• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.839-844
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• 2011

We examined the effects of alloying elements such as Fe, Ga, In, Sn, Mg, and Mn on the electrochemical characteristics of Al-based alloys for Al-air batteries by potentiodynamic polarization tests and electrochemical impedance spectroscopy. The corrosion potential of an Al anode was lowered by the addition of Ga and Sn, resulting in an increase in the cell voltage compared with a pure Al electrode. Fe was not beneficial to improve the electrochemical properties of the Al anode in that it caused a decrease in the cell voltage and reduced corrosion rate slightly. In, Mn, Sn, and Mg decreased the corrosion rate of the Al alloys, while Ga enhanced corrosion significantly and accelerated consumption of the anode.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.166-177
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• 1997

The high strength AlZnMgCu0.5 alloy is a light metal with good age hardenability, and has a high tensile and yielding strength. Therefore, it can be used for structures requiring high speciple strength. Even though high strength AlZnMgCu alloy has good mechanical properties, it has a lot of problems in TIG and MIG welding processes. Since lots of high heat absorption is introduced into the weldment during TIG and MIG processes, the microstructural variation and hot cracks take place in heat affected zone. Therefore, the mechanical properties of high strength AlZnMgCu0.5 alloy can be degraded in weldment and heat affected zone. Welding process utilizing high density heat source such as electron beam should be developed to reduce pore and hot cracking, whichare usually accompanied by MIG and TIG welding processes. In this work, electron beam welding process were used with or without AlMg4.5Mn as filler material to avoid the degradation of mechanical properties. Mechanical and metallurgical characteristics were also studied in electron beam weldment and heat affected zone. Moreover hot cracking mechanism was also investigated.

• Journal of Korea Foundry Society
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• v.24 no.3
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• pp.138-144
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• 2004

Effects of alloying elements such as Si, Mn, Zn on the fluidity and mechanical properties of high ductility Al-Mg based alloys were investigated. The fluidity of alloys was evaluated using a vacuum suction fluidity test, and Si addition was observed to increase the fluidity of AI-Mg binary alloys substantially while Zn somewhat decreased the fluidity. However, both the strength and ductility were significantly deteriorated by the Si additions. It was observed that a small amount of Mn addition to Al-Mg alloy increased the tensile strength effectively without losing much ductility but the effect of Zn addition on the strength was relatively small.

• Journal of Welding and Joining
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• v.13 no.3
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• pp.134-146
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• 1995

Aluminium nitride(AlN) is currently under investigation as potential candidate for replacing alumium oxide(Al$_{2}$ $O_{3}$) as a substrate material for for electronic circuit packaging. Brazing of aluminium nitride(AlN) to Cu with Ag base active alloy containing Ti has been investigated in vacuum. Binary Ag$_{98}$ $Ti_{2}$(AT) and ternary At-1wt.%Al(ATA), AT-1wt.%Ni(ATN), AT-1wt.% Mn(ATM) alloys showed good wettability to AlN and led to the development of strong bond between brate alloy and AlN ceramic. The reaction between AlN and the melted brazing alloys resulted in the formation of continuous TiN layers at the AlN side iterface. This reaction layer was found to increase by increase by increasing brazing time and temperature for all filler metals. The bond strength, measured by 4-point bend test, was increased with bonding temperature and showed maximum value and then decreased with temperature. It might be concluded that optimum thickness of the reaction layer was existed for maximum bond strength. The joint brazed at 900.deg.C for 1800sec using binary AT alloy fractured at the maximum load of 35kgf which is the highest value measured in this work. The failure of this joint was initiated at the interface between AlN and TiN layer and then proceeded alternately through the interior of the reaction layer and AlN ceramic itself.

• Journal of Welding and Joining
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• v.33 no.5
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• pp.31-34
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• 2015

Microstructure and tensile property in the weld heat-affected zone (HAZ) of austenitic Fe-Mn-Al-C low density steels were investigated through transmission electron microscopy analysis and tensile tests. The HAZ samples were prepared using Gleeble simulation with high heat input welding condition of 300 kJ/cm, and the HAZ peak temperature of $1200^{\circ}C$ was determined from differential scanning calorimetry (DSC) test. The strain- stress responses of base steels showed that the addition of V improved the tensile and yield strength by grain refinement and precipitation strengthening. Tensile strength and elongation decreased in the weld HAZ as compared to the base steel, due to grain growth, while V-added steel had a higher HAZ strength as compared than V-free steel.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.448-453
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• 2011

Pre-aging heat treatment after solution heat treatment (SHT) of Al-0.4 wt%Mg-1.2 wt%Si-0.1 wt%Mn alloy sheets for auto-bodies was carried out to investigate the effect of pre-aging and its conditions on the bake-hardening response. Mechanical properties were evaluated by a tensile and Vickers hardness test. Microstructural observation was also performed using a transmission electron microscope (TEM). It was revealed that pre-aging treatments play a great role in the bake-hardening response. In addition, it was found that the sphere-shaped nanosized clusters that can directly transit to the needle-shaped ${\beta}$" phase during the paint-bake process, not being dissolved into the matrix, are formed at 343 K. The result, reveals that the dominant factor of the bake-hardening response is the pre-aging temperature rather than the pre-aging time.

