Numerical Modeling of Twinning Induced Plasticity in Austenite Based Advanced High Strength Steels

Advanced manufacturing techniques make it possible to attain large deformation of material in order to obtain required shape of a product. However, one of the main reasons behind their successful implementation is having an optimum combination of strength and formability of a material. The enduring challenge of increasing these two contradictory properties simulta- neously is achieved through the invention of Advanced High Strength Steels. Advanced high strength steels cover a vast range of applications, more specifically in aerospace, automotive, and oil industry where large deformation of a material is desired to attain a specified shape and geometry of the product. Austenite based twinning induced plasticity steel lies in the sec- ond generation and has excellent strength and formability among the group of advanced high strength steels. The stress assisted phase transformation from austenite to martensite, which is known as twinning, found to be principal reason behind an enhancement of these properties. This work is aimed to investigate an elastic-plastic behavior of an austenite based steel, which undergoes slip and mechanical twinning modes of deformation. Initially, a micromechanical model of twining induced plasticity is developed using crystal plasticity theory. Then, the developed model is numerically implemented into finite element software ABAQUS through a user-defined material subroutine. Finally, finite element simulations are done for single and polycrystal austenite subjected to combined load. This replicates the complex loading condi- tion which exists in material forming processes like pipe expansion, extrusion, rolling, etc. The variation in stress-strain response, magnitude of shear strain, and volume fraction of twinned martensite are plotted and analyzed.