The equilibrium shape of liquid inclusions in a crystalline matrix is a direct measure of the orientation dependence, or anisotropy, of the liquid/solid interfacial energy. In this work we have used diffraction contrast imaging in TEM to observe the shape of nanoscale liquid Pb inclusions in a solid Al matrix as a function of temperature. While a previous investigation reported a highly anisotropy equilibrium shape [1], more recent work showed that the inclusion shape depends on size, temperature and thermal history [2-4]. Here we report on a new method to make accurate automated measurements of these particle shapes during in-situ heating above the melting point of the inclusions.
Fig.l shows a typical bright field image of an array of liquid Pb inclusions in a solid Al matrix recorded at temperature during in-situ heating to 423°C. Under these two-beam diffraction conditions, particles are visible by absorption contrast and appear dark on a light background.