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Twinning-Induced Plasticity steel which is also known as TWIP steel is a class of austenitic steels which can deform by both glide of individual dislocations and mechanical twinning on the γ<1 1 >γ system.〔Harshad Kumar Dharamshi Hansraj Bhadeshia, Sir Robert Honeycombe, ''Steels, Microstructure and Properties'', Third edition, Butterworth-Heinemann publications, Great Britain, p 229. ISBN 0-7506-8084-9〕 They have outstanding mechanical properties at room temperature combining high strength (ultimate tensile strength of up to 800 MPa) and ductility (elongation to failure up to 100%) based on a high work-hardening capacity. TWIP steels have mostly high content in Mn (above 20% in weight %) and small additions of elements such C (<1 wt.%), Si (<3 wt.%), or Al (<3 wt.%). The steels have low stacking fault energy (between 20 and 40 mJ/m2]) at room temperature. Although the details of the mechanisms controlling strain-hardening in TWIP steels are still unclear, the high strain-hardening is commonly attributed to the reduction of the dislocation mean free path with the increasing fraction of deformation twins as these are considered to be strong obstacles to dislocation glide. Therefore, a quantitative study of deformation twinning in TWIP steels is critical to understand their strain-hardening mechanisms and mechanical properties. Deformation twinning can be considered as a nucleation and growth process. Twin growth is assumed to proceed by co-operative movement of Shockley partials on subsequent planes. == History == First steel based on plasticity induced by mechanical twinning was found in 1998 which had strength of 800 MPa with a total elongation of above 85%.〔Oliver Grässel and Georg Frommeyer, ''Effect of martensitic phase transformation and deformation twinning on mechanical properties of Fe–Mn–Si–Al steels'', Material Science and Technology, Vol. 14 (1998) No. 12, pp. 1213-1216. 〕 These values vary with deformation temperature, strain rate and chemical composition.〔Georg Frommeyer, Udo Brüx and Peter Neumann, ''Supra-Ductile and High-Strength Manganese-TRIP/TWIP Steels for High Energy Absorption Purposes'', ISIJ International, Vol. 43 (2003) pp. 438-446.〕〔Oliver Grässel, Lars Krüger, Georg Frommeyer and Lothar Werner Meyer, ''High Strength Fe-Mn-(Al,Si) TRIP/TWIP Steels Development -Properties-Application'', International Journal of Plasticity, Vol. 16 (2000), pp. 1391-1409. 〕 Researchers have shown that increased work hardening attributed to the partitioning of the austenite grains is the main contributing factor to the overall elongation of TWIP steels in which the mechanical strain of twinning have a rather small contribution.〔Bo Qin and Harshad Kumar Dharamshi Hansraj Bhadeshia, ''Plastic strain due to twinning in austenitic TWIP steels'', Materials Science and Technology, Vol. 24 (2008) No. 8, pp. 969-973. 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「TWIP steel」の詳細全文を読む スポンサード リンク
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