H.J. Yang

Tensile softening of metallic-glass-matrix composites in the supercooled liquid region

A Ti-based metallic-glass-matrix composite exhibits tensile softening (necking) in the supercooled liquid region, accompanied by a large tensile ductility and a fragmentation of dendrites. Subjected to high temperatures, concurrent crystallization does not occur, suggesting a good thermal stability of the glass matrix. The presence of high-volume-fractioned dendrites lowers the rheology of the viscous glass matrix at high temperatures, which results in an absence of super elongation as monolithic bulk metallic glasses (BMGs). A tensile strength of 970 MPa is higher than those of most BMGs under varying strain rates, ascribing to the retardation of softening by the dendrites.

Corrosion Behavior of Ti-Based In Situ Dendrite-Reinforced Metallic Glass Matrix Composites in Various Solutions

The electrochemical corrosion behaviors of Ti40Zr24V12Cu5Be19in situ dendrite-reinforced metallic glass matrix composites (MGMCs) were investigated by potentiodynamic polarization experiments and electrochemical impedance spectroscopy in acidic, salty, and alkaline solutions. Ti40Zr24V12Cu5Be19in situ dendrite-reinforced MGMCs have an impressive corrosion resistance in strong acidic environment, while their performance was not so great in strong alkaline environment. Further immersion test in same solutions revealed similar chemical corrosion behaviors. XRD and SEM examinations were conducted to check the structure and surface modification of the material during the corrosion process. EDS test indicated that the amorphous matrices, which show excellent corrosion resistance, have a considerable composition variation from its crystalline dendrites counterpart.

Dendritic and spherical crystal reinforced metallic glass matrix composites

Zr-based bulk metallic glass matrix composites (BMGMCs) with a composition of Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4-Be10.0 (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.

In-situ Tension of Dendrite-Reinforced Zr-based Metallic-Glass-Matrix Composites

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.