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Mg-Al 합금의 크리프 거동에 미치는 합금원소의 영향
임현규 ( Hyun Kyu Lim ),김세광 ( Shae K Kim ),김도향 ( Do Hyang Kim ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.1
In this study, three magnesium alloys were investigated; those are 1.5wt.% CaO added AM80, 1.0wt.% CaO added AM60, and conventional MRI153 alloys. Test specimens of three alloys were prepared by re-melting and casting into steel mold with ingots and machining. The mechanical properties and the creep behavior at 150 degrees Celsius of these specimens were determined and their microstructures were characterized using OM and SEM. For the application to die-casting, fluidity test were carried out with spiral mold. Compared with 1.0wt.% CaO added AM60 alloy, 1.5wt.% CaO added AM80 alloy exhibited good creep properties in all test conditions. Moreover, CaO added alloys showed better creep properties than MRI153 alloy at lower load condition. It is proposed that 1.5wt.% CaO added AM80 alloy is useful to apply to power-train parts such as transmission case in vehicles.
0.7wt% CaO 첨가 AZ91D Eco-Mg 다이캐스팅 부품의 미세조직 및 기계적 특성
서정호 ( Jung Ho Seo ),임현규 ( Hyun Kyu Lim ),김세광 ( Shae K. Kim ) 한국주조공학회 2010 한국주조공학회지 Vol.30 No.6
To prevent oxidation of Mg melt, SF6 gas has been generally used for Mg alloys during melting and casting as a cover gas. The use of SF6 gas, however, will be restricted owing to its crucial impact on global warming. Non-SF6 process during melting and casting in diecasting industry has been proved with Eco-Mg alloys by a simple addition of small amount of CaO into Mg alloys. This paper shows non-SF6 diecasting procedures for 0.7wt% CaO added AZ91D Eco-Mg alloys. Cold-chamber diecasting was performed under CO2 atmosphere without SF6 gas. An increment of mechanical properties, especially strength and ductility of Eco-Mg alloys is, in part, due to high-quality melt, refined grain size and Al2Ca second phase strengthening. Microstructures and mechanical properties of 0.7wt% CaO added AZ91D Eco-Mg alloys are evaluated in comparison with those of conventional AZ91D Mg alloy.
반용융 압출시 A7075 합금의 압출 압력 평가 및 Process Window
윤영옥(Young-Ok Yoon),장동인(Dong-In Jang),임현규(Hyun Kyu Lim),김세광(Shae K. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The present study discussed extrudability improvement for 7075 Al wrought alloy by thixoextrusion, with emphasis on controlling thixoextrusion parameters, such as initial ram speed and extrusion temperature of billet in semisolid state. The maximum extrusion pressure for thixoextrusion was greatly decreased than that of conventional hot extrusion. This will contribute to extrudability in terms of extrusion pressure, which in tum means that shorter process time is required and smaller extrusion machine can be applied for the same operation. The elongated grains to extrusion direction were generally observed during conventional hot extrusion, while the thixoextruded microstructures were isotropic.
CaO를 첨가한 ZM21 합금의 기계적 특성 및 생체 부식 특성 평가
양원석 ( Won Seok Yang ),정영길 ( Young Gil Jung ),김세광 ( Shae K Kim ),임현규 ( Hyun Kyu Lim ),김도향 ( Do Hyang Kim ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.11
Mg alloys with unique characteristics, such as high specific strength, low density, high corrosion rate, and so on, are regarded as functional and also structural materials. In particular, Mg alloys have attractive points as metal implants due to their good biocompatibility and biodegradability in the bio- environment and similar elastic modulus to that of bone tissue. The purpose of this work was to investigate the mechanical properties and bio-corrosion properties of extruded Mg-2Zn-1Mn-xCaO (x = 0.5, 1.0, and 1.5) alloys. To evaluate the bio-corrosion properties, electrochemical tests were conducted in Hanks` solution at 37 ℃. The results of tensile and in vitro corrosion tests indicated that the mechanical and biodegradable properties of Mg-2Zn-1Mn-xCaO alloys could be adjusted by controlling the CaO content. (Received September 24, 2013)