Influence of the formation of intermetallics on the electrochemical properties of an Al₈₇Y₅Ni₈ amorphous alloy

Chem.Met.Alloys 1 (2008) 149-153

L. BEDNARSKA, T. MIKA, B. KOTUR, M. KOVBUZ, S. MUDRY

The influence of the formation of intermetallic compounds on the electrochemical properties of an Al₈₇Y₅Ni₈ amorphous metallic alloy (AMA) was investigated by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and high-resolution electron microscopy (HREM). It is shown that the crystallization process taking place upon annealing can be subdivided into three stages corresponding to DSC maxima at 505, 602 and 632 K, respectively. The first and the second stage of crystallization were attributed to the formation of an fcc-Al(Y) solid solution in the amorphous matrix. During the third stage of crystallization precipitation of the fcc-Al(Y) solid solution and of the ternary compound Al₁₉Y₃Ni₅ with orthorhombic Al₁₉Gd₃Ni₅-type structure was observed. An increase of the size of the precipitated phases reduces the corrosion rate coefficient b of the AMA.

HREM image of the Al₈₇Y₅Ni₈ sample heated up to 532 K with a heating rate of 20 K·min^-1.

Keywords

Amorphous metallic alloy / Crystallization process / Corrosion resistance