Tendency of metallic crystals to amorphization in the process of severe (Megaplastic) deformation

摘要

The main features of the transition of crystalline Ni_(50)Ti _(30)Hf_(20), Ti_(50)Ni_(25)Cu_(25), Zr_(50)Ni_(18)Ti_(17)Cu_(15), and Fe _(78)B_(8.5)Si_9P_(4.5) alloys with various tendencies to amorphization into an amorphous state upon melt quenching and in the course of severe deformation in Bridgman anvils have been considered. The crystalline state of these alloys has been produced using various methods of annealing. In the iron-based alloy, single-phase and two-phase crystalline states have been studied. The nickel- and titanium-based alloys after annealing were in a single-phase crystalline state; the zirconium-based alloy, in a two-phase state. It is shown that at the same degree of deformation the rates of amorphization of crystalline alloys differ substantially; namely, the single-phase crystalline titanium- and iron-based alloys amorphize easily, whereas the Zr-based alloy amorphizes only poorly, just like the two-phase iron-based alloy. It can be assumed that the tendency to deformation-induced amorphization of crystalline alloys and the corresponding crystalline phases is mainly determined by three factors: mechanical, thermodynamic, and concentration-related.