Mossbauer study on crystallization behavior of glassy Fe58Co7Ni7ZrxB28-x (3 <= x <= 18) alloys with variable supercooled-liquid regions

Crystallization behavior of glassy Fe58Co7Ni7ZrxB28-x, (3 less than or equa l to x less than or equal to 18) alloys was examined by means of X-ray diff raction and Fe-57 Mossbauer spectroscopy in order to clarify the reason for the thermal stability against crystallization, where the thermal stability correlates strongly to the width of the supercooled-liquid region. Various crystalline phases appear in the specimens quenched from and annealed at t emperatures 50 K higher than the crystallization temperatures. Crystalline Fe3B and Fe2B phases characteristic of the B-rich alloys appear along with Fe,Zr and unidentified Fe-Zr-B phases characteristic of the Zr-rich alloys in the quenched Fe58Co7Ni7Zr8B20 specimen that originally has the widest su percooled-liquid region of 66 K. The competitive frustration in the forming ability of these compositional short-range order is one of the reasons for thermal stability against crystallization. Both the quenched and annealed Fe58Co7Ni7Zr3B25 specimens do not contain any phase with the Zr constituent . while the glassy Fe58Co7Ni7Zr3B25 alloy has the supercooled-liquid region of 34 K. This fact implies that the Zr impurities in Fe3B- and/or Fe2B-typ e compositional short-range order also play an important role in the therma l stability of these glassy alloys.