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Bimodal SiC 입자강화 AZ91D 마그네슘 복합재료의 유동성 및 기계적 특성 평가
裵徹洪,金世光,金永稷 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.7
The objective of this study was to investigate the influence of bimodal reinforcement on the fluidity and mechanical properties of SiC particle reinforced AZ91D Mg composites. The fraction of bimodal SiC particles was fixed at 20 wt% and the mixing ratios of 5 ㎛ to 50 ㎛ SiC particles were 0:1, 1:2, 1:1, 2:1 and 1:0. The results clearly showed that the fluidity and mechanical properties of the composites with bimodal reinforcement were dependent on mixing ratio. In terms of molten state fabrication and tailored mechanical properties, it was obtained that the proper mixing ratio seems to be 1:2.
Ha, Seong-Ho,Yoon, Young-Ok,Kim, Bong-Hwan,Lim, Hyun-Kyu,Lee, Taeg-Woo,Lim, Sung-Hwan,Kim, Shae K. American Scientific Publishers 2018 Science Of Advanced Materials Vol.10 No.5
<P>Pilling-Bedworth ratio (PBR) of metal/dissimilar metal oxide and metal/mixed metal oxide for Al-Mg alloys containing Al2Ca was experimentally examined. The Al-7.5mass%Mg alloy exhibits a thick oxide layer due to the formation of MgO, primarily during the initial stage of oxidation at 788 K. As oxidation continues, the oxide layer of Al-7.5mass%Mg alloy develops an MgAl2O4-spineI. With the addition of 0.3mass%Al2Ca, the surface of the alloy exhibits a passivation effect. The alloy containing Al2Ca additive displays a combination of CaO, MgO and Al2O3 on its surface, and results in a PBR of similar to 1.</P>
Life Cycle Improvement Assessment of Al and Mg Diecasting Processes
Kim, Shae K.,Kim, Young Jig Trans Tech Publications, Ltd. 2005 Materials science forum Vol.486 No.-
<P>To comply with the growing demand for life cycle environmental effect, life cycle assessment (LCA) was carried out for producing A356 aluminum alloy and AZ91D magnesium alloy diecastings. The main emphasis was placed on the improvement assessment for aluminum and magnesium diecasting processes and the comparison between the two competitive processes. The process evaluated was based on yields of finished parts relative to the metal input. This is important both from the environmental point of view and the commercial point of view because the environmental data are sensitive to the design of cast parts and the efficiency of the diecasting operation.</P>
High Cycle Fatigue Behavior of Eco7075-T73 Aluminum Alloy
Kim, Gwan Yeung,Kim, Kyu Sik,Kim, Shae K.,Yoon, Young Ok,Cho, Kyu Sang,Lee, Kee Ahn Trans Tech Publications 2013 Advanced materials research Vol.690 No.-
<P>This study examined the microstructures, mechanical and fatigue properties of the recently developed Eco7075 alloy. Eco7075 is made using Eco-Mg (Mg-Al2Ca) in place of the element Mg during the manufacture of alloy 7075, having economically advantageous and superior properties. In the microstructure observation, average grain size was measured to be 5.2 μm. It consisted of Al matrix containing minute amounts of Al2CuMg, MgZn2, and Ca phases and showed microstructures with reduced amounts of Fe-based phases or oxides. Tensile tests exhibited that this alloy had yield strength of 492 MPa, tensile strength of 548 MPa, and elongation of 12.8%, which showed higher strengths than the conventional 7075 alloy but the similar elongation. Fatigue properties improved significantly compared to those of conventional 7075 alloys (Eco7075: fatigue limit of 330MPa). The superior tensile and fatigue properties of Eco7075-T73 alloy were mainly attributed to grain size refinement, homogeneous distribution of main strengthening phases, and reduced harmful phases of Fe-based intermetallic and oxide.</P>
Effect of Plane Strain on the Microstructure and Texture of AZ31 Sheet with Various Reduction Ratios
Kim, Dae Guen,Kim, Hak Young,Yoon, Young Ok,Kim, Shae K.,Lim, Hyun Kyu Trans Tech Publications, Ltd. 2014 Materials science forum Vol.783 No.-
<P>In this study, the effect of plane strain on the microstructure and texture of AZ31 sheet was investigated with various reduction ratios. To achieve plane strain, that is, to prevent shear deformation during warm-rolling, AZ31 sheet was capsuled by pure Cu tube. The large strain induced by simple one-pass warm-rolling led to the significant grain refinement and texture randomization. The two-dimensional finite-element method showed that the warm-rolling of AZ31 sheet capsuled by Cu tube imposed a uniform plane strain in the whole sheet thickness. The high reduction ratio caused the dynamic recrystallization during annealing of the rolled sheet.</P>
Kim, Bong-Hwan,Ha, Seong-Ho,Yoon, Young-Ok,Lim, Hyun-Kyu,Kim, Shae K.,Kim, Do-Hyang Elsevier 2018 Materials letters Vol.228 No.-
<P><B>Abstract</B></P> <P>This study examined the effect of Ca addition on the selective oxidation of the Al<SUB>3</SUB>Mg<SUB>2</SUB> phase in an Al-5 mass%Mg alloy during oxidation at 400 °C and 500 °C for 72 h. Ca addition led to the formation of the Al<SUB>4</SUB>Ca and Laves_C36 phases besides the primary Al solid solution and Al<SUB>3</SUB>Mg<SUB>2</SUB>. After the oxidation test, there was no significant oxidation in both the Ca-free and Ca-added alloy samples and no visible change in the surfaces between them at 400 °C, which is lower than the melting temperature of Al<SUB>3</SUB>Mg<SUB>2</SUB> (451 °C). At 500 °C, the surface of the Ca-free alloy showed the formation of oxide blisters, which was not observed in the Ca-added alloy. The presence of an Al<SUB>4</SUB>Ca phase at the grain boundaries led to the formation of multi-element oxides containing Al, Mg, and Ca, which can contribute to the formation of a compact oxide layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ca addition in Al-Mg alloy forms two Ca based intermetallic compounds. </LI> <LI> Coexistence of Al<SUB>4</SUB>Ca and Al<SUB>3</SUB>Mg<SUB>2</SUB> phases forms Ca-Mg-Al based oxides after oxidation. </LI> <LI> Ca-Mg-Al based oxides control oxide blister formation from Al<SUB>3</SUB>Mg<SUB>2</SUB> during oxidation. </LI> </UL> </P>