Microstructures of rapidly solidified and extruded Al-Pb alloys

Abstract

Hypermonotectic Al-Pb alloys have been rapidly solidified by a melt spinning device and the resultant ribbon-shaped alloys were consolidated by a combination of vacuum hot-press and hot-extrusion. The microstructures of these alloy have been investigated by TEM observations. In the melt-spun alloys a bimodal distribution of Pb particles which are classified into "corse" and "fine" ones having a mean diameter of 50 and 10nm, respectively, are shown. These Pb particles have a truncated octahedral shape surrounded with {100} and {111} facets, and indicate a cube-cube crystallographic orientation relationship with the matrix. The ratiof surface energy of {111} to that of {100} facets of solid Pb embedded in solid Al changes from the theoretical value of 1.15 to 1 with increasing in the size of Pb particles. Hot-extrusion leads the "fine" Pb particles to enlarge and breaks the dependence of anisotropy of the surface energy on the Pb particle size.