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

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Abstract
Bulk nanocrystalline alloys with good ductility and high tensile strength (σf) 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 Zr2(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 Zr60Al10Cu30 amorphous alloy occurs by the simultaneous precipitation of Zr2Al and Zr2Cu 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 (Vf) range of the compound phase below 20 to 40%. The σf, Young’s modulus (E) and fracture elongation (ε) increase from 1760 MPa, 81.5 GPa and 2.10%, respectively, at Vf=0% to 1880 MPa, 89.5 GPa and 2.17%, respectively, at Vf=40% for the Zr60Al10Cu20Pd10 alloy and from 1750 MPa, 81.1 GPa and 2.21%, respectively, at Vf=0% to 1850 MPa, 85.6 GPa and 2.28%, respectively, at Vf=28% for the Zr60Al10Cu15Pd10Fe5 alloy. The formation of the bulk nanostructure alloys with high σf 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.