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Bainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C (depending on alloy content). [1] First described by E. S. Davenport and Edgar Bain, [2] [3] it is one of the products that may form when austenite (the face-centered cubic crystal structure of iron) is cooled past a temperature where it is no longer thermodynamically stable with respect to ferrite ...
Martensite in AISI 4140 steel 0.35% carbon steel, water-quenched from 870 °C. Martensite is a very hard form of steel crystalline structure. It is named after German metallurgist Adolf Martens. By analogy the term can also refer to any crystal structure that is formed by diffusionless transformation. [1]
As a result of the transformation, the microconstituents, pearlite and bainite, form; pearlite forms at higher temperatures and bainite at lower. TTT diagram of isothermal transformations of a hypoeutectoid carbon steel; showing the main components obtained when cooling the steel and its relation with the Fe-C phase diagram of carbon steels.
Even faster, and fine pearlite will form. If cooled even faster, bainite will form, with more complete bainite transformation occurring depending on the time held above martensite start Ms. Similarly, these microstructures will also form, if cooled to a specific temperature and then held there for a certain time. [17]
The steel is then removed from the bath before any bainite can form, and then is allowed to air-cool, turning it into martensite. The interruption in cooling allows much of the internal stresses to relax before the martensite forms, decreasing the brittleness of the steel.
The structures form due to the precipitation of a single crystal phase into two separate phases. In this way, the Widmanstätten transformation differs from other transformations, such as a martensite or ferrite transformation. The structures form at very precise angles, which may vary depending on the arrangement of the crystal lattices.
These highly finished stones often had mythical or spiritual shapes that showed through these stones. Hinting at the possibility that these bannerstones could serve more of a cultural purpose than just proof of transactions. These symbols take form of Algonkin symbolism and when taking a look at the pictographic records they match up quite well ...
Eutectoid steel can in principle be transformed completely into pearlite; hypoeutectoid steels can also be completely pearlitic if transformed at a temperature below the normal eutectoid. [6] [7] Pearlite can be hard and strong but is not particularly tough. It can be wear-resistant because of a strong lamellar network of ferrite and cementite.