Rev.Adv.Mater.Sci. (RAMS)
No 1, Vol. 18, 2008, pages 61-65


Mihai Stoica, Khalil Hajlaoui, Jayanta Das, Jürgen Eckert and Alain Reza Yavari


Fe-based alloys able to form magnetic bulk metallic glasses (BMGs) are of the type transition metal - metalloid and often contain 5 or more elements. Usually, the metalloid content is around 20 at.%. Very recently, the Fe66Nb4B30 alloy was found to be able to form BMG by copper mold casting, despite its high metalloid content. Before casting, the arc-melted master alloy was cleaned by fluxing with B2O3. The BMGs of this composition can be prepared in rod-shape and the maximum diameter for which the alloy is still amorphous is 2 mm. Several compositions with boron contents around 30 at.% or even higher were calculated since 1993 as possible compositions of the remaining amorphous matrix after the first stage of nanocrystallization of Finemet-type Fe77Si14B9 glassy ribbons with 0.5 to 1 at.% Cu and a few percent Nb addition. Melt-spun ribbons of all calculated compositions were found to be glassy. The composition of the ternary Fe-based BMG investigated in the present study resulted as an optimization of all possibilities. The alloy is ferromagnetic with a Curie temperature Tc = 550K, a glass transition temperature Tg = 845K, a crystallization temperature Tx = 876K, a liquidus temperature Tliq = 1530K and a mechanical strength of 4 GPa. The as-cast samples show a very low coercivity of 1.5 A/m, and a saturation of around 1 T.

full paper (pdf, 74 Kb)