Preparation and mechanical properties of Zr-based bulk nanocrystalline alloys containing compound and amorphous phases

摘要

Bulk nanocrystalline alloys with good ductility and high tensile strength (σ{sub}f) in Zr-Al-Cu-Pd and Zr-Al-Cu-Pd-Fe systems were formed by partial crystallization of cast bulk amorphous alloys. The nanostructure alloys consist of nanoscaleZr{sub}2(Cu, Pd) compound surrounded by the remaining amorphous phase. The particle size and interparticle spacing of the compound are less than 10 and 2 nm, respectively. The crystallization of a ternary Zr{sub}60Al{sub}10Cu{sub}30 amorphous alloy occurs by the simultaneous precipitation of Zr{sub}2Al and Zr{sub}2 Cu phases with large particle size of about 500 nm and hence the addition of Pd is essential for formation of the nanostructure. The nanostructure alloys in the cast cylinder of 2 to 3 mm indiameter keep good ductility in the volume fraction (V{sub}f) range of the compound phase below 20 to 40%. The σ{sub}f, Young's modulus (E) and fracture elongation (ε) increase from 1760 MPa, 81.5 GPa and 2.10%, respectively, at V{sub}f=0% to 1880MPa, 89.5 GPa and 2.17%, respectively, at V{sub}f=40% for the Zr{sub}60Al{sub}10Cu{sub}20Pd{sub}10 alloy and from 1750MPa, 81.1GPa and 2.21%, respectively, at V{sub}f=0% to 1850MPa, 85.6GPa and 2.28%, respectively, at V{sub}f=28% for theZr{sub}60AI{sub}10Cu{sub}15Pd{sub}10Fe{sub}5 alloy. The formation of the bulk nanostructure alloys with high σ{sub}f and good ductility in coexistent with the compound is presumably because the remaining amorphous phase can contain a number of freevolumes by water quenching from the supercooled liquid region. The synthesis of the high-strength bulk amorphous alloys containing nanoscale compounds is important for future development of a new type of high-strength material.