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Fracture toughness tests were carried out using different Zr composition in Zr-Cu-Al based bulk metallic glasses (BMGs) and heat-treated those just under the glass transition temperature (Tg) in order to examine the effects of Zr composition and heat-treatment on the fracture toughness (KQ; fracture toughness including the values under unsatisfying the plane strain condition). Zr50Cu40Al10, Zr55Cu35Al10 and Zr60Cu30Al10 BMGs fabricated by a tilt ark casting method were used. Heat-treatments were done for 90 minutes just under the Tgs of each BMG. Tests were conducted based on ASTM E399. Compact type specimen was used (thickness=2.3, 2.0 mm, thickness : width=1 : 4). Fatigue pre-crack was induced under ΔK less than 6 MPa•m1/2 by a servohydraulic fatigue machine and the fracture toughness test was done by using the same machine. The KQ dominantly increased with increasing the Zr composition. The KQ in heat-treated BMGs decreased in comparison with that in unheat-treated BMGs in all Zr composition. In the BMG of the high Zr composition, however, the decrease was small after heat-treatment, and the KQ showed enough high values. In heat-treated BMGs, the dispersion of KQs did not become small, but fatigue pre-cracks were induced more vertical against the loading axis and less bifurcation than those in unheat-treated BMGs.

Bulk metallic glass (BMG) exhibits remarkable properties such as high strength, good stiffness and good corrosion resistance. However, the wear resistance of amorphous metals is not excellent as expected their high strength. It is thought that large local shear bands easily change into cracks for debris formation. The effective obstruction of shear band formation might be applied to improve the wear resistance of BMG. In this study, we tried to suppress shear band deformation by fine crystalline phase dispersion formed by semi-conductor laser irradiation. The microstructures of irradiated Zr-based BMG specimens were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The fine dispersions of crystalline phases are observed in the amorphous matrix. The optimum condition for laser irradiation was discussed.

Bulk metallic glasses (BMGs) have many unique mechanical properties, e.g. extremely high strength and bending ductility. However, very limited data are reported on tensile ductility on BMGs. Recently there has been interest in strain rate dependence of fracture behavior in BMGs, such as fracture strength, plastic deformation and shear band formation. Meanwhile, we indicated that a hypoeutectic Zr-Cu-Al BMG shows longer and many shear bands and higher fracture toughness than a eutectic Zr-Cu-Al BMG. In this study, tensile test on a hypoeutectic Zr-Cu-Al BMG is performed under several different strain rates. Effect of strain rate on the mechanical properties such as tensile strength and Young's modulus are investigated. Also, it is ascertained whether the tensile plastic elongation in the hypoeutectic Zr-Cu-Al BMG occur or not. The hypoeutectic Zr-Cu-Al BMG is fabricated by an arc-tilt casting method. Chemical composition is Zr60Cu30Al10 at%. Tensile test is carried out under several strain rates. As a result, it was found that Young's modulus, tensile strength and elastic strain are about 90 GPa, 1700 MPa and 2%, respectively. Also the tensile specimen fractured with the shear plane inclined 52-55 degree for the loading axis. All these values were independent on the strain rate. Under any strain rate, the tensile plastic elongation did not occur and the multiple shear bands were not observed in the specimen surface.

The local ordering structure of amorphous Fe89Nd 7 B 4 and Feg9Zr 7 B 4 alloys has been determined by anomalous X-ray scattering (AXS) coupled with the conventional X-ray diffraction method using Mo K^ radiation.The atomic distance and its coordination number in the nearest neighbor region obtained by a least-squares variational method indicate that the local ordering structure of both amorphous alloys appears to be no closer to the crystalline precipitates than a random packing of the present alloy composition and then any specific different structural feature could not be suggested in these two as-quenched amorphous alloys.

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Soft-magnetic fibers (SMFs) play a crucial role in energy conversion, transmission, and storage within electronic devices. However, conventional SMFs have poor plasticity and are therefore difficult to withstand long-term tensile, torsional, and shear deformation. A high fraction of grain boundaries could improve plastic deformability of conventional SMFs, but deteriorates the coercivity. This severely limits their applications in flexible electronics and multifunctional components. Herein, we propose a strategy to overcome this dilemma, which is realized by coarsening the grains of a Fe34Co29Ni29Al3Ta3Si2 high entropy alloy (HEA) fiber containing ordered coherent nanoprecipitates with small lattice misfit via a simple one-step in-rotating-water spinning method. This allows to reduce domain wall pinning and improve dislocation mobility. The resultant micron-diameter soft-magnetic HEA fiber has a tensile strength of 674 MPa at 23% elongation, a low coercivity of 8.1 Oe, a moderate magnetization of 116 emu/g at 10 kOe and a high Curie temperature of 770 K. Fe34Co29Ni29Al3Ta3Si2 high entropy alloy fibers with low coercivity and large plasticity are prepared. The fibers have a tensile strength of 674 MPa at 23% elongation, a coercivity of 8.1 Oe and a high Curie temperature of 770 K.