Synthesis and mechanical properties of bulk amorphous Zr-Al-Ni-Cu alloys containing ZrC particles

Bulk amorphous Zr55Al10Ni5Cu30 composites containing ZrC particles up to 17 vol% were formed in a cylindrical form with diameters of 1 to 3 mm by a copper mold casting process. The average particle size and interparticle spacing of the ZrC particles are 3 and 4 mu m, respectively, and neither distinct agglomeration nor segregation of the ZrC particles is seen on the transverse and longitudinal cross-sections. The glass transition temperature (T-g), crystallization temperature (T-x) and melting temperature (T-m) of the amorphous matrix remain unchanged in the volume fraction (V-f) range up to 17%. Neither appreciable second crystalline phase nor voids are seen even at the interface between the amorphous and ZrC phases, though the amorphous matrix has a relaxed disordered structure. The interface has a rugged morphology on a nanometer scale and does not have any faceted plane. The Young's modulus, compressive strength (sigma(f)) and Vickers hardness for the composite alloys increase almost linearly from 103 to 125 GPa and 1820 to 2170 MPa and 488 to 563, respectively, with increasing V-f from 0 to 17%. The plastic elongation (epsilon(p)) also increases from nearly zero % at 0 vol% to 0.5% at 10 vol%. The significant increase in epsilon(p) is presumably due to the increase in the amount of shear sliding before adiabatic final rupture resulting from the increase in sigma(f). The viscous flow of the supercooled liquid is also suppressed by the dispersion of the ZrC particles. The success in synthesizing the high-strength bulk composite alloys consisting of ZrC particles embedded m the amorphous matrix is important for future development of bulk amorphous alloys.