Diffusion welding or diffusion welding is a solid state welding technique used in metal-making, capable of bonding like and different metals. It works according to the principle of solid state diffusion, in which the atoms of two solid metal surfaces intermingle over time. This is typically carried out at an elevated temperature, about 50-70% of the absolute melt temperature of the materials. The diffusion bonding is generally carried out by applying a high pressure, together with a necessarily high temperature, to the materials to be welded; the technique is most commonly used to weld "sandwiches" of alternating layers of thin metal paper, and metallic wires or filaments. Currently, the diffusion bonding method is widely used in bonding high strength and refractory metals within the aerospace and nuclear industries.