Crystalline powders of Si and Ln (Ln = Sm, Nd, Gd, Tb, Dy, Er) in the compo
sition ratio Si:Ln = 2 : 1 were mechanically alloyed in an inert atmosphere
using a laboratory ball mill. The progress of the mechanical alloying was
identified by X-ray diffraction. The amorphization reaction between Si and
Ln proceeded according to a second-order formula. The sequence of the rate
of amorphization reaction for the Si-Ln system was Sm>Gd>Tb>Nd greater than
or equal to Dy>Er. The reaction rate was affected by the crystal structure
of Ln. In the case of Gd, Tb, Dy and Er having the same structure (hexagon
al closed packed), the reaction rate was correlated to the volume ratio (V-
Ln/V-Si). In the Sm-Si system, which had the fastest MA rate, Sm has a uniq
ue structure in which triangular planes of Sm atoms overlap fourfold and wo
uld be easily attacked by Si atoms. In Nd-Si system, the rate would be affe
cted by the structure of double hexagonal closed packed of Nd. The crystall
ization of Si-Ln was studied by means of X-ray diffraction, differential th
ermal analysis and electrical resistivity measurement.