Wyniki wyszukiwania - BazTech

1

Microstructure Evolution of Ni-Based ODS Superalloy Powders During Horizontal Rotary Ball Milling

Lee H.-E., Kim Y. S., Park J. K., Oh S.-T.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1253--1255

EN

Microstructure evolution of Ni-based oxide dispersion-strengthened alloy powders with milling time is investigated. The elemental powders having a nominal composition of Ni-15Cr-4.5Al-4W-2.5Ti-2Mo-2Ta-0.15Zr-1.1Y2O3 in wt % were ball-milled by using horizontal rotary ball milling with the change of milling velocity. Microstructure observation revealed that large aggregates were formed in the early stages of ball milling, and further milling to 5 h decreased particle size. The average crystalline size, estimated by the peak broadening of XRD, decreased from 28 nm to 15 nm with increasing milling time from 1 h to 5 h. SEM and EPMA analysis showed that the main elements of Ni and Cr were homogeneously distributed inside the powders after ball milling of 5 h.

2

Fabrication of Cu-Based SiC Composites by Spark Plasma Sintering of Cu-Nitrate Coated SiC Powders

Jeong Y.-K., Kim Y. S., Oh S.-T.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 2B

1407--1410

EN

An optimum route to fabricate the Cu-based SiC composites with homogeneous microstructure was investigated. Three methods for developing the densified composites with sound interface between Cu and SiC were compared on the basis of the resulting microstructures. Starting with three powder mixtures of elemental Cu and SiC, elemental Cu and PCS coated SiC or PCS and Cunitrate coated SiC was used to obtain Cu-based SiC composites. SEM analysis revealed that the composite fabricated by spark plasma sintering using elemental SiC and Cu powder mixture showed inhomogeneous microstructure. Conversely, dense microstructure with sound interface was observed in the sintered composites using powder mixture of pre-coated PCS and Cu-nitrate onto SiC. The relationship between powder processing and microstructure was discussed based on the role of coating layer for the wettability.

3

Synthesis Of SiC/Cu Composite Powders From Polycarbosilane And Cupric Nitrate Trihydrate

Bang R.-S., Yim D.-M., Riu D.-H., Oh S.-T.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2B

1261--1263

EN

SiC/Cu composite powders with the barrier coating of SiC-Al onto SiC powders were synthesized from Al-containing polycarbosilane precursor and Cu-nitrate hydrate. Curing at 200°C and high temperature pyrolysis at 1600°C was used to achieve the crystallization of precursor, forming the SiC-Al coating on the surface of SiC powders. A core-shell structure with the core of SiC and the shell of Cu was constructed by calcination and hydrogen-reduction of Cu nitrate hydrate. XRD and SEM analysis revealed that the β-SiC and 4H-SiC phases were formed on the surface of the initial α-SiC powders. Also, it was observed by EDX mapping that core powders of SiC were homogeneously surrounded with the fine Cu particles on their surface.

4

Fabrication Of Porous Ti By Thermal Decomposition And Sintering Of PMMA/TiH2 Powder Compact

Jeon K. Ch., Kim Y. D., Suk M.-J., Oh S.-T.

Archives of Metallurgy and Materials

|

2015

|

Vol. 60, iss. 2B

1375--1377

EN

Porous Ti with controlled pore structure was fabricated by thermal decomposition and sintering process using TiH2 powders and Polymethylmethacrylates (PMMA) beads as pore forming agent. The beads sizes of 8 and 50 μm were used as a template for fabricating the porous Ti. The TiH2 powder compacts with 20 and 70 vol% PMMA were prepared by uniaxial pressing and sintered for 2 h at 1100°C. TGA analysis revealed that the PMMA and TiH2 were thermally decomposed at about 400°C forming pores and at about 600°C into metallic Ti phase. The porosity increased with increase in the amount of PMMA addition. Also, the microstructure observation showed that the pore size and shape were strongly dependent on the PMMA shapes.