Effect of high pressure on the crystallization of an amorphous Fe₈₃ B₁₇ alloy

Abstract

Amorphous Fe-17 at %B alloy prepared by a splat-quenching technique was annealed at temperatures ranging from 250 to 500° C for different periods. A time-temperature transformation diagram has been constructed from X-ray diffraction examination of annealed samples. On annealing the alloy at a pressure of 50 kbar, an appreciable retardation of crystallization was observed. The crystalline phase precipitated first from the amorphous matrix at 1 bar. This was α-Fe containing a small amount of boron, but at 50 kbar this was a mixture of α-Fe(B) and intermetallic phase Fe₃B. Under the increased pressure of 100 kbar the mode of the crystallization was further changed and Fe₃B became the first precipitating phase. Preferential formation of Fe₃B under pressure can be explained assuming a modified dense-random packing model for the amorphous structure.