Crystallization behavior and microhardness evolution in Al92-xNi8Lax amorphous alloys

Abstract

The crystallization behavior of melt-spun amorphous Al92-xNi8Lax (x = 4 to 6) alloys was investigated by means of differential scanning calorimetry, x-ray diffractometry, and transmission electron microscopy. Crystallization kinetics were analyzed by Kissinger and Johnson-Mehl-Avrami approaches. Microhardness of all the ribbons was examined at different temperatures and correlated with the corresponding structural evolution. The results show that the variation of La content from Al88Ni8La4 to Al86Ni8La6 has significant influence on the crystallization pathways from amorphous to stable crystalline phases and on the evolution of microhardness with temperature. The two stages of crystallization in Al88Ni8La4 and Al87Ni8La5 alloys correspond to formation of fcc-Al and Al11La3, Al3Ni, Al3La. In Al86Ni8La6, three stages of crystallization are observed which correspond to formation of a metastable phase, fcc-Al, Al11La3, Al3Ni, and Al11La3, Al3Ni, Al3La, and decomposition of a metastable phases to stable crystalline phases.