• Korean Journal of Materials Research
• /
• v.11 no.1
• /
• pp.34-38
• /
• 2001

Intermetallics of Fe-28%Al($Fe_3Al$) and Fe-28%Al-4%Cr($Fe_3Al-4Cr$) were oxidized at 1073, 1273 and 1473k in air for up to 17 days. The oxidation resistance of$Fe_3Al-4Cr$ was basically similar to or better than that of $Fe_3Al$. The oxide scales formed on $Fe_3Al$ consisted essentially of pure ${\alpha}-AL_2O_3$, while those formed on $Fe_3Al-4Cr$ consisted of ${\alpha}-AL_2O_3$ having dissolved iron and chromium ions. The preferential outward diffusion of substrate elements to form the outer oxide layer led to the formation of Kirkendall voids at the oxide-matrix interface. The scales formed on $Fe_3Al(-4Cr)$ were thin and dense up to 1273K, but they spalled easily at 1473K, accompanied by more weight gains.

• Journal of Powder Materials
• /
• v.12 no.1
• /
• pp.43-50
• /
• 2005

Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to Al-Fe-Cr and Al-Fe-Mo powder mixture to investigate effects of Cr and Mo addition on thermal stability of Al-Fe, and thereby to enhance its thermal stability up to $500^{\circC}$. Various analytical techniques including micro-Vickers hardness test, SEM, TEM, X-ray diffractometry and corrosion test were carried out. It was found that addition of Cr and Mo to Al-Fe system played a role of grain growth inhibitor of matrix Al and some precipitates such as $Al_3Fe$ during SPS and subsequent heat treatment. The inhibition of grain growth resulted in increased Vickers hardness and thermal stability up to $500^{\circC}$ comparing to those of Al-Fe alloy system.

• Korean Journal of Materials Research
• /
• v.12 no.11
• /
• pp.845-849
• /
• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Corrosion Science and Technology
• /
• v.3 no.3
• /
• pp.98-101
• /
• 2004

The corrosion behavior of Al-Fe coatings was studied in the wet-seal atmosphere of molten carbonate fuel cells (MCFC). Fe-8Al, Fe-16Al, Fe-25Al, Fe-36Al, and Fe-70Al (in at.%) specimens were tested in Li/K carbonate at $650^{\circ}C$ by a single cell test and an immersion test. In general, the corrosion resistance of the Al-Fe coatings was enhanced due to the formation of a protective $LiAlO_2$ layer. However, when the Al-Fe coatings didn't have sufficient content of aluminum enough for maintaining the protective layer, the corrosion resistance of the Al-Fe coatings was severely degraded by the growth of non-protective scales like $LiAlO_2$. The test results revealed that the aluminum contents in the coatings should be higher than 25 at.% in order to form and maintain the protective $LiAlO_2$ layers.

• Journal of Korea Foundry Society
• /
• v.8 no.4
• /
• pp.446-452
• /
• 1988

To obtain detailed information on the metastable and the equilibrium phases in rapidly solidified Al-(Fe,Ce) alloys, analysis of X-ray diffraction pattern has been carried out. It has been found that the metastable phase formed in Al-Fe alloys including up to 6wt%Fe is $Al_6Fe$ and the equilibrium phase is $Al_3Fe$. Any X-ray diffraction peak corresponding to the equilibrium phase $Al_{13}Fe_4$ has not been observed during aging. In Al-4wt%Fe alloy, which is ribbon shape with thickness less than $70\;{\mu}m$, aged at $400^{\circ}C$ for 1h after rapid solidification, unidentified phase has been found. In Al-4wt%Ce alloy, only X-ray diffraction peak corresponding to the equilibrium phase, $Al_4Ce$ has been observed. It has been found that the metastable phase Formed in Al-Fe-Ce alloys including up to 6wt% Fe and 4wt% Ce is $Al_6Fe$ and the equilibrium phases are $Al_3Fe$ and $Al_{10}CeFe_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.2
• /
• pp.185-190
• /
• 1999

An $Al_2O_3/Fe$ composite was synthesized through the double stage processes by a reaction sintering which requires simple process and equipments but provides near-net-shape, a reduction/oxidation process for 5 hrs at $650^{\circ}C$ was followed by sintering at $1200^{\circ}C$ to form an $Al_2O_3/Fe$ composite. The composite processed through the double stage sintering are mainly consists of $\alpha$-Fe and ${\alpha}Al_2O_3$ with minor amount of $FeAl_2O_4$, a spinnel structure which is known to prevent Fe from filling up the pores and good contact with $Al_2O_3/Fe$ particles.

