In this paper, we have developed TiZrCuPd quaternary bulk glassy alloys which seem to be favorable for future application as biomaterials because of the absence of toxic elements such as Ni, Al and Be. A series of (TiZr) 50 (CuPd) 50 bulk glassy alloys exhibit high glass-forming ability (with critical diameters of 6 and 7 mm) and relatively large supercooled liquid region (ÁT x ) of over 50 K. This alloy system follows the three empirical rules for stabilization of supercooled liquid. The thermal stability of Ti 40 Zr 10 Cu 36 Pd 14 bulk glassy alloy was also examined in correlation with the origin for the high glass-forming ability.

In this research, Ti coating was conducted on Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glass (BMG) in order to increase the formation rate of hydroxyapatite layer. The formation behavior of bone-like hydroxyapatite on Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glasses (BMGs) was studied. The surface morphology of Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results revealed that the alkali pretreatment in 5 M NaOH solution at 60 C for 24 h had a beneficial effect on the formation of porous sodium titanate on Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG. A bone-like hydroxyapatite layer was able to form on the alkali-treated Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG after a short-time immersion in simulated body fluid (SBF). On the contrary, hydroxyapatite formation was not observed on the uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG after the same chemical treatments.

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Bulk glassy alloy rods with a diameter of 16 mm and a length of 40 to 45 mm were produced for Zr 65 Al 7:5 Ni 10 Cu 17:5 alloy by a tilt casting method. The alloy specimens taken from the different sites which are away by about 10 mm, 15 mm and 30 mm from the bottom surface of the cast rod consist of a glassy phase and their thermal stability, mechanical properties and fracture mode are almost independent of the specimen sites. The glass transition temperature, temperature interval of supercooled liquid region before crystallization and heat of crystallization are about 643 K, 102 K and 55 J/g, respectively, for the specimens taken from the three different sites. Besides, Young's modulus, yield strength, fracture strength, yield strain and plastic strain of the specimens are about 87 GPa, 1540 MPa, 1580 MPa, 0.018 and 0.005, respectively. The fracture mode consisting of shear plastic deformation along the maximum shear stress plane, followed by an instantaneous final rupture is also independent of the specimen sites. These data indicate that the cast glassy alloy rod with a diameter of 16 mm has nearly the same characteristics, though the cooling rate is significantly dependent on sample sites. The knowledge of producing the Zr-based bulk glassy alloy rod with nearly the same characteristics in the large diameter range up to 16 mm is encouraging for future applications of bulk glassy alloys as a new type of engineering material.

In this study, the microstructure and electrochemical properties of PVD TiN and (Ti, Al) N coatings on Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glass were investigated. The microstructure of TiN or (Ti, Al) N coatings, the BMG substrate and the interface was investigated by highresolution transmission electron microscopy. The electrochemical behavior of PVD coatings on the Ti-based BMG was studied by measuring potentiodynamic polarization curves in Hanks' solution. HREM observation revealed that the sputtering TiN ((Ti, Al) N) coating consisted of cubic TiN ((Ti, Al) N) phase with a lattice parameter of 0.426 (0.422) nm in nanoscale. The polarization curves showed that the open circuit potential shifted to a more positive potential and the passive current density decreased due to the protective TiN or (Ti, Al) N coating.

The elastic energy storing capability of bulk metallic glasses was evaluated by employing depth-sensing nanoindentation. The elastic energy densities of four glassy alloys, determined by nanoindentation measurements, are fairly close to their theoretical values estimated from elastic modulus and theoretical strength. This study provides an accurate and quick method to measure the elastic properties of bulk metallic glasses.

In this study, a bone-like apatite layer was formed on a Ni-free Ti-based metallic glass. A two-step treatment method, i.e., hydrothermalelectrochemical treatment followed by pre-calcification treatment, was developed to prepare a bioactive surface on the Ti-based metallic glass. The results reveal that the combination of electrochemical-hydrothermal and pre-calcification treatments can accelerate nucleation and improve growth rate of apatite on Ti-based metallic glass in simulated body fluid (Hanks' solution). The reasons why the two-step treatment accelerates the nucleation and growth of apatite were also discussed.

Bulk glassy alloy rods of diameters 18 and 20 mm were formed during the tiltcasting of Zr 60 Al 10 Ni 10 Cu 20 . A further increase in the rod diameter to 22 mm resulted in the formation of a mixed structure with approximately 60 vol% glassy phase and 40 vol% crystalline phase, which comprised the central region of the transverse cross-section of the alloy rod. The glass transition temperature (T g ), onset temperature of crystallization (T x ), and liquidus temperature (T l ) were measured to be 666 K, 768 K, and 1153 K, respectively, and the resultant ÁT x ð¼ T x À T g Þ, T g =T l , and ð¼ T x =ðT g þ T l ÞÞ values were 102 K, 0.578, and 0.422, respectively. The high glass-forming ability of supercooled liquids is attributed to the high resistance of the liquids against crystallization due to the large ÁT x and high T g =T l and values. For the alloy rod of diameter 20 mm, the Young's modulus, yield strength, elastic strain, and plastic strain under a uniaxial compressive load are 80 GPa, 1820 MPa, 0.022, and 0.060, respectively; the plastic strain of the rod with diameter 20 mm is greater than that (0.04) of the glassy alloy rod of diameter 2 mm, although there exist no appreciable differences between their strength levels and fracture behaviors. The success of formation of the large-sized Zr-based bulk glassy alloy rod, which exhibits large plastic strains in conjunction with high strength levels, is promising with regard to further extension of the applications of such highly functional materials.