Dislocation/coherent twin boundary interactions: new insights from quantitative in-situ TEM tensile testing

Idrissi, Hosni;Samaee, Vahid;Schryvers, Dominique
(2019) XVIth triennal international conference on Intergranular and Interphase Boundaries in Materials (IIB2019) — Location: Paris, France (1.July.2019)

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  • Idrissi, HosniUCLouvain
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  • Samaee, VahidUniversity of Antwerp
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  • Schryvers, DominiqueUniversity of Antwerp
    Author
Abstract
Ultra-fine grained materials often exhibit an outstanding strength, but unfortunately a detrimental low ductility. One exceptional case are nano-twinned materials which combine both, high strength and ductility [1]. This is associated with the presence of twin boundaries (TBs) though the underlying mechanisms of increased ductility are still not fully understood. Efforts have been devoted in the past to investigate dislocation-TB interactions using conventional static and dynamic TEM, MD simulations and more recently quantitative in-situ compression of pillars inside SEM and TEM [2]. However, tracking the intrinsic dislocation/TB mechanisms with quantitative in-situ TEM tensile testing remains absent in the literature. In this study, very clean small bi-crystal Ni samples with preselected single {111} coherent TB (CTB) have been prepared using an original preparation method [3], see Fig. 1a. These samples were deformed in tension in-situ using the PI-95 TEM picoindenter holder and the Push-to-Pull (PTP) device (Bruker.Inc), see Fig. 1b. The interactions between dislocations nucleated from single arm sources with the CTB have been observed and quantified in-situ. For screw dislocations interacting with the CTB, the results revealed transition from slip transmission across the CTB to dislocation absorption inside the boundary. The absorption process involves the dissociation of the incoming screw dislocations into pairs of twinning/antitwinning dislocations that glide in the same direction leading to CTB sliding. Image force of the CTB was measured by observing repulsive interactions between non-screw dislocations with the CTB. Finally, fracture of the sample at steps at TB was observed. The method used here open windows for more accurate characterization of the fundamental mechanisms controlling the interaction between dislocations and other types of GBs.
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Idrissi, H., Samaee, V., & Schryvers, D. (2019). Dislocation/coherent twin boundary interactions: new insights from quantitative in-situ TEM tensile testing. Book of abstracts - IIB 2019, p. 81. https://hdl.handle.net/2078.5/223972