Metal foams - A novel field of metallurgy

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.