Microstructural Evaluation of Deformed AISI 316 Steel by X Ray Peak Broadening and EBSD

ANDREA KLIAUGA; MAURIZIO FERRANTE; RAÚL E. BOLMARO

Rio de Janeiro

Congreso; 17th International Microscopy Congress - IMC17; 2010

Microstructure development by plastic deformation and possible later heat treatment include dislocation accumulation, either distributed or in dense arrays, twins, grain fragmentation, etc., and their further annihilation due to recovery and recystallization processes. Many experimental techniques are useful to evaluate, with more or less accuracy, the amount and quality of such microstructural features. Among them, a very old technique, based on X-ray peak broadening measurement, has recently evolved to become a fine tool for the evaluation of dislocation densities, grain size and twin boundary presence. The technique can be considered a ?bulk? technique, in the sense that is not able to evaluate those features as field quantities but as average ones. Simultaneously, Electron Back Scattering Diffraction (EBSD) has come on age, revealing as a powerful technique to investigate, at the scale of a few tens of nanometers, the distribution of grain orientations, misorientations, phase relationships, etc.. Paradoxically, such a powerful technique still relays on complex statistical after processing for the evaluation of parameters correlated with plastic deformation and consequent dislocation storage. Because of the known inability of Transmission Electron Microscopy (TEM) to provide statistically significant information still a proper quantification is needed. The current paper shows an attempt to compare data obtained by both techniques in an AISI 316 steel deformed by various strain paths and further several heat treatments.As Received (heat treated) AISI 316 steel was deformed by Equal Channel Angular Extrusion (ECAE) by route A by 1 and 2 passes, cold rolled at 70% reduction and, this last one, heat treated 1 h at 700 C and 800 C. Fig. 1 shows the Williamson Hall plot of As Received (0X), 1X and 2X ECAPed and 70% rolled samples, from which grain sizes, twinning and dislocation densities can be evaluated [1].   EBSD experiments were performed on similar samples after careful polishing and electropolishing to eliminate surface damage. Fig. 2 shows the EBSD map of EBSD scanning of 70% Rolled, 1h 700o C Heat treated sample. Step size 0.5 µm. Fig 3 and 4 show the low angle distribution (