Glass formability of ferrous- and aluminum-based structural metallic alloys

Synthesis of ferrous- and aluminum-based amorphous metals as prospective structural materials is presented and discussed in light of atomic size-composition interaction effects. The search of prospective bulk metallic glasses (BMGs) may benefit from noting that current BMG alloys can be broadly categorized into two atom size-composition classes, distinctly different from ordinary metallic glasses which can exist over a much wider atom size-composition range. The high formability of one class of BMGs is suggested to be due to the presence of a structure-reinforced network or backbone formed by tightly bound components in the undercooled liquid. For the ferrous-based BM, G alloys investigated, it is proposed that zirconium-boron and molybdenum-carbon atom pairs constitute the strong backbone structures. Although aluminum-based BMG has not been reported, the good formability of some current aluminum-glasses is suggested to be due to the presence of backbone. structures formed by transition metal-lanthanide and magnesium-copper pairs. The ferrous-based bulk metallic glasses obtained have a high reduced glass transition, temperature reaching 0.63 and large supercooled liquid region up to 100 K. These bulk metallic glasses are found to be nonferromagnetic above 160 K as well as having Vickers hardness and specific tensile strengths that far exceed those reported for steel alloys. Magnetization and susceptibility results are presented and compared with ab initio magnetic-structure calculations [D.M. Nicholson, M. Widom, Y. Wang, unpublished results]. Relevant factors on forming bulk metallic glasses are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.