The Role of Diffusion Accommodation and Phase Boundary Wetting in the Deformation Behaviour of Ultrafine Grained Sn-Pb Eutectic
Mechanical properties, microstructure of the Sn–38wt. %Pb eutectic and the development of deformation - induced diffusion processes on interphase boundaries (IB) were investigated. Experiments were carried out both in deformed and annealed states of eutectic using micro- and nanoindentation, SEM, AFM and optical microscopy techniques. It was found that the deformation of the annealed alloy is localized at the Pb/Sn interphase boundaries and occurs by grain boundary sliding (GBS) accompanied by sintering micropore processes under the action of the capillary forces on the Pb/Sn IB. During severe plastic deformation of Sn-Pb eutectic phase transition in the Sn grain boundary occurs. This deformation-induced process takes place due to the wetting of tin with Pb. These diffusion accommodation processes (sintering and wetting) are facilitated by the low values of the Pb/Sn interphase energy (0.07 J/m2). Wetting is thermodynamically favourable because the condition γgb > 2 γib is satisfied and it is also kinetically allowed due to the relatively high homologous temperature (> 0.5•Tm). The obtained values of the nanohardness and elastic modulus evidence that the IBs in the Sn–Pb eutectic have to be considered as a separate quasi-phase with its own properties.
Andreas Öchsner, Graeme E. Murch, Ali Shokuhfar and João M.P.Q. Delgado
F. Muktepavela and R. Zabels, "The Role of Diffusion Accommodation and Phase Boundary Wetting in the Deformation Behaviour of Ultrafine Grained Sn-Pb Eutectic", Defect and Diffusion Forum, Vols. 297-301, pp. 1002-1009, 2010