Preparation and Mechanical Properties of Zr-based Bulk Nanocrystalline Alloys Containing Compound and Amorphous Phases

Abstract

Bulk nanocrystalline alloys with good ductility and high tensile strength (σ 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 nanoscale Zr 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 60 Al 10 Cu 30 amorphous alloy occurs by the simultaneous precipitation of Zr 2 Al and Zr 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 in diameter keep good ductility in the volume fraction (V f ) range of the compound phase below 20 to 40%. The σ f , Young's modulus (E) and fracture elongation (e) increase from 1760 MPa, 81.5 GPa and 2.10%, respectively, at V f =0% to 1880 MPa, 89.5 GPa and 2.17%, respectively, at V f =40% for the Zr 60 Al 10 Cu 20 Pd 10 alloy and from 1750 MPa, 81. 1 GPa and 2.21%, respectively, at V f =0% to 1850 MPa, 85.6 GPa and 2.28%, respectively, at V f =28% for the Zr 60 Al 10 Cu 15 Pd 10 Fe 5 alloy. The formation of the bulk nanostructure alloys with high σ f and good ductility in coexistent with the compound is presumably because the remaining amorphous phase can contain a number of free volumes 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.