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

Mechanical Properties and Thermal Stability of (Fe, Co, Ni)-Mo-C Quaternary Amorphous Alloys

This paper presents the results on the effect of alloy composition on the amorphous phase formation, crystallization temperature (Tx), hardness (Hv) and thermal embrittlement of (X, Y)_Mo_8C_ and (X, Y)_Mo_C_ (X, Y=Fe, Co and Ni) quaternary alloy systems. Continuous amorphous ribbons possessing good ductility were obtained in the limited ragne of 0-46 at. %Co for (Fe, Co)_Mo_8C_, 0-31 at. %Ni for (Fe, Ni)_Mo_8C_ and in the entire composition ranges of (Fe, Co)_- and (Co, Ni)_Mo_C_ Hardness decreased by the replacement of Fe with Co or Ni, and of Co with Ni, exhibiting a minimum value at about 0.7 Co/Fe+Co, 0.6 Ni/Fe+Ni and 0.7 Ni/Co+Ni. Further replacement resulted in an increase of the hardness. Crystallization temperature decreased by the replacement of Fe with Co or Ni over entire composition ranges and in the Co-Ni system it was almost constant. The embrittlement tendency increased by the replacement of Co or Ni with Fe and by mixing Co and Ni

Fatigue Strength of Amorphous Alloy Wires

Amorphous alloy wires in iron-, cobalt- and nickel-based alloy systems have recently attracted strong attention as a new type of engineering materials because of high mechanical strength, good ductility, good corrosive resistance and unique magnetic properties as well as fine geometry with circular cross section. This review aims to present the fundamental characteristics of fatigue strength of iron-, cobalt- and nickel-based amorphous wires by focussing on the following points; (1) the difference in fatigue strength among iron-, cobalt- and nickel-based amorphous wires, (2) the difference in fatigue strength between repetitive bending and tensile loads, (3) the mechanism of the initiation and propagation of fatigue crack, and (4) the influences of stress ratio, testing temperature, cold drawing, structural relaxation and environment on the fatigue strength and fracture morphology. Additionally, the advantage and disadvantage to use the amorphous wire as a reinforcing material for rubber tire have briefly been discussed based on the fundamental characteristics of fatigue strength

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