Role of Texture and Microstructural Developments in the Forming Limit Diagrams of Family of Interstitial Free Steels

Forming limit diagrams (FLDs) are widely used in sheet metal industries to assess formability. These are graphical representations of major and minor strains on a 2-D plot separating safe and unsafe regions. Limiting strains were measured by digital image correlation (DIC) technique. In the present work, microstructure evolution and forming behavior of family of interstitial free steels: interstitial free (IF) and interstitial free-high strength (IF-HS) grades have been investigated. Both experimental and finite element (FE) simulated FLDs indicated higher formability for IF steel. Microstructural developments affect forming limits and influence forming limit diagrams. Evolving microstructure during forming was studied by texture developments using x-ray diffraction (XRD) and in grain average misorientation developments using electron backscattered diffraction (EBSD) techniques as a function of strain and strain paths. Estimated microstructural parameters revealed that the enhanced formability of IF steel was due to the presence of strong gamma-fiber (ND//< 111 >) recrystallization texture and corresponding absence of theta-fiber (ND// < 100 >). On the contrary, IF-HS steel showed the abundant theta-fiber component and hence decreased formability.

Automated summary

The study focused on the microstructure evolution and forming behavior of interstitial free steels, showing that IF steel has higher formability compared to IF-HS steel. Microstructural developments play a crucial role in affecting forming limits and influencing forming limit diagrams.