The influence of transformation temperature on microtexture development associated with a precipitation at b/b grain boundaries (GB) in the near-b Ti17 alloy was studied using electron backscatter diffraction and considering isothermal treatments. For the alloy studied and the temperature range considered, decreasing the transformation temperature decreased the local microtexture strength within each prior b grain because of a larger number of a WGB colonies (standing for a Widmanstätten GB) formed per b grain, each colony increasing by one the number of a orientations inside each prior b grain. This larger number of a WGB colonies was a consequence of faster formation along b/b GB of their precursors, the allotriomorphic a GB grains (standing for a-GB) at lower transformation temperatures, as evidenced by detailed examination of the first stages of a GB formation. a GB crystallographic orientations frequently followed a variant selection (VS) criterion based on the alignment of (0 1 1)b//(0 0 0 1)a GB //(0 1 1)b. From a statistically relevant number of observations, VS was found to be more frequent at a lower transformation duration and a lower temperature, but the effect was not significant enough to influence the final a microtexture, considered at the scale of one prior b grain. a GB grains that followed the VS criterion emitted two a WGB colonies on either side of the b/b GB more frequently than those with no particular orientation.

A new method called ALGrId (Anti-Leak GRain IDentification) is proposed for the detection of sub-grains beyond the relative angular resolution of Electron Backscatter Diffraction maps. It does not use any additional information such as Kikuchi Pattern Quality map nor need data filtering. It uses a modified Dijkstra algorithm which seeks the continuous set of boundaries having the highest average disorientation angle.

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Influence of chemical composition (C, Mn and Nb) and soaking temperature on the evolution of austenite grain size from a cold-rolled microstructure was studied on several Advanced High Strength Steels. A wide range of soaking temperatures was used to perform the heat treatments. Characterization of prior austenite grain size from the annealed samples using optical and confocal microscopes, Scanning Electron Microscope and Electron Back-Scattered Diffraction. Comparison of different methods was done to validate the methodology and the results were quite satisfactory. Concomitant effects of Manganese, Niobium, Carbon and of soaking temperature on the prior austenite grain size were analyzed and discussed. Important effect of Mn and Nb was underlined.

Abstract.Composite materials present interesting mechanical properties. The metal provides the toughness and the particles are adding elastic stiffness, strength, hardness and wear resistance. High energy X-ray diffraction has been used to characterize the microstructure evolution of two types of MMCs (titanium and steel matrix) reinforced with TiC particles. Evolutions of mass fraction and mean cell parameters shows the effect of reinforcement on the kinetics and mechanical state of the final composites.

A steel containing Fe-0.2C-2Mn-Si-Al was annealed using intercritical Q&P cycles. Quenching temperature and partitioning time at 440°C was varied. Analysis of microstructure evolution during such Q&P treatments was performed using different characterization tools: FEG-SEM, EBSD, dilatometer and saturation magnetization measurements. Especially, phenomena taking place during partitioning were investigated. The microstructure was analyzed at the end of soaking, before and after partitioning and at the end of the annealing cycle. It was found that bainite transformation happens during partitioning and has a significant effect on the final retained austenite fraction. Quenching temperature has an important effect on both martensitic transformation during cooling and subsequent bainite transformation during partitioning.

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