The 3D morphological evolution of titanium foams as they undergo a two-step fabrication process is quantitatively characterized through x-ray micro- and nano-tomography. In the first process step, a Cu–Ti–Cr–Zr prealloy is immersed in liquid Mg, where Cu is alloyed with Mg while a skeleton of crystalline Ti–Cr–Zr is created. In the second step, the Mg–Cu phase is etched in acid, leaving a Ti–Cr–Zr foam with submicron struts. 3D images of these solidified Ti–Cr–Zr/Mg–Cu composites and leached Ti–Cr–Zr foams are acquired after 5, 10, and 30 min exposure to liquid Mg. As the Mg exposure time increases, the Ti–Cr–Zr ligaments grow in size. The tortuosity loosely follows the Bruggeman relation. The interfacial surface distribution of these Ti-foams is qualitatively similar to other nano-porous metal prepared by one-step dealloying. The characteristic length of the Mg–Cu phase and pores are also reported.

Zr65Al7.5Ni10Cu12.5Nb5 glass was found to exhibit a large plastic compressive strain of over 10% and the property was suggested to be due to deformation-induced nanocrystallization. A transmission electron microscopic observation, however, only revealed obscure ordered clusters with a size of ˜2 nm in the fracture surface of a deformed sample, instead of well-identified crystals as previously reported for the Zr–Al–Ni–Cu–Pd system. This phenomenon is suggested to correlate with the higher viscosity of supercooled liquid and the slower grain growth of icosahedral phase during primary crystallization in the Zr65Al7.5Ni10Cu12.5Nb5 compared to those in the Zr65Al7.5Ni10Cu12.5Pd5 alloy. The role of the deformation-induced nanoclusters on the enhanced compressive plasticity was discussed.

In this study, we investigated the effects of methyl-β-cyclodextrin (MBCD) on in vitro fertilization and the subsequent development of bovine oocytes. Bovine oocytes matured in serum-free medium were inseminated with frozen–thawed sperm pre-incubated in protein-free modified Brackett and Oliphant medium (BO) containing various concentrations of MBCD for various periods. MBCD decreased the frequency of live sperm, however enhanced the capacitation and acrosome reaction of the live sperm. Pre-incubation of sperm with 0.5, 1.0 and 1.5 mM MBCD for 2 and 4 h increased the frequency of normal fertilization. Embryos derived from oocytes fertilized with spermatozoa pre-incubated with MBCD developed normally to the blastocyst stage and term. There were individual differences and similar tendencies in four different sires in terms of the effects of MBCD upon fertilization. These results indicate that the pre-incubation of bovine sperm with MBCD affects viability and capacitation status of the sperm and promotes fertilization in vitro. Embryos derived from oocytes fertilized with sperm pre-incubated with MBCD developed normally to the blastocyst stage and term.

This article presents a comparative study of the deformation-induced structural changes observed within a glassy phase in two different Zr- and Ni-based alloys. Ductile Zr65Al7.5Ni10Pd17.5 bulk glassy alloy, which exhibits dynamic nanocrystallization forming a crystalline cubic phase within shear bands on plastic deformation, is presumed to contain pre-existing nuclei. On the contrary, no obvious dynamic nanocrystallization is observed within the shear bands in the glassy phase of the Ni50Pd30P20 bulk alloy, which, however, contains clear medium-range order zones on the order of 1 nm in size in an as-solidified state. This alloy exhibits nucleation and growth-transformation behavior on heating. At the same time, clear nucleation and growth of the cubic Ni-based phase are observed near the microcrack area in the deformed sample. High energy released at the time of the microcrack propagation caused nanocrystallization and blockage of the crack-tip propagation.

A Zr65Al7.5Ni10Cu17.5-xPdx (x=0-17.5 at. %) alloy system is found to exhibit a unique dependence of glass-forming ability (GFA) on casting atmosphere during mold-casting process. High-Pd containing alloys (x=7.5-17.5) showed a remarkable increase of critical size (dc) for glass formation, in contrast with the low-Pd containing alloys (x=0-5) in which no significant change in dc was observed, as the pressure of Ar atmosphere varied from vacuum to ambient. The origin of the phenomenon has been successively unveiled by correlating the cooling characteristic during casting process and phase transformation behavior during continuous cooling of the alloy system. The consequence in the structure and property control is investigated and discussed in detail.

