Journal of Powder Materials

Introduction to the Hot Isostatic Pressing and its Application: J Korean Powder Metall Inst. 1996;3(1):1-12.

Magnetic Properties of Permalloy(PB, PC) Strips Fabricated by Powder Rolling Process: J Korean Powder Metall Inst. 1996;3(1):13-24.

Abstract PDF: Two grades of Permalloy strips, Fe-45Ni(PB) and Fe-78Ni-4Mo-5Cu(PC) were fabricated by powder rolling process from elemental powder mixtures. The roll compacted green strips were sintered, homogenized, cold rolled with or without an intermediate annealing and finally heat treated to measure magnetic properties. For a given thickness reduction, rolling with an intermediate annealing was found more effective to achieve a full densification with no visible micropores and also to obtain better magnetic properties. Increasing the final rolling reduction also produced a marked improvement of the magnetic properties whereas the cooling rate during the final heat treatment has little effect in both grades. Addition of a small amount, 0.4% Mn slightly degraded the properties. As an overall, The PM strips produced via powder rolling yielded the similar soft magnetic properties to the corresponding commercial grades produced via wrought processing.

Modelling for the Flying and Cooling Behaviors of the Centrifugally Atomized Particles: J Korean Powder Metall Inst. 1996;3(1):25-32.

Abstract PDF: Flying and solidification behaviors of the particles manufactured by centrifugal atomization were investigated. Both models were solved by the explicit FDM. Flying calculation supported the experimental results that the finer particles flied shorter than coarser particles and that particles flied shorter for lower rotation velocity than for higher velocity. Cooling curve and dendrite arm spacing were predicted by use of heat transfer analysis.

On the Properties of Nanostructured Cu-Pb Alloys Prepared by Mechanical Alloying: J Korean Powder Metall Inst. 1996;3(1):33-41.

Abstract PDF: Nanostructured Cu-Pb powders were synthesized by mechanical alloying process. The variation of powder characteristics with mechanical alloying time was investigated by x-ray diffraction, differential scanning calorimetry, SEM and TEM. An electrical resistivity of the hot pressed specimens was also measured by using the nanovoltmeter. It was shown that mechanical alloying for 12 hours leads to a homogenization and a grain refinement to the nanometer scale under 20 nm. The mechanically alloyed Cu-Pb alloys represented the enhanced solid solubility of 10wt% Pb in the Cu matrix. The monotectic temperature of nanostructured Cu-Pb alloy decreased from equilibrium state of 955°C to 855°C due to reduced grain size effect. The analysis of electrical resistivity showed that the hot pressed MA Cu-5wt% Pb compact existed as a solid solution.

Alloying Behavior of Nb-25 at%Al Powder Mixtures by Mechanical Alloying: J Korean Powder Metall Inst. 1996;3(1):42-48.

Abstract PDF: To investigate the phase transformation behaviors of mechanically alloyed Nb-25 at%Al powders, the mixed Nb-25 at%Al powders were mechanically alloyed in SPEX 8000 Mixer/Mill. Mechanical alloying(MA) time was varied between 0.5 hour and 72 hours. The phase formation behaviors of these mechanically alloyed powders were examined using X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and differential thermal analysis(DTA). Appreciable amorphization started from 6 hours of MA. The powders mechanically alloyed for 10 hours were in almost amorphous phase. DTA results showed that the powders mechanically alloyed for 12 hours had a strong exothermic peak about600°C, whereas the powders mechanically alloyed for 6 hours had two exothermic peaks. The first peak was found to be due to the stress relief effect and the second one due to the formation ofNb_3Al,Nb_2Al and Nb_2Cphases by crystallization.

Effect of H_2/N_2 Sintering Atmosphere on the Carbon Content and Mechanical Properties in the Metal Injection Molding of Fe-Ni Mixed Powder: J Korean Powder Metall Inst. 1996;3(1):49-56.

Abstract PDF: The effect ofH_2/N_2gas sintering atmosphere on the carbon content and mechanical properties during the metal injection molding process of carbonyl iron-nickel powder was studied. The carbon content of the specimen after debinding in the pureN_2atmosphere appeared 0.78 wt%. After showing the maximum value of 1.48 wt.% in the debinding atmosphere of 10%H_2/N_2gas mixture, the carbon content of the debinded specimen decreased gradually with increasing theH_2content in theH_2/N_2gas mixture. The carbon contents of the sintered specimen were 0.46~0.63wt% in Na gas atmosphere, while they appeared extremely low above 40%H_2/N_2gas atmosphere. The relative sintered density increased abruptly from 88~90% to 93~96% with the addition of Ni, while the density nearly unchanged above 2% Ni addition. The sintered density increased with increasing the fraction ofH_2 in H_2/N_2gas mixture. Tensile strength and hardness increased, and elongation decreased with increasing carbon and Ni content. In spite of high carbon content of 0.63 wt%, the superior elongation value of 10% was shown.

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