Typical Microstructures of Iron-Base Alloys

This article is a pictorial representation of commonly observed microstructures in iron-base alloys (carbon and alloy steels, cast irons, tool steels, and stainless steels) that occur as a result of variations in chemical analysis and processing. It reviews a wide range of common and complex mixtures of constituents (single or combination of two phases) that are encountered in iron-base alloys and the complex structure that is observed in these microstructures. The single-phase constituents discussed in the article include austenite, ferrite, delta ferrite, cementite, various alloy carbides, graphite, martensite, and a variety of intermetallic phases, nitrides, and nonmetallic inclusions. The article further describes the two-phase constituents including, tempered martensite, pearlite, and bainite and nonmetallic inclusions in steel that consist of two or more phases.