Coarsening of cuboidal Al₃Sc precipitates in an Al–Mg–Sc alloy

Abstract

The coarsening of {001}-faceted cuboidal Al 3 Sc precipitates in an Al-Mg-Sc alloy during ageing at 698, 723 and 748 K have been examined by transmission electron microscopy and electrical resistivity. Application of the theory of Kuehmann and Voorhees for coarsening of second-phase precipitates in ternary systems, generalized to any centro-symmetric precipitates, has enabled independent derivation of the {001} interface energy without assuming values of the diffusivity of solute atoms (Sc and Mg) in the Al matrix. The {001} interface energy is estimated as 0.19 J/m 2 , which is excellent agreement with the value of 0.192 J/m2 obtained using the first-principles calculation method. The sphere-to-cuboidal shape change of the Al 3 Sc precipitate during ageing is discussed by means of a simple energy consideration.

Coarsening of δ-Ni2Si precipitates in a Cu–Ni–Si alloy

“…They applied the generalized KV theory to the experimental data on the coarsening of spherical, {001}-faceted cuboidal and {111}-faceted octahedral Co, Fe and Co-Fe precipitates with a face-centered cubic structure in a Cu-Co alloy, a Cu-Fe alloy and three Cu-Co-Fe alloys with different Co and Fe contents during ageing at 873 to 973 K, and then estimated the energies for sphere, {001} and {111} interfaces. Recently, we have examined the Ostwald ripening of {001}-faceted cuboidal Al 3 Sc precipitates in an Al-1wt%Mg-0.27wt%Sc alloy aged at 698, 723 and 748 K from measurements of the precipitates size by transmission electron microscopy (TEM) and the solute concentration in the Al matrix by electrical resistivity [11]. By applying the generalized KV theory to the coarsening data, the {001} interface energy were obtained without assuming values of the diffusivity of solute atoms in the matrix.…”

Effects of Sc and Zr Addition on Microstructure and Mechanical Properties of AA5182

“…The improvement in the grain refinement effect is explained by the presence of Mg and other components. The solid solubility of Sc and Zr in Al matrix was reduced, which led to more primary Al 3 (Sc x Zr 1−x ) dispersoids being precipitated [ 29 , 30 ]. The nucleation rate increased during casting, which made the addition of 0.1% Sc and 0.1% effective for refinement of AA5182 grains.…”