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1
Content available Study on Improvement of Surface Properties of SKD61 Powder on S45C Using Laser Cladding
100%
Kim C.-W. , Yoo H.-S.
Archives of Metallurgy and Materials
|
2022
|
tom Vol. 67, iss. 4
1465--1468
EN
In this study, we investigated the effect of cladding on structural carbon steel (S45C) using 5%Cr-1.5%Mo-Fe powder (SKD61), which is expected to show economically efficient production of die-casting parts. The process conditions were performed under argon atmosphere using a diode laser source with specialized wavelength of 900-1070 nm, and the output conditions were 3, 4, and 5 kW, respectively. After the cladding was completed, the surface coating layer’s shape and the microstructure were analyzed. The hardness test was carried out with Micro Vickers hardness tester under 500 gram-force along the normal line at the interval of 0.2 mm from the surface to core direction on the cross-sectional area. In addition, polarization curve test of the surface coating layer was performed to investigate the corrosion resistance characteristics.
2
Content available Effect of Fe Content on the Mechanical Properties and Thermal Conductivity of the Al-RE Alloys
80%
Yoo H.-S. , Kim Y.-H. , Son H.-T.
Archives of Metallurgy and Materials
|
2020
|
tom Vol. 65, iss. 3
1029--1033
EN
In this study, we investigated the effect of Fe addition (0, 0.25, 0.50 and 0.75 wt.%) on the microstructure, mechanical properties and electrical conductivity of as-cast and as-extruded Al-RE alloys. As the Fe element increased by 0 and 0.75wt.%, the phase fraction increased to 5.05, 5.76, 7.14 and 7.38 %. The increased intermetallic compound increased the driving force for recrystallization and grain refinement. The electrical conductivity of Al-1.0 wt.%RE alloy with Fe addition decreased to 60.29, 60.15, 59.58 and 59.13 % IACS. With an increase in the Fe content from 0 to 0.75 wt.% the ultimate tensile strength (UTS) of the alloy increased from 74.3 to 77.5 MPa. As the mechanical properties increase compared to the reduction of the electrical conductivity due to Fe element addition, it is considered to be suitable for fields requiring high electrical conductivity and strength.
3
Content available Densification and Magnetic Properties of Fe Powder Compacts According to Heat-Treatment Conditions
80%
Yoo H.-S. , Kim Y.-H. , Kim C.-W. , Son H.-T.
Archives of Metallurgy and Materials
|
2023
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tom Vol. 68, iss. 1
47--50
EN
In this study, the effects of heat-treatment conditions of Fe powder compacts on densification, microstructure, strength and magnetic properties were investigated. The prepared Fe powder was compressed in a mold of diameter 20 mm at a pressure of 800 MPa for 30 sec. This Fe powder compact was heat-treated under different atmospheres (air and 90% Ar + 10% H2 and heat-treatment temperatures (300 and 700℃). The Fe powder compacts heat-treated in an Ar+H2 mixed gas atmosphere showed a denser microstructure and higher density than the Fe powder compacts heat-treated in an air atmosphere. Oxygen content in the heat-treatment conditions played a significant role in the improvement of the densification and magnetic properties.
4
Content available Study on Improvement of Surface Properties of Low Carbon Steel Using Laser Cladding
70%
Kim C.-W. , Yoo H.-S. , Jeon J.-Y. , Cho K.-T. , Choi S.-W.
Archives of Metallurgy and Materials
|
2021
|
tom Vol. 66, iss. 4
1033--1036
EN
Laser cladding is a method that can be applied to repair the crack and break on the mold and die surfaces, as well as generate new attributes on the surface to improve toughness, hardness, and corrosion resistance. It is used to extend the life of the mold. It also has the advantages of superior bonding strength and precision coating on a local area compared with the conventional thermal spraying technology. In this study, we investigated the effect of cladding on low carbon alloy steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), which showed high hardness on the die surface. The process conditions were performed in an argon atmosphere using a diode laser source specialized for 900-1070 nm, and the output conditions were 5, 6, and 10 kW, respectively. After the cladding was completed, the surface coating layer’s shape, the hardness according to the cross-section’s thickness, and the microstructure were analyzed.
5
Content available Study of Extrusion Temperature on Extrudability of Al-Zn-Cu Based Alloy
70%
Kim Y.-H. , Yoo H.-S. , Lee K.-S. , Lee S.-H. , Son H.-T.
Archives of Metallurgy and Materials
|
2020
|
tom Vol. 65, iss. 4
1307--1310
EN
In this study, the extrusion characteristics of Al-2Zn-1Cu-0.5Mg-0.5RE alloys at 450, 500, and 550°C were investigated for the high formability of aluminum alloys. The melt was maintained at 720°C for 20 minutes, then poured into the mold at 200°C and hot-extruded with a 12 mm thickness bar at a ratio of 38:1. The average grain size was 175.5, 650.1, and 325.9 μm as the extrusion temperature increased to 450, 500 and 550°C, although the change of the phase fraction was not significant as the extrusion temperature increased. Cube texture increased with the increase of extrusion temperature to 450, 500 and 550°C. As the extrusion temperature increased, the electrical conductivity increased by 47.546, 47.592 and 47.725%IACS, and the tensile strength decreased to 92.6, 87.5, 81.4 MPa. Therefore, the extrusion temperature of Al extrusion specimen was investigated to study microstructure and mechanical properties.
6
Content available Effects of Si Addition on Microstructure and Mechanical Properties of the Al Alloys with High Cr Content Prepared by Gas Atomization and SPS Processes
61%
Kim Y.-H. , Oh I.-H. , Yoo H.-S. , Park H.-K. , Lee J.-H. , Son H.-T.
Archives of Metallurgy and Materials
|
2020
|
tom Vol. 65, iss. 3
1045--1049
EN
This research describes effects of Si addition on microstructure and mechanical properties of the Al-Cr based alloys prepared manufactured using gas atomization and SPS (Spark Plasma Sintering) processes. The Al-Cr-Si bulks with high Cr and Si content were produced successfully using SPS sintering process without crack and obtained fully dense specimens close to nearly 100% T. D. (Theoretical Density). Microstructure of the as-atomized Al-Cr-Si alloys with high contents of Cr and Si was composed multi-phases with hard and thermally stable such as Al13Cr4Si4, AlCrSi, Al8Cr5 and Cr3Si intermetallic compounds. The average hardness values were 703 Hv for S5, 698 Hv for S10 and 824 Hv for S20 alloy. Enhancement of hardness value was resulted from the formation of the multi-intermetallic compound with hard and thermally stable and fine microstructure by the addition of high Cr and Si using rapid solidification and SPS process.
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