희생양극 하에서 알루미늄의 해수 부식 거동

김종수(Jongsoo Kim),김희산(Heesan Kim) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.1

Al-Mg alloy, an open rack vaporizer(ORV) material was reported to be corroded in seawater environments though the ORV material was coupled to thermally sprayed Al-Zn alloy functioning a sacrificial anode. In addition, the corrosion behavior based on the calculated corrosion potential did not match the observed corrosion behavior. Hence, the goal of this study is to get better understanding on Al or Al-Mg alloy coupled to Al-Zn alloy and to provide the calculated corrosion potential representing the corrosion behavior of the ORV material by immersion test, electrochemical tests, and calculation of corrosion and galvanic potential. The corrosion potentials of Al and Al alloys also depended on alloying element as well as surface defects. The corrosion potentials of Al and Al-Mg alloy were changed with time. In the meantime, the corrosion potentials of Al-Zn alloys were not. The corrosion rates of Al-Zn alloys were exponentially increased with zinc contents. The phenomena were explained with the stability of passive film proved by passive current density depending on pH and confirmed by the model proposed by McCafferty. Dissimilar material crevice corrosion (DMCC) test shows that higher content of zinc caused Al-Mg alloy corroded more rapidly, which was due to the fact that higher corrosion rate of Al-Zn makes [H?] and [Cl?] more concentrated within pit solution to corrode Al-Mg alloy. Considering electrochemical reactions within pit as well as bulk in the calculation gives better prediction on the corrosion behavior of Al and Al-Mg alloy as well as the capability of Al-Zn alloy for corrosion protection.

Ti-Al-Fe계 합금의 고온산화거동에 미치는 Fe의 영향

윤장원,현용택,김정한,염종택,윤석영,Yoon, Jang-Won,Hyun, Yong-Taek,Kim, Jeoung-Han,Yeom, Jong-Taek,Yoon, Seog-Young 한국재료학회 2011 한국재료학회지 Vol.21 No.7

In this paper, high temperature oxidation behavior of newly developed alloys, Ti-6Al-4Fe and Ti-6Al-1Fe, is examined. To understand the effect of Fe on the air oxidation behavior of the Ti-Al-Fe alloy system, thermal oxidation tests are carried out at $700^{\circ}C$ and $800^{\circ}C$ for 96 hours. Ti-6Al-4V alloy is also prepared and tested under the same conditions for comparison with the developed alloys. The oxidation resistance of the Ti-Al-Fe alloy system is superior to that of Ti-6Al-4V alloy. Ti-6Al-4V shows the worst oxidation resistance for all test conditions. This is not a result of the addition of Fe, but rather it is due to the elimination of V, which has deleterious effects on high temperature oxidation. The oxidation of the Ti-Al-Fe alloy system follows the parabolic rate law. At $700^{\circ}C$, Fe addition does not have a noticeable influence on the amount of weight gain of all specimens. However, at $800^{\circ}C$, Ti-6Al-4Fe alloy shows remarkable degradation compared to Ti-6Al-1Fe and Ti-6Al. It is discovered that the formation of $Al_2O_3$, a diffusion resistance layer, is remarkably hindered by a relative decrease of the ${\alpha}$ volume fraction. This is because Fe addition increases the volume fraction of ${\beta}$ phase within the Ti-6Al-xFe alloy system. Activities of Al, Ti, and Fe with respect to the formation of oxide layers are calculated and analyzed to explore the oxidation mechanism.

