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

摘要

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_2Al and Zr_2Cu 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.