A new type of Mg–Zn–Cu–Gd-based alloy strengthened by quasicrystal and Laves phase was developed. This alloy exhibits much better creep properties compared to AE42(Mg–4 wt% Al–2 wt% rare-earth) alloy, which is the benchmark creep-resistant magnesium die-casting alloy under the compressive creep condition of 180 °C and80 MPa. The new alloy also exhibits high room-temperature mechanical properties close to that of AZ91 alloy. The good mechanical properties are attributed to the special microstructure; the thermally stable icosahedral quasicrystals phase (i-phase) and Laves phase distributed along the grain boundary as a hard skeleton, and some fine β′1 precipitates distributed homogenously on the matrix. The dislocation morphology after the creep test was studied, and the strengthening mechanism was proposed.

The primary transformation reaction of the Zr65Al7.5Cu27.5 ternary glassy alloy with a low oxygen impurity of approximately 100 mass ppm was investigated. We have discovered the precipitation of the metastable icosahedral phase with a fine grain size of 50–100 nm in diameter accompanying with the formation of stable Zr2Cu phase at the annealing temperatures ranging from 715 to 730 K. The lattice spacing of Zr2Cu phase decreases at higher temperatures, which is attributed to the rearrangement of Zr and Cu in the decomposition of the icosahedral phase. It is suggested that the formation of the icosahedral phase in the primary stage originates from the existence of the quenched-in icosahedral local atomic configuration in the glassy state.

The structure of hypoeutectic, hypereutectic, and eutectic Ti–Fe alloys produced in the shape of arc-melted ingots was found to consist of the ordered Pm-3m TiFe and disordered BCC Im3m β–Ti solid solution phase. The dimensions of the ingots were about 25–40 mm in diameter and 10–15 mm in height, and their structure was studied by x-ray diffractometry and scanning electron microscopy. The rectangular parallelepiped-shaped samples 2.5 × 2.5 × 5 mm in size cut from the central part of the ingots exhibit a high strength of about 2000 MPa, except for Ti60Fe40, and a certain ductility. The relatively low density of Ti (4.5 Mg/m3) implies high strength/density ratio for the studied alloys. These alloys are characterized by the low cost of the alloying element Fe and, compared to most of the high-strength non-equilibrium materials, do not require additional injection mold casting or rapid solidification procedures.

The structure and mechanical properties of Mg–Zn–Al–Y base cast alloys containing an icosahedral quasicrystal phase (i-phase) as a main strengthening phase were investigated. Mg–8Zn–4Al–xY base bulk alloys containing the i-phase were prepared by casting into a copper mold at moderate cooling rates. The Y addition was effective for decreasing the size of the i-phase and the increasing the homogeneity of its dispersed state. The mechanical properties examined by compression tests at room temperature were much superior to those of a conventional AZ91 Mg alloy. The creep tests at elevated temperatures indicated a promising high temperature creep resistance of the quasicrystal-reinforced Mg–Zn–Al–Y cast alloy. The strengthening mechanism was also discussed.

Mechanical properties and fracture characteristics of Zr-based bulk metallic glass (BMG) composites containing carbon nanotube (CNT) addition were investigated in detail. The interfacial reaction between the added CNTs and the glass matrix causes the formation of some V-shape nicks on the residual CNTs. These nicks have significant effect on the mechanical properties and fracture modes of the BMG composites. The compressive fracture strength increases with increasing the volume fraction of CNT addition at first, and starts to decrease gradually when the volume fraction of CNT addition is more than 5.0%. The fracture modes of the BMG composites also change from typical shear flow deformation behavior to completely embrittling fracture gradually. The V-shape nicks originating from the interfacial reaction are responsible for the decrease of fracture strength and the variation of fracture modes.