• Journal of Korea Foundry Society
• /
• v.19 no.1
• /
• pp.71-76
• /
• 1999

Eutectic and off-eutectic Al-Fe alloys were unidirectionally solidified at the solidification rate of $1{\sim}50\;mm/min$ under the temperature gradients $75{\sim}80^{\circ}C/cm$. The investigation has been carried out for the microstructural variation, phase transition, mechanical properties by means of detailed analyses of stress-strain, micro-Vickers hardness and scanning electron micrography. The thermal stability at elevated temperature has been studied on $Al-Al_6Fe$ eutectic alloy held at $600^{\circ}C$ for $0{\sim}150$ hours. When the solidification rate was less than 10mm/min, the X-ray diffraction and EDS analysis showed the presence of $Al_3Fe$ compound. As the solidification rate more than 20 mm/min, $Al-Al_3Fe$ eutectic phase was transfered into $Al-Al_6Fe$ eutectic phase. The mechanical properties of unidirectionally solidified off-eutectic Al-Fe alloy is better than those of unidirectionally solidified eutecic Al-Fe alloy Maximum ultimate tensile strength was obtained in Al-2.25% Fe alloy which was unidirectionally solidified at the solidification rate of 20 mm/min. The metastable $Al-Al_6Fe$ phase was transferred into stable $Al-Al_3Fe$ phase at $600^{\circ}C$ held for 150 hours.

• Journal of Korea Foundry Society
• /
• v.33 no.3
• /
• pp.103-112
• /
• 2013

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were ${\alpha}$-Al, $Mg_2Si$, ${\alpha}-Al_{12}(Fe,Mn)_3Si$ and ${\beta}-Al_5FeSi$. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, ${\beta}-Al_5FeSi$ compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped ${\beta}-Al_5FeSi$ compound changed to chinese script ${\alpha}-Al_{12}(Fe,Mn)_3Si$. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, ${\beta}-Al_5FeSi$ phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from ${\beta}-Al_5FeSi$ phase to chinese script, ${\alpha}-Al_{15}(Fe,Mn)_3Si_2$ phase shape-modified from with high Mn/Fe ratio of the alloy.

• Journal of Korea Foundry Society
• /
• v.25 no.3
• /
• pp.128-133
• /
• 2005

The effects of Mn and Cr on the crystallization behaviors of Fe-bearing intennetallics in A356 alloy were studied. Coarse and acicular ${\beta}-Al_{5}$FeSi phase in A356-0.20wt.%Fe alloy was modified into small ${\alpha}$-Al(Fe,Mn)Si and ${\alpha}$-Al(Fe,Cr)Si phases in response to Mn and Cr addition, respectively. Increasing of Mn addition amount elevates the crystallizing temperature of ${\alpha}$-Al(Fe,Mn)Si and the Mn/Fe ratio in the ${\alpha}$-Al(Fe,Mn)Si. Cr is more effective to modify ${\beta}-Al_{5}$FeSi in comparison with Mn. ${\alpha}$-Al(Fe,Mn)Si phase had BCC/SC dual structure.

• Korean Journal of Metals and Materials
• /
• v.48 no.11
• /
• pp.981-988
• /
• 2010

The effects of Cr and Al contents in Fe-Al and Fe-Cr alloys on oxidation resistance, hardness, and the thermal expansion coefficient were investigated. Fe-Al and Fe-Cr alloys above 10wt.%Al and 20wt.%Cr contents have a high oxidation resistance. The hardness of the Fe-Al and Fe-Cr alloys increased with an increase in Al and Cr contents due to solid solution or formation of an intermetallic compound. The coefficients of thermal expansion of the Fe-Al alloys were higher than those of the Fe-Cr alloys because the coefficient of thermal expansion of Al was higher than that of Fe and Cr.