Bainite
A eutectoid transformation product of ferrite and a fine dispersion of carbide, generally formed at temperatures below 840 to 930 F (450 to 500 C): upper bainite is an aggregate containing parallel lath shape units of ferrite, produces the so called feathery appearance in optical microscopy, and is formed at temperatures above about 660 F (350 C); lower bainite consists of individual plate shape units and is formed at temperatures below about 660 F (350 C). Also, a slender, needle like (acicular) microstructure appearing in spring steel strip characterized by toughness and greater ductility than tempered Martensite. Bainite is a decomposition product of Austenite best developed at interrupted holding temperatures below those forming fine pearlite and above those giving Martensite.
