ISSUE 4/2013

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Weiss, A.; Wendler, M.; Gutte, H.; Biermann, H. High-strength cold-formable austenitic cast steel with TRIP/TWIP properties 

A new austenitic cast steel, designated as G-X4CrMnNi16 7 6 or G-4CrMnNi16 7 7, is introduced that is characterized by a relatively low austenite stability with respect to the  and ’ martensite transformations and a low stacking fault energy. These characteristics are responsible for the occurrence of TRIP/TWIP effects (TRansformation-Induced Plasticity/TWinning-Induced Plasticity) when subjected to stress. Therefore, when deformed, the deformation-induced processes of twins and /’ martensite formation accompany the dislocations glide. Due to the multiple plasticity mechanisms, the cast steel shows excellent cold-forming properties at temperatures above ambient, in spite of having a coarse dendritic microstructure. High levels of deformation by drawing and rolling are shown to be feasible without any intermediate annealing. During cold forming, the cast steel exhibits significant work hardening as /’ martensite and twins form in the structure. Through plastic pre-straining, the strength increases significantly at the expense of a moderate decrease in ductility. This allows for the manufacture of high-strength cast steels with acceptable levels of ductility in response to the demand for light components with excellent crash-relevant properties and an enhanced resistance to wear.

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