Search

Thermal motion of two liquid lead inclusions attached to the same fixed dislocation in an Al-0.65 at% Pb alloy is studied in situ at 447 °C using transmission electron microscopy. Observations of their motion is recorded on video and analyzed frame by frame. Random oscillatory motion of the inclusions on the dislocation line occurs as a result of their mutual repulsion and their repulsion from the fixed ends of the dislocation caused by the dislocation line tension. The oscillations of the inclusions can be considered as correlated thermal motion in coupled potential wells. The effective potentials, in which the inclusions move, and the effective potential of their interactions are evaluated. It is found that the spatial correlations of the positions of the inclusions on the dislocation depend strongly on the interaction potential. The observed correlations of the positions of the inclusions suggest that they move along their averaged trajectories in a synchronous-like manner.

In situ transmission selctron microscopy is used to study dissolution of liquid single-phase Pb/Bi inclusions attached to grain boundary in an alloy of Al99.29Pb0.65Bi0.06 at temperatures of 343, 370, and 389 °C, respectively. The initial size of the inclusions was smaller than 60 nm. Dissolution of the inclusions was observed until their complete disappearance. Digitized video recordings of the process of dissolution were used to obtain the dependence of the inclusion size with time. The kinetics of the dissolution of the grain boundary inclusions can be described with a model where it is assumed that grain-boundary diffusion of Pb and Bi is the controlling mechanism. The high value (2.3 eV) of the apparent activation enthalpy of dissolution indicates that the process is likely governed by the large negative enthalpies of solubility of Pb and Bi in Al.