고신율 금형주조용 Al-9wt%Si-Mg계 합금의 주조특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ),정창열 ( Chang Yeol Jeong ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.6

Effect of Fe and Mn contents on the castability of Al-9wt%Si-xMg-yFe-zMn alloy has been studied. The alloy was composed of α-Al phase, Al+eutectic Si phase, β-Al5FeSi compound and chinese script α-Al15(Mn,Fe)3Si2 compound. β-Al5FeSi and α-Al15(Mn,Fe)3Si2 compounds assumed to effect the fluidity and shrinkage behaviors of the alloy during solidification due to the crystallization of α-Al15(Fe,Mn)3Si2 and β-Al5FeSi compounds above eutectic temperature. As Fe and Mn contents of Al-9wt%Si- 0.3wt%Mg system alloy increased from 0.15wt% to 0.6wt% and from 0.3wt% to 0.7wt%, fluidity of the alloy decreased by 5.7% and 3.3%, respectively. And as Mg content of Al-9wt%Si-0.45wt%Fe-0.5wt%Mn system alloy increased from 0.3wt% to 0.4wt%, fluidity of the alloy decreased by 8.6%. When Fe content of the alloy increased from 0.15wt% to 0.6wt%, macro shrinkage ratio decreased from 6.1% to 4.1%, and micro shrinkage ratio increased from 0.04% to 0.24%. Similarly, Mn content of the alloy increased from 0.3wt% to 0.7wt%, macro shrinkage ratio decreased from 6.0% to 4.5% and micro shrinkage ratio increased from 0.12% to 0.18%. Judging from the castability of the alloy, Al-9wt%Si-0.3wt%Mg alloy with low content of Fe and Mn, 0.1wt% Feand 0.3wt% Mn, is recommendable.

개량 Al-0.7Mn 합금의 미세조직, 고온 변형 거동 및 성형성

강태훈,황원구,신영철,최호준,노흥렬,이기안 한국소성∙가공학회 2022 소성가공 : 한국소성가공학회지 Vol.31 No.6

The microstructure and high-temperature plastic deformation behavior of the modified Al-0.7Mn alloy were investigated and compared with the conventional Al-0.3Mn (Al3102) alloy. α-Al (matrix) and Al6(Mn, Fe) phases were identified in both alloys. As a result of microstructure observation, both alloys showed equiaxed grains, and Al-0.7Mn alloy showed larger grain size and higher Al6(Mn, Fe) fraction than Al-0.3Mn alloy. High temperature compressive tests, the deformation temperatures of 410℃, 450℃, 490℃, 530℃ and strain rats of 10-2/s, 10-1/s, 1/s, 10/s, were conducted using Gleeble equipment. The flow stress values of Al-0.7Mn alloy were higher than that of Al-0.3Mn alloy at all strain rates and temperature conditions. Constitutive equations were presented using the flow stresses obtained from experimental results and the Zener-Hollomon parameter. In the true stress-true strain curves of the two alloys, the experimental and predicted values were in good agreement with each other. Based on the dynamic material model, eutectic deformation maps of Al-0.7Mn and Al-0.3Mn alloys were suggested, and the plastic instability region was presented. The modified Al-0.7Mn alloy showed a wider plastic instability region than that Al-0.3Mn alloy. Based on the process deformation maps, the MPE tube parts could be manufactured through the actual extrusion process using the suggested conditions.

Effect of Strain Induced Melt Activation Process on the Microstructure and Mechanical Properties of Al-5Ti-1B Treated Al-7Si Alloy

Chandan Choudhary,H. N. Bar,A. K. Pramanick,K. L. Sahoo,Durbadal Mandal 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

