The microstructure of Fe implanted with up to 50 at.% C was found to consist of hexagonal iron carbide precipitates oriented with respect to the Fe matrix. For higher C concentrations, an amorphous phase forms. This concentration dependence is explained in terms of the lattice structure of the iron carbide. In Ti-implanted Fe, substitutional Ti was found in the bcc Fe lattice for concentrations ≤ 15 at.% Ti. The work of others suggests that amorphous phases form for ≥ 33 at.% Ti. These results are discussed in terms of concentration boundaries of the ternary Fe(Ti,C) amorphous phase.
Ion beam alloying methods are currently being used to form metastable alloys , both for fundamental investigations of such alloys as well as for potential use to improve physical properties of components . An important consideration in metal alloys is what phase will form upon implantation; one aspect of this question is to determine when amorphous phases will form. Rules are currently being advanced to predict alloy systems which will yield amorphous phases. By using ion irradiation and ion beam mixing as well as ion implantation, such rules can be evaluated over entire composition ranges.
To gain insight into amorphous phase formation, we have studied Fe alloys implanted with C, Ti and Ti + C. The Fe(C) alloys exhibit compound precipitation and amorphous phase formation; the precipitation and the concentrations at which the amorphous phase appears can be accounted for by considerations of the structure of the hexagonal carbide which forms. Based on conventional uses of the Fe(C) system, such alloys may be useful for improving mechanical properties by implanting C into ferrous components. Iron implanted with Ti is examined to a limited extent here, but by including ion irradiation studies by others , a more complete characterization of Fe(Ti) alloys is obtained. The microstructures of Fe(C) and Fe(Ti) are examined along with the known composition limits of amorphous Fe(Ti,C) alloys, which are important for their improved mechanical properties . Taken together, a more complete determination of amorphous phase formation in this ternary system is obtained.