Development of dislocation substructures was characterized in an aluminum killed deep drawing quality steel at four different plane strain deformations. At and above 20 % reduction, the most significant substructural feature was micro bands (MBs). MBs appeared as paired dislocation walls of 0.2-0.4 mm thickness and were always at an angle of approximately 37°with rolling direction (RD). As the traces of the MBs were more than 5°of {110} and {112}, closed packed planes of the bcc system,-they were termed as first generation 1) or non-crystallographic using the convention 16) commonly used in fcc metals. Other than the pre-deformation high angle boundaries, MBs were the only feature with large enough misorientations necessary for optical visibility. At least for the range of strain and strain path used in the present study, the first generation MBs can be considered as the so-called grain interior strain localizations. Relative presence and effectiveness of MBs were quantified in different microtexture components from the MB spacings along TD (l) and the average misorientation across MBs (q MB ) and these appear to determine the stored energies of different microtexture components.KEY WORDS: dislocation substructure; deep drawing quality steels; grain interior strain localizations; micro band; stored energy. Table 1. Chemical composition (in wt%) of aluminum killed DDQ steel used in the present study.

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This work aims at predicting the forming limit strains of welded blanks using a thickness gradient-based necking criterion. In order to reduce the complexity and synergistic effect of tailor-welded blank (TWB) parameters, the same material and thickness sheets are considered for the entire work. The forming limit curve (FLC) of welded blanks for varied weld conditions -namely, weld orientation and location -are predicted by simulating the limit dome height (LDH) test using PAM-STAMP (ESI Group, PAM System International), a finite element code. The un-welded blank and TWB FLCs thus predicted by the thickness gradientbased necking criterion are compared with the experimental FLCs obtained by LDH test. Dome height at failure and failure location data of TWBs from experiments and prediction are also compared for varied weld conditions. It is found from the analyses that limit strain predictions correlate well (less than five per cent error) with the experimental results in the drawing region of the forming limit diagram, with the stretching region showing considerable difference. Dome height at failure and failure location prediction correlate well with those of experimental observation in most of the cases. In a few TWB cases, where considerable difference in limit strains are seen, predicted dome height at failure values deviates from experimental results.

AISI 316L austenitic stainless steel was deformed at different strain and strain paths. The twin boundaries in the deformed microstructure had two possible origins: decay of original annealing twins and generation of deformation twins. Assuming that rotations of grains, specifically grains on both sides of a twin boundary, are responsible for the twin decay, a simple model was proposed to bring out the domain of relative twin generation. A biaxial strain path, in general, was associated with strong twin generation -an association or dependency linked to the texture estimated values of Taylor factor. Formation of strain induced martensite was also observed to be strain and strain path dependent and was more in biaxial strain path.