Formation of Intermetallic Compounds with the B2-type Structure upon Mechanical Alloying of Fe_(50)Al_(50-x)Si_x

摘要

X-ray diffraction and Mossbauer spectroscopy were used to study Fe_(50)Al_(50-x)Si_x powders prepared by mechanical alloying. The solid-state interaction between Fe, Al, and Si was provided by milling powder mixtures in a high-energy ball mill in an argon atmosphere. The formation of a partially ordered bcc solid solution occurs immediately upon milling. This is confirmed by the appearance of superlattice reflections typical of B2 ordering in X-ray diffraction patterns and by the presence of a singlet typical of the symmetrical surroundings of Fe atoms by nonmagnetic Al and Si atoms in the Mossbauer spectrum. Long-term milling of mixtures containing more than 25 at. percent Si leads to the formation of two phases, Fe_(50)Al_(50-x)Si_x (B2) and FeSi (B20). For the Fe_(50)Al_(50-x)Si_x mixtures with x<20 at. percent, the degree of long-range order increases, and the lattice parameter of the bcc solid solution decreases with increasing silicon content.