasticization of the lower melting point material within a prefigured geometry within a first material in such a way so as to form intermetallic features within a solid state joint.

What is claimed is: 
     
         1 . A method for connecting two dissimilar materials having different melting points comprising the steps of:
 placing a first material having a higher melting point than a second material, in contact with the second material within a groove and heating said first and second materials to a temperature sufficient to plasticize said first and second materials within the groove and form an intermetallic feature therein.   
     
     
         2 . The method of  claim 1  wherein said heating is obtained by friction. 
     
     
         3 . The method of  claim 1  wherein said heating is controlled to prevent overheating. 
     
     
         4 . The method of  claim 2  wherein the heating step is performed using a friction stir welding device that extends beyond the thickness of the first material into the groove to a plunge depth greater than a thickness of the second material. 
     
     
         5 . The method of  claim 4  wherein the intermetallic feature includes at least one set of hooks. 
     
     
         6 . The method of  claim 5  wherein the intermetallic feature includes at least two sets of hooks. 
     
     
         7 . The method of  claim 4  wherein the friction stir welding tool is operated within the groove in such a position so as to contact one or both sides of the groove and form the higher temperature material into a hook. 
     
     
         8 . The method of  claim 1  wherein said groove contains nested dovetail grooves and said friction stir welding tool is plunged into to the lower of two nested dovetail grooves such that a portion of the material defining the lower groove contacts the friction stir welding tool and results in the forming at least one feature of higher melting temperature material that extend upward into the lower melting temperature material. 
     
     
         9 . A joint comprising:
 a geometric shape defined by a preformed groove in a first metal material that has been filled with a second material, the second material having a lower melting point than the first material, the second material having been plasticized and heated to both fill the preformed groove and form intermetallic containing features at the interface between the first and second materials.   
     
     
         10 . A method for joining of aluminum to steel comprising the steps of: placing a piece of steel with a surface defining a dovetail groove therein in contact with a piece of aluminum having a thickness; and friction stir welding the aluminum and the steel with a friction stir welding tool that plunges to a depth greater than the thickness of the aluminum and enters the dovetail groove so as to heat both the steel and the aluminum to a temperature sufficient to plasticize and flow the aluminum into the dovetail groove and to form intermetallic features therein. 
     
     
         11 . The method of  claim 10  wherein friction stir welding tool has a scrolled shoulder and a frustum shaped threaded and flatted pin. 
     
     
         12 . The method of  claim 11  wherein the friction stir welding is performed using a tool rotational speed between 50 and 5000 RPM and a welding speed ranging between 1-5000mm/min. 
     
     
         13 . The method of  claim 12  wherein the friction stir welding is performed using a tool rotational speed between 200 and 400 RPM and welding speed ranging between 25-50 mm/min. 
     
     
         14 . The method of  claim 12  wherein the temperature of the shoulder of the friction stir welding tool is less than the temperature of the tip of the friction stir welding tool. 
     
     
         15 . The method of  claim 12  wherein the groove is a double dovetail groove.