In this study, simultaneous effects of modified strain induced melt activation (M-SIMA) process and addition of Al-5Ti-1Bchemical grain refiner on the casting defects, microstructural features, and mechanical properties of hypoeutectic Al-7Sialloys are investigated. The traditional melting and casting techniques were used to develop cast ingots of unrefined andgrain refined structures of Al-7Si alloy. Addition of chemical refiner Al-5Ti-1B to Al-7Si melt could significantly changethe secondary dendritic arm spacing and eutectic Si particle size to 31% and 28%, respectively. In the M-SIMA process, castingots were 60% warm deformed and heat-treated at mushy zone at temperature 585 °C for 30 min. Spherical morphology ofα-Al grain and fine fibrous type eutectic Si are observed after M-SIMA process. Grain size of α-Al and eutectic Si are furtherreduced to 56% and 40% after M-SIMA process of grain refined Al-7Si alloy. Porosity and micro-cracks are also minimizedafter M-SIMA process. Microstructural features of cast and M-SIMA processed alloys were characterized through opticaland scanning electron microscopy. X-ray diffraction techniques reveal the different phases present in the developed alloy. TEM analysis further confirms the presence of TiAl3and Ti7Al5Si14precipitates in grain refined Al-7Si alloy. A significantimprovement of 132% in hardness (HV), 76% in yield strength, 120% in ultimate tensile strength, 125% in elongation tofracture, and 116% in specific ultimate tensile strength are obtained in M-SIMA processed grain refined Al-7Si alloy. Fractographyanalysis reveals the mixed mode of fracture in M-SIMA processed Al-7Si alloy with refined structure comparedto brittle fracture of unrefined cast alloy.

고압 금형 주조용 Al-4 wt%Mg-0.9 wt%Si계 합금의 인장특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.3

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 α-Al, Mg2Si, α-Al12(Fe,Mn)3Si and β-Al5FeSi. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, β-Al5FeSi compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped β-Al5FeSi compound changed to chinese script α-Al12(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, β-Al5FeSi 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 β-Al5FeSi phase to chinese script, α-Al15(Mn,Fe)3Si2 phase shape-modified from with high Mn/Fe ratio of the alloy.

Al-5Mg 합금의 내산화성 및 인장특성에 미치는 Al2Ca의 영향

하성호 ( Seong Ho Ha ),윤영옥 ( Young Ok Yoon ),김세광 ( Shae K. Kim ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.6

The effect of Al2Ca on the oxidation resistance and tensile property of Al-5Mg alloys was investigated. According to the TGA (Thermogravimetric analysis) result at 550oC after 24hrs, the Al-5Mg alloy showed parabolic behavior with weight gain. On the other hand, there was almost no difference in the weight changes of the Al2Ca added Al-5Mg alloys during the oxidation. It was thought that the improvement of oxidation resistance in Al2Ca added Al-5Mg alloys might be due to the formation of a protective oxide layer with CaO and MgO on the surface. The microstructures of the alloys showed grain refinement with an increasing Al2Ca content. From the tensile test, the yield strength of the alloys were improved with an increasing Al2Ca content. The 0.07 mass%Al2Ca added Al-5Mg alloy showed similar elongation and increased strength, simultaneously. It was considered that the addition of Al2Ca, which was superior in the oxidation resistance of Al, reduced the formation of Mg oxides and inclusions during the alloying. This, partly led to the improvement of tensile properties.

선체 재료용 Al-Mg 합금과 Al-Mg-Si 합금의 해수 내 캐비테이션 특성

김성종 ( Seong Jong Kim ),김규환 ( Kyu Hwan Kim ),이승준 ( Seung Jun Lee ) 한국부식방식학회 2011 Corrosion Science and Technology Vol.10 No.4

Al alloys have been used widely for commercial and military ships in most ocean countries since mid-1950s, and the value as light metal with high mechanical strength has been proven. As the safety and fuel efficiency of Al ships have improved, she can carry more freight, sail faster and travel longer distances. Furthermore, in the shipbuilding industry, Al alloys are applied as structural materials for ships to various areas including the deck of luxurious cruises, battleships and leisure ships. In addition, Al alloys are being spotlighted as environmental-friendly material as they can be recycled even after end of lifespan. However, Al alloys for ships must be carefully selected after considering corrosion resistance, endurance, strength, and weldability in sea water environment. Al alloys to satisfy these conditions are used widely include 5000 series Al-Mg alloy and 6000 series Al-Mg-Si alloy. Thus, this study selected and evaluated the cavitation characteristics of the 5000 series Al alloys that are used in hulls that directly contact seawater and the 6000 Al alloys that are used in the upper structures of ships. Results of cavitation test with time, weightloss and cavitation rate of 5456-H116 showed the smallest damage among 5052-O, 5456-H116 and 60691-T6.

