• 한국안전학회지
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• 제30권4호
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• pp.8-13
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• 2015

The magnetic shape memory alloys have recently received a lot of attention due to the considerable progress achieved in understanding the particular importance and the development of the factors. Among these alloys, the ferromagnetic Co-Ni- alloys have been concerned specially because of the thermoelastic character of the fcc (g) - bct (a) martensitic transformation which exhibits under the action of the temperature (shape memory effect), the stress (superelasticity) and the magnetic field (magnetoelasticity). The morphological, the crystallographical, and the thermal characteristics of thermally induced martensite in Co-35.3Ni-11.3Al(wt.%) and Co-28.1Ni-47.4Fe-3.3Ti (wt.%) alloy have been investigated by the scanning electron microscope (SEM), the X-ray Diffraction (XRD), and the differential scanning calorimeter (DSC).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2003년도 제24회 학술발표회 초록집
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• pp.57-58
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• 2003

• 대한금속재료학회지
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• 제47권12호
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• pp.787-796
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• 2009

The fracture toughness improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile particles was explained by direct observation of microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of ductile particles in the grains after the homogenization treatment at $800{\sim}1100^{\circ}C$. ${\gamma}$ particles were coarsened and distributed homogeneously along {$\beta}$ grain boundaries as well as inside {$\beta}$ grains as the homogenization temperature increased. The in situ microfracture observation results indicated that ${\gamma}$ particles effectively acted as blocking sites of crack propagation, and provided stable crack growth that could be confirmed by the R-curve analysis. This increase in fracture resistance with increasing crack length improved overall fracture properties of the alloys containing ${\gamma}$ particles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.105-107
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• 2003

강자성 형상기억합금은 기존의 압전재료 및 열적 형상기억합금을 이용한 전기-열-기계적 거동의 액츄에이터 재료를 대신할 수 있는 새로운 고성능 액츄에이터 재료로서 각광을 받고 있다. 그러한 강자성 형상기억합금들 중의 한 종류로서 단결정 및 다결정 $Ni_{2}MnGa$ 합금을 이용하여 자장인가시 변형을 관찰하였다. 거대 자장 유기 변형률을 설명하기 위하여 두 모델이 제안되었다. 변태 온도보다 낮은 온도에서는 마르텐사이트 상의 재배열에 의하여 변형이 일어났으며, 그 변태온도보다 높은 온도에서는 상변태에 의한 변형이 일어났다. 미세구조 관찰을 통하여 인가 자장의 방향에 따라 우선적으로 형성되는 마르텐사이트상을 관찰하였다.