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Towards work-hardenability of Ti-6Al-4V using the α – α’ dual-phase microstructure

par Dumas, Odeline ;Malet, Loïc ;Hary, Benjamin ;Prima, Frédéric;Godet, Stéphane
Référence TMS 2020 149th Annual Meeting & Exhibition (2020-02-(23-27): San Diego - USA)
Publication Non publié, 2020-02-26

Communication à un colloque

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Résumé :

In this work, a quenching and partitioning strategy has been developed to provide insight into the possibilities to reach a work-hardening capacity very rarely reported in Ti-6Al-4V. Indeed, it was recently demonstrated that a sub-transus thermal treatment followed by water quenching could generate an  + ’ microstructure displaying a high work-hardening and a promising increase in both strength and ductility. We performed a series of ‘quenching’ treatments using several solutionizing temperatures. In such way, the volume fraction of each phase, the size, the chemistry and the interfaces of the martensite are taken as microstructural variables to decompose the peculiar work-hardenability of dual-phase Ti-6Al-4V into respective contributions. Then, annealing of the dual-phase microstructure was performed for different times to bring about the martensite decomposition involving a ‘partitioning’ of the alloying elements. Martensite was shown to be a very heterogeneous and discontinuous medium in which interfaces play a crucial role in the capacity of the material to progressively transform during the deformation and harden at a macroscopic scale. The capacity of the martensite islands to progressively decompose into an equilibrium and very fine microstructure provides a broad range of surprisingly high mechanical properties. These results completed the dual-phase microstructure comprehension and highlighted the martensite yet unknown decomposition mechanisms.