Amorphization by mechanical alloying: The role of mixtures of intermetallics

Article abstract of DOI:10.1016/0022-5088(88)90369-4

This paper reports selected results on the systematics and mechanisms of amorphization by mechanical alloying of mixtures of intermetallic compound powders. Mechanical alloying was carried out on mixtures of 'line' intermetallic compounds (i.e. those having a narrow range of homogeneity) in Cr-Ti, Mn-Ti, Cu-Ti, Fe-Ti, Co-Ti, Ni-Ti, Cu-Zr, Ni-Zr and Mn-Si. Amorphization by mechanical alloying was observed to be complete, to the resolution of X-ray diffraction, for intermetallic compound mixtures in all the above systems except Cr-Ti, which exhibited partial amorphization, and Mn-Si, which showed no amorphization. The amorphization tendencies could not be predicted from calculated enthalpies of mixing for the amorphous alloys, all of which were negative, or from calculated differences in free energy between the amorphous phase and the mixture of equilibrium intermetallic compounds. Preliminary transmission electron microscopy studies of the evolution of the amorphous phase for the system NiZr₂+Ni₁₁Zr₉→a-Ni₄₀Zr₆₀ revealed an amorphous halo-like region surrounding the transforming intermetallic particles in a amorphous matrix. Energy dispersive X-ray analysis measurements indicate that the halo-like region has a composition which falls between those of the intermetallic particle and the amorphous matrix.