The high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25–40 mm in diameter and 10–15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed.

Heat evolution of stress-induced structural disorder, ΔHs(ε), of a Zr55Al10Ni5Cu30 bulk metallic glass (BMG) during constant ram-velocity deformation at the glass transition region (Tg= 680 K) was deduced from in-situ measurements of temperature change of the deforming sample. At the transition from the linear to nonlinear viscoelasticity, the behavior of viscosity change with strain, η(ε), is qualitatively consistent with the enthalpy evolution of the structural disordering, ΔHs(ε), but not with the temperature change, ΔT(ε). It is concluded that the initial softening deformation is due to the stress-induced structural disordering. The change in the nonlinearity, -log ñ ≡ −logη/ηN, is found to be proportional to the ΔHs and the slope of ΔHs(–logñ) can be estimated to ∼ 400 J/mol, where ηN is the Newtonian viscosity. On the other hand, the temperature raise, ΔT(ε), is pronouncedly delayed as compared with the η(ε) and ΔHs (ε) at the transition, but is determined by the product of stress and plastic strain-rate, σ·εp, and is nearly proportional to it at the steady-state. The slope of ΔT(σ·εp) can be estimated to 5.2×10-2 K mol/W.

Rapidly solidified ribbons of B2-ordered Fe-40, 45 and 50mol%Al were produced by a conventional single-roll melt-spinning method. The lattice parameters of as-spun ribbons are fully restored by annealing at 723 K for 24 h. This suggests that large numbers of supersaturated thermal vacancies are removed by the heat treatment. After the heat treatment, it is found that clustering of the supersaturated vacancies leads to a large number of pores that have a few hundreds nm or less in diameter near the surfaces, thus creating nanoporous surfaces. DSC measurements show irreversible exothermic peaks due to vacancy clustering. Vacancy complexes such as dislocations and pores are also observed inside the ribbons by TEM. The volume fraction of the overall vacancy complexes shows Al concentration dependence, demonstrating that defect structure formed by clustering of the excess vacancies is controllable by changing Al concentration in rapidly solidified FeAl ribbons.

The transformation from Newtonian to non-Newtonian viscous flow at the glass transition of Pd- and Zr-based alloy glasses has been investigated in compressive tests under either a constant strain rate, or a constant load. The transition occurs at a critical stress being nearly independent of temperature. The mechanism of the transition thus has been attributed to the stress-induced structural relaxation. This paper describes the evidence of stress-induced disorder as indicated by the change in the viscosity with stress and the evolution of specific heat of the alloy glasses subjected to non-Newtonian steady-state viscous flow. Also presented in this paper is the in-situ observation of structural disorder, by direct measurements of the temperature change of sample, in particular the soften process during a constant load deformation. The heat of evolution is then calculated, and found to scale as the logarithm of the normalized viscosity during entire deformation. This result implies that the relationship between the structural disorder, as indicated by the enthalpy change and viscosity is the same in the transient state during deformation as well as in the steady-state flow process. This is conceptionally very important in that it enables us to introduce a fictive stress which indirectly represents the glass structure.

Cylindrical composite Zr55Al10Ni5Cu30 bulk glassy alloys containing up to 17.5 vol.% ZrC particles were prepared with using an in-situ reaction forming ZrC between graphite particles with diameters of ∼10 m and Zr metal in molten alloy during arc-melting followed by copper mold casting. Because the in-situ reaction suppresses an agglomeration and segregation among dispersoids in the glassy matrix, mechanical properties of the composite materials at room temperature, especially toughness and plastic elongation, were significantly improved from the Zr55Al10Ni5Cu30 single glassy phase. In order to demonstrate the influence of the dispersed ZrC particles on workability of the supercooled liquid of the alloy, viscous flow behaviors under constant strain-rates were investigated. Although the Newtonian viscosity becomes larger, the composite material has the same viscoelastic properties, i.e., “shear thinning”, and excellent workability as the single glassy phase in spite of the dispersed particles.