Zr-based bulk metallic glass matrix composites (BMGMCs) with a composition of Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be 10.0 (at%) were fabricated by an innovative process, i.e., semisolid processing plus Bridgman solidification. Different morphologies, distributions, and volume fractions of the crystalline phases can be achieved by tailoring the withdrawal velocity. The largest fracture strain of Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0(at%) composites with the withdrawal velocity of 1.0 mm/s was found to be 16.7%. The mechanism of plasticity improvement is mainly attributed to the interpenetrated structure of the crystalline phase, which greatly confines the rapid propagation of shear bands.
The evolution of shear bands in the glassy matrix composites was observed and analyzed during in-situ tension.Based on the simple calculation,the temperature rise within the shear bands is sufficient to cause the formation of viscous shearing layer,resulting in the early failure.Zr-based metallic-glass-matrix composites(labeled as DH1 and DH2) exhibit improved tensile ductility rather than brittle failure,since the existence of secondary ductile dendrites promotes the impedance of prompt propagation of shear bands,evidenced by the multiplication of shear bands.
In-situ dendrite-reinforced metallic glass matrix(MGM) composites with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0were prepared with a vacuum arc melter by the copper mold suction casting.Effect of different normal loads and sliding velocities on the tribological properties of MGM composites was studied. The results showed that the friction coefficient and wear rate of composites initially descended with increasing the normal load and reached a minimum of 0.339 and 1.826 10 4mm3/(N m) at 10 N,respectively, then ascended. Similarly, the friction coefficient and wear rate of composites initially decreased with the increase in the sliding velocity and reached a minimum of 0.330 and 2.389 10 4mm3/(N m) at0.4 m/s and 0.3 m/s, respectively, then raised. The wear mechanism of composites was mainly adhesive wear accompanied by abrasive wear at lower normal load and sliding velocity. However, the wear mechanism of composites was abrasive wear and adhesive wear as well as delamination at higher normal load and sliding velocity due to the nucleation and propagation of surface and subsurface cracks during the wear process. The flake-like and particle-like wear debris was the dominant shapes of debris observed.
