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Pb 첨가를 통한 Cu계 벌크 비정질 합금에서 in-situ 복합재의 형성에 관한 연구 원문보기
(A) Study on the formation of in-situ composite in Cu-based amorphous alloys by adding Pb

  • 저자

    유대한

  • 학위수여기관

    고려대학교 대학원

  • 학위구분

    국내석사

  • 학과

    신소재공학과

  • 지도교수

  • 발행년도

    2004

  • 총페이지

    ⅳ, 68p.

  • 키워드

    비정질합금 편정합금 응고거동;

  • 언어

    kor

  • 원문 URL

    http://www.riss.kr/link?id=T10074235&outLink=K  

  • 초록

    본 연구에서는 Cu-Pb 상태도가 monotectic 시스템을 갖는다는 것에 착안하여 비정질 형 성능이 우수한 Cu-Ti-Zr-Ni-Sn-Si 비정질 합금에 Pb첨가를 통해 상 분리를 유도하여 비정질 가지 내에 결정상이 분산 된 복합재를 형성하고자 하였다. 고순도의 Cu, Ti, Zr, Ni, Sn, Si 모 합금 원소를 아르곤 분위기 하에서 아크 용해하여 모합금을 제조하였으며, 여기에 Pb를 첨가하여 suction casting법을 이용하여 봉상 형태의 벌크 시편을 제조하였다. 열분석을 통해 시편의 유리쳔이온도(Tg), 결정화 온도(Tx)를 결정하였고 이를 통해서 Trg를 계산하였으며 Pb에 의해 유도된 결정상을 확인하였다. 또한 TEM관찰을 통하여 결정상의 구조를 분석하였다. SEM 분석을 하여 Pb조성과 냉각속도에 따른 미세조직 변화를 관찰하였고, XRD와 EDX분석을 통해 결정상과 그 형상을 일치시켰다. 마지막으로 각 원소별 Mapping을 실시하여 상 분리를 확인하고 상 분리 원칙을 각 원소별 binary mixing enthalpy값으로 설명하였다.


    During the past years, multicomponent bulk metallic glasses (BMGs) have attracted large interest due to their unique properties. So far, several alloy families based on Zr, Pd, Fe, Cu, La, and Mg have been developed, which exhibit very good glass-forming ability and require only low cooling rates of less than 100 K/s to solidify into a glass upon casting into copper molds. BMGs are known to have unique mechanical properties, including high strength, relatively low Young's modulus and perfect elastic behavior. However, they show little global room temperature plasticity, but rather deform by highly localized shear banding. Only a few shear bands are active before failure and consequently, BMGs fail catastrophically exhibiting a stress-strain curve similar to that of a brittle material. The quasi-brittle deformation behavior, which also implies a low toughness, is the primary barrier for the use of BMGs in load-bearing applications. Recent attempts to ductilize BMGs have focused on the preparation of composite materials exhibiting a microstructure consisting of crystalline phases dispersed in the metallic glass matrix. Bulk glassy composites can be obtained by partial devitrification of as-cast metallic glasses, by mechanical alloying of elemental powders blended with insoluble particles, by addition of crystalline particles to the melt prior to casting, by casting a glass-forming liquid around particles/fibers of a second phase, or by precipitating a dendritic metallic phase from the melt during casting. In this study, we intend to induce phase separation by using monotectic system of Cu-Pb to form in-situ composite in Cu-based bulk metallic glass. Multicomponent alloy ingots with composition of (Cu47Ti33Zr11Ni6Sn2Si1)100-x + Pbx(x=0, 1, 2, 3) were prepared by arc melting. From these master alloys cylindrical rods with 3~5mm diameter were produced by suction casting into a copper mold. The thermal analysis, x-ray diffraction, microstructural results are presented for a composite materials exhibiting a microstructure consisting of crystalline phases dispersed in the metallic glass matrix. Finally, the distributions of each components between amorphous matrix and crystalline induced by phase separation resulted from adding Pb are investigated by mapping. The phase separation by monotectic system of Cu-Pb which have very restricted mutual solubility in the solid state could be found to explain this results by using enthalpies of mixing for the binary systems of the elements.


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