COMPARISON OF THE CORROSION BEHAVIOR OF A BULK AMORPHOUS METAL, Zr41.2Ti13.8Cu12.5Ni10Be22.5, WITH ITS CRYSTALLIZED FORM

Since the discovery of the first metallic glass in 1960 (1), amorphous metals have been made in a variety of compositions. However, they have been largely fabricated as thin ribbons less than a millimeter in thickness because fast cooling rates (;10 K/sec) have been required to retain the metastable amorphous phase. Recently, however, a new class of amorphous metals has been developed which require cooling rates of only 1 K/sec (2); these alloys, such as Zr41.2Ti13.8Cu12.5Ni10Be22.5 (at%), can thus be processed in bulk form. Amorphous metals have generated much interest, both in basic research and for structural applications, because of their near-theoretical strength to stiffness ratios and extremely low damping characteristics (3). In addition, a number of amorphous metals exhibit excellent corrosion resistance (4–7), which has been explained in terms of their structural homogeneity. Since amorphous metals are in principle structurally and chemically homogeneous and thus lack any microstructure, such as grain boundaries, which could act as local electrochemically-active sites, many researchers attribute “good corrosion resistance” to the entire class of amorphous metals. It is this point, whether the amorphous condition itself confers improved corrosion resistance, that we examine in the present note.