Journal of Powder Materials

State of the Art Powder Forging in Automotive Parts: J Korean Powder Metall Inst. 1995;2(1):1-7.

Densification and Microstructural Design of Ceramics for Auto Parts: J Korean Powder Metall Inst. 1995;2(1):8-18.

Preform Design for Forging of a PIM Connecting Rod: J Korean Powder Metall Inst. 1995;2(1):19-28.

Abstract PDF: Powder forging is a combined technology of powder metallurgy and precision hot forging. Recently, the technology is developing rapidly because of its economic merits, especially in automotive part manufacturing. In the present study, the finite element technique was developed to predict density variation during P/M forging and the technique was applied to analysis of forging of a P/M connecting rod. Although deformation mode of the connecting rod was quite complex, several sections were selected and analyzed under an assumption of asymmetric or plane strain deformation. It was found that some modifications were necessary on the cross section of the beam portion. Therefore, the cross section was modified repeatedly until a satisfactory result of the analysis was obtained. On the other hand, no modifications were necessary in the ring and the pin portions. It is anticipated that the developed technique can be used to optimize preform design and manufacturing processes in P/M forging, which are highly critical to produce successful products in practice.

Calcined Condition and Characteristic of Cu-Ni-Zn Ferrite Powder Made by Thermal Decomposition of Organic Acid Salt: J Korean Powder Metall Inst. 1995;2(1):29-35.

Abstract PDF: In this study the calcined condition and characteristic of Cu-Ni-Zn ferrite powder were investigated. The Cu-Ni-Zn ferrite powder has been synthesized by the thermal decomposition of the organic acid salt. This process did not require a strict pH control and provided the uniform composition and fine powder with about 0.3 mutextrmm. The XRD diffraction pattern of this powder showed about 50% spinel phase. The optimum calcination was found to be done at 700°C for one hour. After the calcination, the amount of spinel increased to 90%. The distribution of the particle size showed bimodal peaks, one was about 0.5 mutextrmm and the other was about 20 mutextrmm. The large particles of 20 mutextrmm were the agglomeration of fine Particles. The mean Particle size of the powder was about 0.4 mutextrmm. The powder was compacted under 100 MPa pressure and sintered at 1100~ 1250°C for one hour in air. The density of ferrites specimen was a function of the sintering temperature. The higher the temperature, the denser the ferrite. The maximum relative density of the sintered ferrite was about 93% at 1250°C. The grain size of sintered specimen at 1200°C was 5 mutextrmm and homogeneous.

Mechanical Properties of Al-Ti Base Alloys Processed Via Rapid Solidification and Mechanical Alloying: J Korean Powder Metall Inst. 1995;2(1):36-43.

Abstract PDF: Rapidly solidified and mechanically alloyed Al-Ti base alloys were prepared by gas atomization and attritor milling separately. The gas atomized and the mechanically alloyed powders were consolidated after preheating at 450°C, and then heat treated isochronally for 1 hour to observe the microstructures and to investigate the mechanical properties. Stable phases of precipitates in the Al-Ti-Si and the Al-Ti-Zr alloys were identified as DO22-(Al,Si)_3Ti and Do_23-Al_3(Ti, Zr) each. Among the alloys, the mechanically alloyed Al-l0Ti-2Si alloy showed superior thermal stability and mechanical properties at elevated temperature. The additions of third elements, such as Si and Zr, to Al-Ti alloys seemed to improve the mechnical properties remarkably by stabilizing the microstructure and the precipitate phases in the consolidated alloys.

The Effect of Extrusion Temperature and Die Angle on Mechanical Properties of SiC_p/2024Al Composites Fabricated by Powder Extrusion Method: J Korean Powder Metall Inst. 1995;2(1):44-52.

Abstract PDF: Effects of the extrusion temperature and die angle on the tensile properties of SiCIyAl composites in powder extrusion have been investigated. SiCP/Al composites were extruded at various extrusion temperatures (450, 500, 550°C) under the extrusion ratio of 25 : 1. The ram speed was maintained at 13 cm/min for all the extrusion conditions. The surface of the extruded rod appeared to be smooth without tearing at 450 and 500°C, whereas it was very rough due to tearing at 550°C. It was found that the tensile strength and elongation of the composites extruded at 500°C are greater than those of composites extruded at 450°C This is due to the easier plastic deformation of composite extruded at 500°C, compared with the composites extruded at 450°C. The effect of die angle was examined under 20=60, 120, 180°die angles at extrusion temperature of 500°C under 25:1 extrusion ratio. The tensile strength of the composites extruded with 20=60°approved to be higher than that of the composties extruded with 28 : 120 and 180°This is attributable to the higher extrusion pressure, which mixed composite powders could be densely consolidated at elevated temperatures, resulting from high friction force between billet and sliding surface of conical die.

Transient-Liquid-Phase Bonding of Fe-Base MA956 ODS Alloy: J Korean Powder Metall Inst. 1995;2(1):53-62.

Abstract PDF: TLP(Transient-Liquid-Phase) bonding of Fe-base MA956 ODS alloy was performed. As insert metal a commercially available Ni-base alloy(MBF50) and an MA956 alloy with additive elements of 7wt% Si and 1wt% B were used. To confirm the idea that a concurrent use of MA956 powder with Insert metals can enhance the homogenization of constituent elements and thereby reduce the thickness of joint interface, MA956 powder was also inserted In a form of sheet. SEM observation and EDS analysis revealed that Cr-rich phase was formed in the bonded interface in initial stage of isothermal solidification during the bonding process, irrespective of kind of insert metals. Measurement of hardeness in the region of bonded interface and EDS analysis showed that a complete homogenization of composition could not be obtained especially in case of MBF50. Joints using either BSi insert metals only or BSi insert together with MA956 powder interlayer showed, however, a remarkable improvement in a compositional homogenization, even though a rapid grain growth in the bonded interface could not be hindered.

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