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 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 (V_f) range of the compound phase below 20 to 40%. The σ_f, Young’s modulus (E) and fracture elongation (ε) 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 Zr₆₀Al₁₀Cu₂₀Pd₁₀ 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 Zr₆₀Al₁₀Cu₁₅Pd₁₀Fe₅ 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.