• 한국주조공학회지
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• 제28권2호
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• pp.64-68
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• 2008

The microstructure of Cu-Mg-P base alloys were significantly affected by small amounts of Fe and Co additions, however the tensile properties and electrical conductivity of the Cu alloys were mainly determined by the fabrication process. Relatively high electrical conductivity (> 80% IACS) was obtained in the all Cu-Mg-P based alloys when they were finally aged at $480^{\circ}C$. Tensile properties could be significantly enhanced by final cold rolling, especially at extremely low temperatures. Softening of cold-rolled alloys took place at about $450^{\circ}C$ owing to recovery and recrystallization, but it was delayed up to $500^{\circ}C$ in the Fe-added alloy.

• 대한금속재료학회지
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• 제48권5호
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• pp.436-444
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• 2010

The hot tear susceptibility of Al alloys was investigated by using a constrained-rod mold designed to quantify 8 types of tear tendency. The severity of the crack was scored by 5 grades on a scale of 0 to 4, with 0 being "no crack formed" and 4 being "complete separation by crack". The Hot Tear Susceptibility index (HTS) which consists of crack type scores and position scores, was proposed to compare the hot tear tendency of Al alloys. A356.0 cast alloy and AA6061 wrought Al alloy showed an HTS value of 27.5 and 53 respectively. The effects of Si, Cu, and Mg content on hot tear tendency were also investigated with a constrained-rod mold. The variation of HTS values with alloying elements represents similar behavior in the variation of the solidification range in a pseudo binary phase diagram.

• 한국주조공학회지
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• 제33권4호
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• pp.171-180
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• 2013

The effects of alloying elements on the solidification characteristics, microstructure, thermal conductivity, and tensile strength of Al-Zn-Mg-Fe alloys were investigated for the development of high strength and high thermal conductivity aluminium alloy for die casting. The amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the liquidus/solidus temperature, the latent heat for solidification, the energy release for solidification and the fluidity of Al-Zn-Mg-Fe alloys. Thermo-physical modelling of Al-Zn-Mg-Fe alloys by the JMatPro program showed $MgZn_2$, AlCuMgZn and $Al_3Fe$ phases in the microstructure of the alloys. Increased amounts of Mg in Al-Zn-Mg-Fe alloys resulted in phase transformation, such as $MgZn_2{\Rightarrow}MgZn_2+AlCuMgZn{\Rightarrow}AlCuMgZn$ in the microstructure of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys resulted in a gradual reduction of the thermal conductivity of the alloys. Increased amounts of Zn and Mg in Al-Zn-Mg-Fe alloys had little effect on the tensile strength of the alloys.

• Journal of Welding and Joining
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• 제18권2호
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• pp.86-94
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• 2000

This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7N01 spot-welded by pulse Nd : YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed : center line crack({TEX}$C_{C}${/TEX}), diagonal crack({TEX}$C_{D}${/TEX}), and U shape crack({TEX}$C_{U}${/TEX}). Also, HAZ crack({TEX}$C_{H}${/TEX}) was observed in the HAZ region, furthermore, mixing crack({TEX}$C_{M}${/TEX}) consisting of diagonal crack and HAZ crack was observed. White film was formed at th hot crack region in the fractured surface after it was immersed to 10% NaOH water. In the case of A5083 alloy, white films in {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack region were composed of low melting phases, {TEX}$Fe_{2}SiAl_{8}${/TEX} and eutectic phases, $Mg_2$Al$_3$ and $Mg_2$Si. Such films observed $CuAl_2$, {TEX}$Mg_{32}(Al,Zn)_{3}${/TEX}, MgZn$_2$, $Al_2$CuMg and $Mg_2$Si were observed in the whitely etched films near {TEX}$C_{C}${/TEX} crack and {TEX}$C_{D}${/TEX} crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Sim in the case of A7N01 alloy, respectively. The {TEX}$C_{C}${/TEX} and {TEX}$C_{D}${/TEX} cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of {TEX}$C_{M}${/TEX} crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The {TEX}$C_{U}${/TEX} crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification.

• 한국주조공학회지
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• 제42권6호
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• pp.337-346
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• 2022

