Mechanical Characteristics of Amorphous Metals

This paper reviews new informations obtained from the latest experiments concerned with the mechanical properties of amorphous metals. The selected subjects are of static and dynamic properties, plastic deformation and toughness, and several important effects on mechanical behaviors such as compositional, structural and environmental effects. Amorphous metals are a new type material having consistently very high strengths together with a distinguished toughness and also they are classified as an elastic-perfectly plastic solid. In amorphous transition metal-metalloid alloys, the alloy system containing silicon and boron has high values of strengths and hardness, and a wide region of concentrations for becoming amorphous. An appreciable loss of ductility in some amorphous ferroalloys takes place by aging at temperatures much lower than the crystallization temperature or by hydrogen embrittlement under a corrosive condition

Relaxation, Crystallization and Consolidation of an Amorphous Pd_<48>Ni_<32>P_<20> Alloy Powder

The influence of applied pressure on the structure relaxation, glass transition, crystallization and consolidation for an amorphous phase was examined by using a typical glassy Pd_Ni_P_ alloy in a spherical powder or a ribbon form. The Pd-Ni-P alloy was chosen because of the existence of a wide supercooled liquid region in the temperature range below crystallization temperature (T_x). The relaxation and crystallization are significantly suppressed by the application of compressive load, presumably because of the increase in viscosity and the decrease in diffusivity. As a result, the pressing at a high temperature of 0.97T_x is required to produce an amorphous bulk with high relative density. Furthermore, an intermediate annealing between pressings was found to be effective for the reduction of the enhanced viscosity. The multistage pressing treatment consisting of pressing and annealing enabled to produce a highly dense amorphous bulk even at a relatively low temperature near T_g

SOFT MAGNETIC PROPERTIES OF AMORPHOUS Fe-Co-Ni BASE ALLOYS WITH Si AND B

Amorphous alloys of Fe-Co-Ni-Si-B system with a wide composition have been produced by a conventional rapid quenching method, and their soft magnetic properties have been examined. The Fe-rich alloys having a high saturation magnetization (～ 1.6×10^4 G) exhibit a rectangular-type B-H hysteresis loop with low coercive force of about 0.01 Oe when the alloys are subjected by a magnetic field cooling. On the other hand, the Co-rich non-magnetostrictive alloys exhibit a high effective permeability ( 50 - 100×10^3 ) at the initial magnetization and audio frequency range. The detailed compositions and heattreatments in obtaining the best soft magnetic properties, and the characteristics which may be interest in engineering applications will be reviewed

Determination of Condition for Electrolytic Extractions of Nitrides in Steel by Means of Potentiostat

The polarizing characteristics of synthesized nitrides, Fe_3N, Fe_4N, Mn_3N_2 Mo_2N, MoN, Cr_2N CrN, VN, Si_3N_4 AlN, TiN, ZrN and NbN, were studied by means of potentiostat in order to determine the condition for the electrolytic extractions of nitrides from iron and steel. From the results of polarization curves and natural electrode potentials of iron and nitrides, some useful informations were obtained as to the electrolyte and the electrolytic potential for the electrolytic extractions of nitrides contained in iron and steel ; that is, if a suitable electrolytic potential is applied, both acidic and neutral solutions can be used as an electrolyte for the extractions except nitrides of Al, Fe and Mn. For the Fe-nitride, only neutral electrolyte is useful, while for the nitrides of Al and Mn, there seems to be no favorable electrolyte

Hydrogen-Induced Amorphization in Intermetallic Compounds

This article briefly reviews our recent studies on the hydrogen-induced amorphization (HIA), i.e., the transformation from the crystalline to the amorphous state by hydrogen absorption, of the intermetallic compounds. The experimental evidence of amorphization, the amorphizing alloy systems, the progress and the mechanism of HIA, and the influence of HIA on the magnetic properties of the intermetallic compounds are described

Indirect Optical Absorption of Single Crystalline beta-FeSi2

We investigated optical absorption spectra near the fundamental absorption edge of beta-FeSi2 single crystals by transmission measurements. The phonon structure corresponding to the emission and absorption component was clearly observed in the low-temperature absorption spectra. Assuming exciton state in the indirect allowed transition, we determined a phonon energy of 0.031 +- 0.004 eV. A value of 0.814 eV was obtained for the exciton transition energy at 4K.Comment: 10 pages with 3 figure

Amorphous Magnetic Alloys

The alloy systems for amorphous magnetic alloys are devided into the metal-metalloid type and the metal-metal type. The former alloys consist of ferromagnetic transition metals (TM : Fe, Co and Ni) and metalloid elements (B, C, Si, P and Ge). On the other hand, the amorphous alloys belonging to the latter type are limited to several alloy systems of TM-Zr and TM-Hf. In this paper, the subjects covered include the composition dependence of the magnetization, Curie temperature, magnetostriction, coercive force and permeability for two types of amorphous magnetic alloys. Finally, the examples of the alloy design for some applications and their magnetic characteristics are briefly introduced

Effects of Alloying Elements on the Corrosion Behavior of Amorphous Cobalt-Base Alloys

Corrosion characteristics of amorphous cobalt-base alloys in 1N HCl have been investigated by immersion and electrochemical techniques. The corrosion resistance of amorphous Co-P-B alloy is intermediate between those of amorphous Fe-P-B and Ni-P-B alloys. The alloying with chromium, molybdenum, tungsten, nickel and copper is effective in improving the corrosion resistance. In particular, the addition of chromium and the combind addition of chromium with molybdenum lead to spontaneous passivation. The corrosion resistance of chromium-bearing alloy is improved by alloying with various metalloids but is lowered by an increase in boron and silicon. All alloys which passivate do not suffer pitting corrosion even by anodic polarization in 1N HCl

Elinvar Characteristics of Amorphous Alloys and Their Applications

The elastic properties and the Elinvar characteristics of various kinds of amorphous alloys are introduced. The Elinvar characteristics of Fe-base ferromagnetic amorphous alloys arises from their large ΔE effect. The elastic properties are sensitively affected by the internal stress, and the Elinvar characteristics is also obtained even in nonferromagnetic amorphous alloys such as Pd-Si and Ni-Si-B alloy systems by annealing or cold-rolling. A large stiffening is observed in Fe-base amorphous alloys in the saturated magnetic field, being different from the pole effect. The applications of the amorphous Elinvar alloys to mechanical vibrators and delay lines are described as examples, and then the merits and problems for their applications are pointed out from the practical point of view

Study on the Production of Flaky Amorphous Alloy Powders by Impact Flattening of Atomized Liquid Droplets on a Rapidly Rotating Wheel

A two-stage quenching technique consisting of impact flattening of atomized supercooled liquid droplets caused the production of flaky amorphous powders with a thickness of 1 to 3μm and an aspect ratio of 20 to 300 in Co-, Fe- and Al-based systems. The flaky powders consist of an amorphous phase over the entire particle size range even in the alloy systems where no amorphous phase is formed in the particle size below 25μm by high-pressure gas atomization. The improvement of the production ratio of the amorphous powders is due to the following three factors; (1) the second-stage cooling of supercooled liquid droplets, (2) the reduction of powder thickness to 1 to 3μm, and (3) the high thermal conductive state between rotator and powder resulting from the high-energy collision. The flaky powders also have smooth surface and edge combined with a uniform thickness, leading to good luster, high reflection ratio against light, high corrosion resistance, high mechanical strength and anisotropic magnetic properties. Furthermore, the unique morphology causes a high laminating tendency in a resin. By utilizing these advantages, the flaky amorphous powders are expected to be used as magnetic filler and corrosion-resistant coating materials