Abstract: A method for welding ferrous alloys to aluminum alloys or refractory metals includes the step of coating the portion of the ferrous alloy to be welded with an intermediate metal compound or element such as gold alloy or silver. An accelerated particle beam is directed at the area to be welded, and is defocused so that approximately one third of the beam energy falls on higher melting point metal, while the remainder of the beam energy is directed to the portion of the lower melting point material adjacent to the weld line and subsequently melting it. The intermediate metal compound or element dissolves in the metal alloy having the lower melting point. As the melted alloy solidifies, the intermediate compound or element precipitates out of solution and diffuses to the interface of the alloy having the higher melting point. The diffused layer bonds to the higher melting point metal, to effect a metallurgical bond.