본 연구에서는 Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu 합금의 용체화 처리 조건 최적화를 위해 545℃ 온도 조건에서 최대 7시간까지 용체화 처리를 수행한 후 광학현미경 및 FE-SEM을 활용한 미세조직 관찰 및 브리넬 경도 측정을 수행하였다. 합금 내 공정 Si 상은 용체화 처리 초반 3시간 동안 급격한 조대화 현상을 나타내었으며, 이후에는 용체화 처리가 진행되어도 Si 상 크기는 크게 변화하지 않았다. 한편 공정 Si 상의 구상화의 경우, 용체화 처리 시간이 7시간에 도달할 때 까지 지속적으로 진행되었다. Cu가 첨가된 합금의 주방상태에서는 Q-Al₅Cu₂Mg₈Si₆ 상과 θ-Al₂Cu 상이 확인되었으나, 545℃에서 3시간 동안 진행된 용체화 처리 이후에는 모두 분해되었다. 주방상태에서 확인된 π-Al₈FeMg₃Si 상은 5시간의 용체화 처리 이후에 사라지거나(0.3wt%Mg) 혹은 7시간의 용체화 처리 이후에도 존재(0.5wt%Mg)하였다. 초정 α상 내 Mg 및 Cu 함량은 용체화 처리 시간이 5시간에 도달할 때 까지 증가하였으며, 이는 Mg 및 Cu를 함유한 금속간 화합물의 용체화 시간에 따른 분해 거동과 일치하였다. Al-7Si-Mg-Cu 합금의 용체화 처리 과정에서 확인한 미세조직 변화를 종합적으로 고려할 때, 본 연구에서 다룬 합금의 석출강화 효과 극대화를 위해서는 545℃ 조건에서 최소 5시간의 용체화 처리가 필요한 것으로 판단되며, 용체화 처리 조건 별로 측정된 브리넬 경도 데이터로부터 동일한 최적 용체화 처리 조건을 도출할 수 있었다.

• 한국군사과학기술학회지
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• 제14권6호
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• pp.1018-1025
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• 2011

The improved properties of corrosion for 90Cu10NiFe alloy in natural seawater were explained by sodium diethyl dithio carbamate(NaDDC), namely organic compound, which is reagent for heavy metal extractions of waste water. The efficiency of NaDDC as corrosion inhibitor for 90Cu10NiFe alloy has been investigated in seawater after immersion in various concentrations of NaDDC solutions for 12~36hrs at pH 8.2 by weight loss test and electrochemical techniques including potentiodynamic polarization and SEM-EDS measurements. The results showed that the corrosion resistance of 90Cu10NiFe alloy improves with the increasing concentration of NaDDC but it did not improves with increasing time any more, so the highest inhibition efficiency was 93% at 100mg/L, 36hrs. The results obtained from weight losses and corrosion rates in polarization curve measurements were in good agreement. Therefore, it showed that NaDDC is a good inhibitor for copper corrosion of 90Cu10NiFe alloy.

• 한국주조공학회지
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• 제17권6호
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• pp.545-551
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• 1997

14 cm length Al-15Cu-1Mg alloys have been directionally solidified in 3 mm diameter alumina tubes in a furnace moved with a constant velocity V=12 cm/hr under various furnace temperatures of 660, 710 and $760^{\circ}C$. By analysing the evolution of the temperature profiles along the alloy length during the solidification, the growth characteristics such as the position of the solid/liquid interface, the local growth velocity (R) and the temperature gradient at the solid/liquid interface (G) have been determined. The effects of the furnace temperature on the growth behavior have been investigated by the comparison of R and G values for each temperature. Under the furnace temperature of $760^{\circ}C$, steady state growth region was observed for the latter half of the growth period.

• Applied Microscopy
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• 제16권2호
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• pp.14-24
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• 1986

The interrelation of secondary defects, intermediate S' phase and aging condition in Al-2.0 wt% Cu-1.1 wt% Mg alloy is studied by transmission electron microscope. The results obtained in this study are as follows. 1. High density of dislocation loops, helices and stacking faults are observed in this specimen with aging treatment. 2. The number of dislocation loops and the width of loop free zone (LFZ) are increased with aging time. 3. The intermediate S' phase precipitates and grows on the dislocations and secondary defects. 4. The misfit dislocations are formed around intermediate S' phase. 5. It is thought that the helices appear to be produced by the climb of screw dislocations, while the dislocation loops appear to be formed both by condensation of vacancies into collapsed discs and by interaction of helices with screw of opposite sign.

• 열처리공학회지
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• 제3권1호
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• pp.8-16
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• 1990

Effects of thermomechanical treatments(TMT) on the microstructures and mechanical properties in Al-2.27%, Li-1.28%, Cu-0.63%, Mg-0.12%, Zr alloy were investigated. The TMT process improved the tensile strength. Growth of ${\delta}^{\prime}$, S' and $T_1$ phases was restrained by TMT processes while the density of ${\delta}^{\prime}$, S' and $T_1$ phases was increased by TMT processes. The TMT treated specimens tend to fail in inter-subboundary mode. The increases of strength by the T-HA processes were compared to those of the T-AHA processes.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.377-381
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• 2004

Electrical conductivity of Al-Si-Cu-Mg alloy foams of various density produced in powder metallurgical method has been measured using two probe electrical conductivity measurement method. Compressive mechanical properties such as elastic modulus and plastic plateau stress of foams were evaluated from electrical conductivity using power law relation and scaling laws of foam properties. Uni-axial compression test was also performed. Experimentally measured elastic modulus and plastic plateau stress were compared with the values evaluated from electrical conductivity. The computed values were in good agreement with the experimental result.