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D. Canelo Yubero, G. Requena, C. Poletti, F. Warchomicka, H.P. Degischer:
"Load partition and microstructural evolution during hot deformation of Ti-alloys";
Talk: Metallkunde Kolloquium Lech Arlberg, Lech; 04-11-2011 - 04-13-2011.

Synchrotron High Energy Diffraction has become an essential tool to study either the averaged internal stresses in the bulk or the microstructural changes with time of multiphase materials. The high penetration of the beam, its high flux and short acquisition times allow to study in situ the evolution of phases. The present work shows in situ investigations using this technique to follow the evolution of both internal strains and microstructure during tensile tests of Ti6Al6V2Sn (Ti662) at different temperatures. Ti662 alloys were produced by means of two processing routes, i.e., powder metallurgy (PM) and ingot (ING). PM material exhibits lamellar microstructure and the ING material has globular microstructure as a result of pre-forging. In the load direction, strains in α-phase are always higher compared with those in the β-phase. For the PM material, α-phase shows maximum strains at the maximum tensile stress and subsequently softens due to damage, while the ING material exhibits plastification once the maximum tensile stress is reached. The orthogonal direction exhibits the Poisson´s effect. The microstructure is analyzed by processing the Debye Scherrer rings for different crystallographic planes of the α and β phases. The PM material exhibits subgrain formation in the β-phase, observed as a spreading of the spots. Rotation of α-phase can be determined by a splitting of the spots. In ING samples this effect is not observable due to the fine microstructure. EBSD before and after the tensile tests confirm these microstructural changes.