Metal foams - A novel field of metallurgy

Abstract

Metal foams cellular metals have gained an important role in the field of metallurgy, though barely a few decades old. Generally, there are three stages of matter: solid, liquid gaseous. Cellular metals or metal foams belong to the solid state. In solid metals defect like blow holes are undesirable. Even a single blow hole drastically reduces the strength of metals or alloys. Whiskers and a single crystal are defect free and possess very high strength but their manufacturing and processing cost are very high. In contrast, cellular metals or metal foams are full of holes but provides unique combination of properties allowing them for much application where solid metals fail. The holes (cells) in cellular metals or metal foams are either interconnected or closed. The unique combination of apparently contradictories properties in foams or cellular metals can not be obtained in one conventional material. For example, ultra low density, high stiffness, and the capacity to absorb crash energy, low thermal conductivity, low magnetic permeability and good vibration damping capacity can not be obtained in one conventional material. Cellular/foam metals thus find applications where several of these functions can be combined.