Precipitation of nanogranular Ge particles in rapidly solidified Al-Si-Fe-Cr-Ge alloys

The effect of Ge addition on the microstructure and some properties of rapidly solidified Al-Si-Fe-Cr alloys was examined. In particular, the addition of 9 to 15 at% Ge to Al₅₆Si₃₀Fe₁₀Cr₄ alloy causes a change from an amorphous phase in the Ge content below about 9 at% to a mixed structure consisting of homogeneous dispersion of fine Ge solid solution particles in an amorphous matrix in the Ge content range of 9 to 15 at%. The size, volume fraction and composition of the Ce particle depend on Ge concentration in the alloys. The Ge particle in the Al₄₄Si₃₀Ge₁₂Fe₁₀Cr₄ alloy has a size of about 10 nm and homogeneously distributes in the amorphous matrix. The Al-Si-Fe-Cr-Ge alloys are characterized by high hardness numbers H_v of 680 to 910. The crystallization process and phase composition of the above-mentioned alloys in the crystallized state change with Ge content. The primary precipitation of Ge from the amorphous phase is thought to result from the complicated interaction among the constituent elements.