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Dual-phase high-entropy alloys for high-temperature structural applications
Lim, Ka Ram,Lee, Kwang Seok,Lee, Jun Seo,Kim, Jin Yeon,Chang, Hye Jung,Na, Young Sang ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.728 No.-
<P><B>Abstract</B></P> <P>The dual-phase AlCoCrFeNi alloy exhibits excellent specific strength in the 773–873 K temperature range. However, the phase transformation taking place above 773 K hinders its structural use at higher temperatures. In the present study, the temperature dependence of the specific strength of the AlCoCrFeNi alloy has been examined from a microstructural point of view. One of the key findings of this work is that the high-temperature phase stability of the dual-phase alloy is strongly affected by its microstructural morphology; this finding provides new insights into the application of high-entropy alloys as high-temperature structural materials, for instance in aerospace engine components.</P> <P><B>Highlights</B></P> <P> <UL> <LI> AlCoCrFeNi alloy exhibits excellent specific strength in 773–873 K temperature range. </LI> <LI> The yield strength of the AlCoCrFeNi alloy exhibits a sharp drop above 773 K. </LI> <LI> The maximum-use temperature can be increased by suppressing the phase transformation. </LI> </UL> </P>
Lim, Ka-Ram,Kim, Won-Tae,Kim, Do-Hyang Korean Society of Microscopy 2012 Applied microscopy Vol.42 No.3
In the present study, the oxidation behavior of $Cu_{50}Zr_{50}$ and $Cu_{46}Zr_{46}Al_8$ metallic glasses has been investigated using transmission electron microscopy with a particular attention on the oxidation behavior in the supercooled liquid state. Identification of the oxidation product after continuous heating treatment shows that in $Cu_{50}Zr_{50}$ metallic glass, $ZrO_2$ with the monoclinic structure forms on the supercooled liquid as well as on the crystallized matrix. On the contrary, in $Cu_{46}Zr_{46}Al_8$ metallic glass, $ZrO_2$ with the tetragonal structure forms on the supercooled liquid, but that with the monoclinic structure forms on the crystallized matrix. The result indicates that the $Cu_{50}Zr_{50}$ metallic glass exhibits far better oxidation resistance in the supercooled liquid state than the $Cu_{46}Zr_{46}Al_8$ metallic glass.
Lim, Ka Ram,Kwon, Heoun Jun,Kang, Joo-Hee,Won, Jong Woo,Na, Young Sang Elsevier 2020 Materials science & engineering. properties, micro Vol.771 No.-
<P><B>Abstract</B></P> <P>A duplex alloy structure is advantageous for overcoming the strength–ductility trade-off dilemma. In this paper, we introduce a novel duplex Al<SUB>12.9</SUB>Co<SUB>20.9</SUB>Cr<SUB>27.3</SUB>Fe<SUB>23.9</SUB>Ni<SUB>14.9</SUB> high-entropy alloy (HEA) reinforced with body-centered-cubic ordered-phase (B2) particles. The hierarchical duplex structure results in an excellent tensile strength of 1031 MPa and acceptable tensile ductility, and the alloy outperforms its conventional counterparts. The yield strength of the alloy is much higher than those of transformation-induced-plasticity strengthened and eutectic duplex HEAs, because it is based on the body-centered-cubic disordered-phase (BCC) matrix. The findings of the present study provide novel guidance for the development of multi-phase HEAs.</P>
유자괸리 업무 효율성 향상을 위한 BIM기반 유지관리 시설물 객체 라이브러리 구축 개발의 필요성
김가람 ( Ka Ram Kim ),임철우 ( Chul Woo Lim ),유정호 ( Jung Ho Yu ) 한국건축시공학회 2010 한국건축시공학회 학술발표대회 논문집 Vol.10 No.1
Recently, the construction industry has been changed more highly and complicacy. According to this, several informational systems of maintenance are introduced suitable the work and the purpose of each maintenance. However there are some problems in the manage the information of maintenance management by without the standization and systematic management of variable information from building life-cycle. This paper purposed the process of creation or management of information which is used for present maintenance through IFC-based facilities object library development is suggested for work efficiency of maintenance management. In addition, it can minimize the reproduce the same information unnecessarily. Fainally, it makes information compatibility through the building life-cycle highly by define the IFC-based object information and standardize the format of information.
Kang, Minju,Lim, Ka Ram,Won, Jong Woo,Na, Young Sang Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-
<P><B>Abstract</B></P> <P>The effect of entropy on the strengths of the disordered and ordered phases was investigated. Cost effective AlCo<SUB>x</SUB>CrFeNi (x = 0, 0.25, 0.5, 0.75, and 1) high-entropy alloys were fabricated reducing Co content. The strength was considerably reduced when the Co content was zero. This was attributed to the low hardness of the A2 phase due to reduced configurational entropy compared with quinary system. On the other hand, the ordered B2 phase showed the opposite tendency. This result shows that the configurational entropy causes opposing effects on disordered and ordered phases, and the importance of considering the effect of entropy on each phase when the number of elements changed, and an alloy is composed of two or more phases, in particular, having BCC structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of Entropy on the mechanical properties of each phase was studied. </LI> <LI> Considerably lower YS of the AlCrFeNi HEA is due to the low strength of the A2 matrix. </LI> <LI> Configurational entropy causes opposing effects on disordered and ordered phases. </LI> </UL> </P>
( Minah Kim ),( Ka Rham Kim ),( Bo Ram Lee ),( Seong Hoon Yoon ),( Hee Jung Ban ),( Yong Soo Kwon ),( In Jae Oh ),( Kyu Sik Kim ),( Yu Il Kim ),( Sung Chul Lim ),( Young Chul Kim ) 대한내과학회 2014 대한내과학회 추계학술발표논문집 Vol.2014 No.1
Background: Expanding of public-private mix(PPM) projects, this study aimed to evaluate the effectiveness of PPM projects. Methods: Expanding of public-private mix(PPM) projects, this study aimed to evaluate the effectiveness of PPM projects. Results: The success rate of treatment of tuberculosis in the pre-PPM group was 39.1% whereas that of the post-PPM group was 66%, showing a significant difference( p<0.001). Conclusions: PPM project improved success rate of treatment of TB by increasing the implementation of drug sensitivity test and decreasing the rate of lost to follow-up. Thus, the need for PPM project should be recognized and the expansion and supplementation of PPM project will be needed.