Preparation of amorphous Ni-Pd-P particles by melt ejection into stirred water and their hardness and thermal stability
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I.
INTRODUCTION
AMORPHOUSalloy
powders have been produced by several techniques such as gas-water atomization, ~ ultrasonic gas atomization, 2 spark erosion, 3'4 roller atomization, 5 melt ejection into rotating water, 6'7 centrifugal atomization, 8 and water atomization. 9 The techniques except roller atomization can produce spherical amorphous powders, but the maximum diameter is commonly smaller than several hundreds /zm, and no established melt-quenching technique to produce spherical powders with a larger size and good sphericity has been reported. If amorphous spherical powders with a diameter above 0.5 mm exhibiting high hardness and good corrosion resistance are produced by melt quenching, the powders can be expected to have a number of practical applications, such as the ball in a ball-point pen and the soldering ball for connection at which a high degree of dimensional accuracy is required. The present authors have investigated the technique of preparing amorphous spherical particles with a diameter above 0.5 mm and an appropriate alloy composition with high glass- and powderforming abilities. Most recently, it has been found that the melt-quenching method of ejecting Ni-rich Ni-Pd-P molten alloy into stirred cold water containing 1 vol pct surfactive agent is capable of producing amorphous spherical particles with diameters as large as about 1.4 mm. The aim of this paper is to present the technique, ejecting condition, and alloy composition, for producing amorphous Ni-Pd-P spherical particles with a diameter above 0.5 mm. The shape, hardness, structural relaxation, and crystallization
A. INOUE,AssociateProfessor,H. M. KIMURA,ResearchAssociate, and T. MASUMOTO, Professor, are with The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai 980, Japan. T. EKIMOTOand Y. MASUMOTO, Members of Research Staff, and N. MIYAKE,ExecutiveDirector, are with Sailor FountainpenCo. Ltd., Tokyo 110,Japan. ManuscriptsubmittedJune 9, 1986. METALLURGICALTRANSACTIONSA
temperature of the amorphous spherical particles are also described.
II.
EXPERIMENTAL PROCEDURES
Alloys with the composition ( N i l - x P d x ) l O o - y P y ( x = 0 0.4, y = 14 - 24 at. pct) and (Ni0.aPdo.2)8oP20-xB~ (x = 0 - 10 at. pct) were used in the present work. The alloy ingots were prepared by arc melting the mixture of pure metals of Ni (99.97 wt pct) and Pd (99.99 wt pct), pre-alloyed Ni-13.94 wt pct P and boron (99.8 wt pct). The compositions of the alloys are close to the nominal values since the losses during arc melting were negligible. Figure 1 shows a schematic illustration of the experimental apparatus used for the preparation of spherical particles. Ni-Pd-P ingots were placed within a quartz nozzle, remelted, and then ejected through an orifice of quartz nozzle into an agitated water with 1 vol pct surfactive agent (polyoxyethylene sorbitan monolaurate). The depth and outer diameter of the stirred water layer are about 80 mm and 90 mm, respectively, and the water temperature was 273 K. The revolving speed of th
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