Ti6Al4V is the most widely used titanium alloy [1] and comprises two phases, viz. a hexagonally closely packed α phase and a body centred cubic β phase. For the lifing prediction of the alloy components and also for the future alloy development, it is of interest to understand the role of various interfaces such as grain boundaries and inter-phase boundaries in the mechanical response of the alloy. The last ten years have seen the development of nano-mechanical testing within electron microscopes on samples prepared using focused ion beam, which has not only offered the quantitative mechanical properties but also the simultaneous imaging analysis of samples containing specific structural features [2, 3]. In this work, in-situ electron microscopy studies on miniaturised Ti6Al4V samples were used to achieve a better understanding of the plastic deformation micro-mechanisms involved. Micron-sized pillar samples were compressed in an SEM and the mechanical properties of both alpha and beta phases were evaluated, while sub-micron sized pillars were compressed in a TEM to observe the dislocation activities. The nucleation of dislocations, the yielding of the samples and the work hardening observed in the samples with different sizes will be discussed.

References:

1. Lütjering, G. and J. C. Williams (2007). Titanium, Springer.
2. Q. Yu, M. Legros, A.M. Minor, MRS Bulletin, 40.01 (2015): 62-70
3. M.W. Kapp, C. Kirchlechner, R. Pippan, G. Dehm, Journal of Materials Research, 30.6 (2015): 791-797

Figures:

Figure 1 (a) SEM images showing the microstructure of the Ti6Al4V alloy used in the current study; (b) A TEM image of a sample to be compressed in a TEM; (c) The load-displacement curve recorded during the compression of a pillar reaching the yielding and (d) the corresponding TEM image acquired during the loading showing the nucleation of the dislocation (as shown by the arrow).

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EMC Abstracts - https://emc-proceedings.com/abstract/in-situ-deformation-of-ti6al4v-in-electron-microscopes/