Journal of Materials Research
November 2005— Volume 20, Number 11

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Crystallization behavior and microhardness evolution in Al92-xNi8Lax amorphous alloys K.L. Sahoo National Metallurgical Laboratory, Jamshedpur 831007, India M. Wollgarten Department of Materials, Hahn-Meitner-Institut Berlin, D-14109 Berlin, Germany K.B. Kim Division of Physical Metallurgy, Darmstadt Technical University, D-64287 Darmstadt, Germany J. Banhart Department of Materials, Hahn-Meitner-Institut Berlin, D-14109 Berlin, Germany

The crystallization behavior of melt-spun amorphous Al_92-xNi₈La_x (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.

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