Nanocrystalline Zr-based bulk glassy alloys with high flexural strength

摘要

High flexural strength exceeding 4000 MPa combined with sufficient deflection was found to be obtained in a cast bulk glassy Zr{sub}55Al{sub}10Ni{sub}5Cu{sub}29Nb{sub}1 alloy consisting of crystalline regions with a size of 2 to 6 nm embedded in a glassy matrix. The phase with the fine mixed structure was named as a nanocrystalline glassy phase and produced by the combination of the following two effects; (1) metallurgical effect by the addition of Nb which enables us to form a supercooled liquid including homogeneous crystalline clusters resulting from the positive heat of mixing for Nb against Zr, and (2) the squeezing casting effect which enables us to form a bulk amorphous alloy keeping the specialized structural feature in the supercooled liquid. The nanocrystalline glassy structure was characterized to lie in a transient stage from the glassy to nanocrystalline phases and the structural feature was identified by high-resolution transmission electron microscopy.