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Journal : Makara Journal of Technology

Transmission Electron Microscopy Characterization of High-Temperatur Oxidation of Fe-20Cr-5Al Alloy Prepared by Focused Ion Beam Technique Dani, Mohammad; Untoro, Pudji; Putra, Teguh Yulius Surya Panca; Parikin, Parikin; Mayer, Joachim; Dimyati, Arbi
Makara Journal of Technology Vol. 19, No. 2
Publisher : UI Scholars Hub

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Abstract

The Focused Ion Beam (FIB) technique was applied for cross section preparation of the oxidized alloy for Transmission Electron Microscopy (TEM) study. Prior to preparation, the specimens of Fe-20Cr-5Al alloy sheet were oxidized in air at 1200 oC for 2 minutes, 10 minutes, 2 hours, and 100 hours. The microstructure and elemental composition of the samples were characterized using TEM equipped with an Energy Dispersive X-Ray Spectroscopy (EDX). The Electron Energy Loss Spectroscopy (EELS) was used to determine of the light elements. The TEM investigation reveals remarkable microstructure evolution of the specimens during oxidation which generally exhibit a typical multi-layer structure. The TEM images, however, can provide detailed description about the phases occur after oxidation such as the Tungsten (W) and the Gallium (Ga) layers on top of the samples obviously formed during FIB preparation, the formation of Al2O3 and Cr2O3 layer, MgAl2O4 spinel, porosity, Zr/Hf/Mg phases or clusters inside the oxide scale. Hence, the FIB technique has been proven to be reliable preparation technique for microstructural and elemental studies of Fe-20Cr-5Al alloy using TEM.
Comprehensive Inspection on the Experimental Ferritic Stainless Steel by Means of Transmission Electron Microscopy and Neutron Diffraction Techniques Parikin, Parikin; Dani, Mohammad; Iskandar, Riza; Jahja, Aziz Khan; Insani, Andon; Mayer, Joachim
Makara Journal of Technology Vol. 23, No. 3
Publisher : UI Scholars Hub

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Abstract

The field of physical metallurgy is one of the primary beacons that guide alloy developments for multipurpose materials such as the in-core structure materials for pressure vessel components and heat exchangers. The surface microstructure of new ferritic steel with significant local constituent materials was characterized by high resolution powder neutron diffractometer (HRPD) and transmission electron microscope (TEM), combined with the energy dispersive X-ray spectroscopy (EDX). The alloy contains73% Fe, 24% Cr, 2% Si, 0.8% Mn, and 0.1% Ni, in %wt. The charge materials were melted by the casting techniques. The neutron diffractograms obtained shows five dominant diffraction peaks at (110), (200), (211), and (220) reflection planes, which is a typical structure for a body centered tetragonal system. The pattern also included some unidentified peaks which were verified to be Al2O3.54SiO2, Cr23C6, and SiC crystals. A piece of alloy which taken from the middle of the ferritic ingots was also characterized by the HRPD; no unidentified peaks were observed. Results from the scanning transmission electron microscopy (STEM) combined with EDX analyses confirmed the neutron identified phase distributions. Also, oxides and carbides were observed to form mainly close to the surface of the steel. Cracks and pores which probably formed during the preparations were also identified close to the surface. Although the ferritic steel was successfully synthesized and characterized, some unidentified phases and defects could still be found in the produced ingots.