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Mechanical alloying ͑MA͒ of blended elemental powder mixtures of Fe 42 Zr 10 X 28 B 20 ͑X = Al, Co, Ge, Mn, Ni, and Sn͒ was carried out to determine their glass-forming ability ͑GFA͒ ͑as determined by the time required to form the amorphous phase͒. During milling, amorphization was achieved in systems with X = Al, Ge, or Ni, but not in the other systems. The GFA could be correlated with the total number of intermetallics present in the constituent binary phase diagrams. Thus, this work offers the equilibrium phase diagram as a predictive tool to determine if amorphization can be achieved by the MA method.

Mechanical alloying of a number of blended elemental powders of Fe-based alloy systems containing four or five components was undertaken to determine if amorphous phases could be produced and also to compare the glass-forming ability achieved by mechanical alloying and that obtained by solidification-processing methods. Amorphous phase formation was achieved in all the alloy systems investigated, the time for the amorphous phase formation being a function of the glass-forming ability of the alloy system investigated. However, in some alloy systems it was noted that on milling, beyond the time required for the formation of the amorphous phase, the amorphous phase started to crystallize, a phenomenon designated as mechanical crystallization. The present paper specifically discusses the results of mechanical crystallization obtained in the Fe 42 Ge 28 Zr 10 B 20 and Fe 42 Ni 28 Zr 10 C 10 B 10 alloy systems as representatives of the typical quaternary and quinary ͑five-component͒ systems, respectively. In the case of the quaternary system, mechanical crystallization led to the formation of a supersaturated solid solution of all the solute elements in Fe, while in the quinary system, a mixture of the solid solution and intermetallic phases has formed. The possible reasons for mechanical crystallization and the reasons for the differences in the behavior of the quaternary and quinary systems are discussed.

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Rapid solidification processing of metallic melts has been traditionally employed to synthesize metallic glasses in several alloy systems. However, in recent years, solid-state processing methods, and more specifically, mechanical alloying, have become popular methods to synthesize glassy phases in metallic alloy systems. Although a large number of criteria have been developed to identify alloy compositions that can be solidified into the glassy state, very few attempts have been made to predict the glass-forming ability by solid-state processing methods. To evaluate if some clear criteria could be developed to predict glass formation by solid-state processing methods and to understand the mechanism of glass formation, mechanical alloying of powder blends was conducted on several Fe-based alloy systems. Three different aspects of glass formation are specifically discussed in this paper. One is the development of a criterion for identifying glass-forming systems from phase diagram features, the second is the process of mechanical crystallization (formation of a crystalline phase on continued milling of the amorphous powders obtained by mechanical alloying), and the third is the novel phenomenon of lattice contraction during amorphization. It was shown that the conditions under which a glassy phase is formed by mechanical alloying are different from the solidification methods.