Some materials exhibit a combustion event during mechanical alloying, which
results in the rapid transformation of reactants into products, while othe
rs show a slow transformation of reactants into products, In this paper, th
e continuous W + C --> WC reaction is compared to the Ti + C --> TiC combus
tion reaction. Rietveld refinement of X-ray diffraction patterns is used to
show that these particular reactions proceed through different pathways, d
etermined by crystallographic factors of the reactants. When a crystallogra
phic relationship exists between the reactants and the products, such as th
at between W and WC, the product forms slowly over a period of time. In con
trast, insertion of C into the Ti structure is associated with atomic rearr
angements within the crowded lattice planes and the subsequent catastrophic
failure of the reactant lattices results in combustion to form TiC. (C) 20
01 Academic Press.