PREPARATION OF ULTRAFINE AL-BASED QUASI-CRYSTALLINE PARTICLES BY REACTION BETWEEN NITROGEN PLASMA AND MOLTEN ALLOYS

Ultrafine icosahedral particles in the Al-Cu-Fe and Al-Pd-M (M=Cr, Mn or Fe) ternary systems and decagonal particles in the Al-Co-Ni and Al-Co-Cu systems have been found to form by the reaction between nitrogen plasma and, the prealloyed ternary alloy melts. These icosahedral and decagonal particles have a spherical morphology and their diameter is about 100 nm. The icosahedral or decagonal particle is always coexistent with B2 and/or fcc-Al particles. The formation of the quasicrystalline particles for these alloy systems is presumably because the vaporization rate ratio between Al and other solute elements is in the range of 0.0302 to 7.12. The difficulty of the elimination of the B2 and Al particles is because the icosahedral phase has rather strict stoichiometric alloy compositions and is formed through the peritectic reaction and the decagonal phase also has a narrow composition range.