Brazing is a joining process whereby a filler metal or alloy is heate to melting temperature above 450°C (842°F), or, by the traditional definition that has been used in the United States, above 800°F (425°C) and distributed between two or more close-fitting parts by capillary action. At its liquid temperature, the molten filler metal and flux interacts with a thin layer of the base metal, cooling to form a strong, sealed joint. By definition the melting temperature of the braze alloy is lower (sometimes substantially) than the melting temperature of the materials being joined. The brazed joint becomes a sandwich of different layers, each metallurgically linked to the adjacent layers. Common brazements are about 1/3 as strong as the parent materials due either to the inherent lower yield strength of the braze alloy or to the low fracture toughness of intermetallic components. To create high-strength brazes, a brazement can be annealed to homogenize the grain structure and composition (by diffusion) with that of the parent material.