Tensile and High-Cycle Fatigue Properties of Extruded AZ91–0.3Ca–0.2Y Alloy with Excellent Corrosion and Ignition Resistances

Jae Won Cha,Ye Jin Kim,Young Min Kim,Jun Ho Bae,Sung Hyuk Park 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2

Mg–Al–Zn–Ca–Y (SEN) alloys have been recently developed by adding small amounts of Ca and Y to commercial Mg–Al–Zn (AZ series) alloys. These alloys possess superior corrosion and ignition resistances to their commercial AZ seriescounterparts. Here, commercial AZ91 (Mg–9Al–0.8Zn, wt%) and developed SEN9 (Mg–9Al–0.8Zn–0.3Ca–0.2Y, wt%)alloys are extruded under the same conditions, and the microstructure, tensile properties, and high-cycle fatigue propertiesof the extruded alloys are compared. The extruded SEN9 alloy has a smaller average grain size and higher microstructuralhomogeneity than the extruded AZ91 alloy because the Al2Y,Al2Ca,and Al8Mn4Yparticles in the homogenized SEN9 billetpromote dynamic recrystallization during extrusion. Despite their different microstructures, the two alloys possess similartensile strengths because the strong precipitation hardening in the extruded AZ91 alloy is offset by strong grain-boundaryhardening in the extruded SEN9 alloy. However, the extruded SEN9 alloy exhibits higher tensile elongation because deformationtwinning is suppressed by the finer grains. The fatigue strength of the extruded SEN9 alloy (100 MPa) is slightlylower than that of the extruded AZ91 alloy (110 MPa). For the extruded AZ91 alloy, fatigue cracks initiate on the surfacein all specimens, whereas for the extruded SEN9 alloy, fatigue cracks initiate in an Al2Caor Al2Yparticle present on thesubsurface in some specimens, especially at low stress amplitudes. The Al2Caand Al2Yparticles are larger than the Mg17Al12precipitates, and considerably harder than the matrix. Consequently, local stress is highly concentrated in these particlesduring cyclic loading, which eventually causes premature fatigue cracking and decreased fatigue resistance.

Milling and Particulate Characteristics of Al Alloy-Al₂O₃ Powder Mixtures for Reaction-Bonded Al₂O₃(RBAO) Process

Lee, Hyun-Kwuon Materials Research Society of Korea 2013 한국재료학회지 Vol.23 No.10

The milling and particulate characteristics of Al alloy-$Al_2O_3$ powder mixtures for a reaction-bonded $Al_2O_3$ (RBAO) process were studied. A commercially available prealloyed Al powder with Zn, Mg, Cu and Cr alloying elements (7475 series) was mixed with a calcined sinter-active $Al_2O_3$ powder and then milled in centrifugal milling equipment for ~48 hrs. The Al alloy-$Al_2O_3$ powder mixtures after milling were characterized and evaluated in various ways to reveal their particulate characteristics during milling. The milling efficiency of the Al alloy increased with a longer milling time. Comminution of the Al alloy particles started with its elongation, showing a high aspect ratio. With a longer milling time, the elongated Al alloy particle changed in terms of its shape and size, becoming equiaxially fine particles. Regardless of the milling efficiency of the Al alloy particles, all of the Al alloy particles repeatedly experienced strong plastic deformation during milling, giving rise to higher density of surface defects, such as microcracks, and leading to higher residual microstress within the Al alloy particles. The chemical reactions, oxidation behavior and hydration behavior of the Al alloy particles and the hydrolysis characteristics of their reaction with the environment were also observed during the milling process and during the subsequent powder handling steps.