High-strength bulk nanocrystalline alloys in a Zr-based system containing compound and glassy phases

Polycrystalline alloys with tensile strength (sigma(f)) in Zr-Al-Cu-Pd and Zr-Al-Cu-Pd-Fe systems were formed by partial crystallization of cast glassy alloys. The alloys consist of nanometer scale Zr(2)(Cu,Pd) surrounded by a glassy phase. The particle size and interparticle spacing of the compound are less than 10 and 2 nm, respectively. The crystallization of a ternary Zr(60)Al(10)Cu(30) amorphous alloy occurs by the simultaneous precipitation of Zr(2)Al and Zr(2)Cu with particle size of 200 nm and hence the addition of Pd is essential for formation of the nanostructure (NS). The NS cylindrical alloys of 2-3 mm in diameter keep good ductility in the volume fraction (V(f)) range of the compound below 40%. The sigma(f) and Young's modulus (E) increase from 1760 MPa and 81.5 GPa, respectively, at V(f) = 0% to 1880 MPa and 89.5 GPa respectively, at V(f) = 40% for the Zr(60)Al(10)Cu(20)Pd(10) alloy. The formation of the NS alloys with high sigma(f) in coexistence with the compound is presumably because the remaining glassy phase contains free volumes by quenching from the supercooled liquid. The synthesis of the high-strength bulk NS alloys is important for future development of new high-strength materials. (C) 1999 Elsevier Science B.V. All rights reserved.