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TWIP

TWIP: TWinning Induced Plasticity steel
Definition:TWIP steel is characterized by the formatioin of mechanical twinnings during deformation.
Explanation:TWIP steels are a class of austenitic steels with superior mechanical properties like high strength and high formability [1,2]. TWIP steels are conventionally known for their specific energy absorption properties together with their temperature insensitive toughness properties. In TWIP steels, the mechanical twins are continuously formed during deformation. From the crystallographic point of view, the formation of twins can be interpreted as the stacking faults (→SFs) taking place on every close packed plane {111}. The stacking fault energy (→SFE) is the key factor to control the mechanical properties of austenitic steels. The TWIP steels exhibit relatively SFE (20-50 mJ m-2). During deformation, complex deformation behaviors can occur: dislocation slip, deformation twinning, and dynamic strain aging (→DSA), which result in a considerably high strain hardening.
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Fig. 1. Mechanical twinning formation during deformation in a high Mn TWIP steel, where blue color represents the boundaries of deformation twinning
SFB-Link:Within SFB761, high Mn TWIP steels are designed and intensively investigated in terms of the microstructure, deformation behavior, twinning formation features and mechanisms by means of modeling methods as well as electron backscatter diffraction (→EBSD), transmission electron microscopy, atom probe tomography (→APT) , etc.
References:[1] O. Grässel, L. Krüger, G. Frommeyer, L. W. Meyer. High strength Fe-Mn-(Al, Si) TRIP/TWIP steels development-properties-application. International Journal of Plasticity, 2000, 16: 1391-1409
[2] B. C. De Cooman, O. Kwon and K.-G. Chin. State-of-the-knowledge on TWIP steel. Materials Science and Technology, 2012, 28: 513-527