• Journal of Korean Vacuum Science & Technology
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• v.4 no.3
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• pp.68-72
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• 2000

We have deposited Mn on Pd(oon) at RT up to 30 ML. LEED pattern changed from p($1{\times}1$) to c($2{\times}2$) order below 0.5 ML Mn deposition. During Mn deposition, we have not found any changes in the peak position and the intensity of LEED I/V curve. Using LEED I/V curve analysis for each coverage, we found atomic structure and surface composition of c($2{\times}2$) ordered Mn alloy on Pd(001) surface. Above 1 Ml Mn, in the first layer the Mn subplane lies above the Pd subplane by 0.32 ${\AA}$. This result is very different from the earlier result of Jona et al., who contended that after annealing at 200 for 2 min, a buckled first layer with the Mn subplane lower than the Pd subplane by 0.2 ${\AA}$.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.201-205
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• 2008

In order to investigate the origin of the band gap in the half-metallic Heusler alloy, $Co_2MnSi$, through the electronic structure calculation, we have calculated the electronic structures for the compounds consisted of parts of Heusler structures, i.e. zinc-blende CoMn, half-Heusler CoMnSi, and artificial $Co_2Mn$, using the full-potential first-principles band calculation method. By investigating the band hybridization and energy gap for the calculated density of states for these compounds, we found that the the origin of the band gap is not consistent with the explanation discussed by Galanakis et al. We have also discussed the magnetism for these compounds by the calculated number of majority- and minority-spin electrons.

• Transactions of Materials Processing
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• v.31 no.3
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• pp.160-166
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• 2022

The purpose of this study is to investigate the effects of combined addition of Ca and Y on the precipitation and age-hardening behavior of an extruded AZ91 alloy by conducting the aging treatment at 200 ℃ for hot-extruded AZ91 and AZ91-0.3Ca-0.2Y alloys. In the AZ91 alloy, many Mg₁₇Al₁₂ discontinuous precipitate (DP) bands formed during air cooling immediately after extrusion are present, whereas in the AZ91-0.3Ca-0.2Y alloy, a few DP bands and numerous Al₂Y, Al₈Mn₄Y, and Al₂Ca phase particles are distributed along the extrusion direction. The peak-aging time of the AZ91-0.3Ca-0.2Y alloy is 16 hours, twice that of the AZ91 alloy. Although both alloys have similar hardness before aging treatment, the hardness after peak-aging treatment (i.e., peak hardness) of the AZ91-0.3Ca-0.2Y alloy is higher than that of the AZ91 alloy, as 93.1 and 88.7 Hv, respectively. The microstructures of both peak-aged alloys comprise DPs and continuous precipitates (CPs). However, the peak-aged AZ91-0.3Ca-0.2Y alloy has a smaller amount of DPs and a larger amount of CPs than the peak-aged AZ91 alloy. Additionally, the inter-particle spacings of DPs and CPs in the former are significantly narrower than those in the latter. These results demonstrate that the addition of small amounts of Ca and Y to a commercial AZ91 alloy considerably affects the formation rate, size, and amount of CPs and DPs during aging and resultant age-hardening behavior.

• Transactions of the Korean hydrogen and new energy society
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• v.5 no.1
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• pp.1-8
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• 1994

Lattice structure, hydrogen absorption characteristics, discharge capacity and cycle life of $V_{22}Ti_{16}Zr_{16}Ni_{39}X_7$(X= Cr, Co, Fe, Mn, Al) alloys were investigated. The matrix phases of these alloys were the C14 Laves phase. Chromium-containing alloy had a vanadium-rich phase in addition to the Laves phase. The chromium, maganese, or aluminum-containing alloys had lower hydrogen equilibrium pressure and larger hydrogen absorption content than the cobalt or iron-containing alloys. The discharge capacities of these alloys were 270~330mAh/g. The discharge capacity according to the alloying element X decreased in the order of Mn>Cr>Co, Al)Fe. The charge/discharge cycle lives of the chromium, cobalt or iron-containing alloys were longer than those of maganese or aluminum-containing alloys due to the lower vanadium dissolution rate.