학술논문
Mechanical, Electrical, and Microstructural Properties of Combinatorially Sputtered Ni56~92Mo5.9~38W0.5~7.5 alloy films / 조합 합성법을 통해 증착된 Ni56~92Mo5.9~38W0.5~7.5 합금 박막의 기계적, 전기적 및 미세 구조 특성 분석
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
English
Abstract
나노 트윈 (Nano-twin) 구조를 갖는 금속재료는 높은 열 안정성과 뛰어난 기계물성, 그리고 낮은 전기 저항을 가져 주목받고 있다. 그러나, 나노 트윈 구조를 갖는 합금 시스템 내에서도 조성에 따라 물성과 상이 달라져 다양한 조성에서의 합금 물성 분석이 필요하다. Cominatroial synthesis와 High-throughput screening method는 광활한 조성에서의 합금물성을 효율적으로 측정하기에 적합한 방식으로 본 연구에서는 이 방법을 이용하여 nano-twin 구조를 갖는 Ni-Mo-W 합금의 조성과 Microstructure에 의해 변하는 기계적, 전기적 실험 물성을 매핑했다. 실험 결과, as-deposit 상태에서 나노트윈 구조와 비정질 구조가 발견되었으며, 어닐링 후 결정이 유지된 조성, 비정질에서 결정으로 변한 조성, 비정질이 유지된 조성으로 총 3가지 구조로 분류되었다. 이에 따라, 어닐링 전과 후의 Nano-indentation, 4-point probe measurement를 이용하여 기계적, 전기적 물성을 측정하고 TEM(Transmission Electron Microscope)를 이용하여 Microstructure 변화와 물성 변화의 원인을 분석하였다. As-deposit 상태에서는 Nano-twin 구조와 비정질 구조가 물성에 영향을 미쳤으며, Annealing 후에는 Ni-Mo-W 박막 합금의 Magnetic property, Precipitation 및 구조 변화가 영향을 미쳐 물성이 변화하였다. 그리고, Annealing 전 후 물성 측정을 통해 저온에서 물성이 우수한 조성과 열 안정성이 높은 조성을 분석하였다.
Metals and alloys with a nano-twin structure attract attention due to their high thermal stability, improved mechanical properties, and low electrical resistance. However, even within an alloy system having a nano-twin structure, physical properties and phases can differ depending on their compositions. It is, therefore necessary to investigate alloys in various compositions to develop new nano-twin alloys with ideal set of properties. In this study, phases as well as mechanical and electrical properties of Ni56~92Mo5.9~38W0.5~7.5 alloy thin films have been characterized by a combinatorial synthesis and high throughput screening methods. Phase identification with X-ray diffraction and transmission electron microscopy revealed that amorphous structures were formed in the Mo-rich compositions, while nanocrystalline FCC (n-FCC) structures with nano-twins were synthesized for the rest. After annealing the combinatorial specimen at 600 ℃ for 1 hour, three different composition regimes exhibited different phase transition behaviors: from n-FCC to n-FCC (Region Ⅰ), from amorphous to n-FCC (Region Ⅱ), and from amorphous to amorphous (Region Ⅲ) structures. The role of phases and compositions on the mechanical and electrical properties was characterized using nanoindentation and 4-point probe measurements before and after annealing. The compositions with the n-FCC structure (Ni at % < 70, Mo at % > 25~30) showed high hardness of 8.8 ~ 11 GPa and low electrical resistivity of 85 ~ 130 μΩ ∙ cm. The composition range with amorphous structures (Ni at % < 70, Mo at % > 25~30) showed higher hardness (10 ~ 13 GPa) and electrical resistivity of (120 ~ 135 μΩ ∙ cm). After annealing, Regions Ⅰ and Ⅱ had an increased electrical resistivity and hardness, while Region Ⅲ had a reduced electrical resistivity hardness. Mechanisms of the phase formation and transition are suggested and their roles in the physical properties are investigated
Metals and alloys with a nano-twin structure attract attention due to their high thermal stability, improved mechanical properties, and low electrical resistance. However, even within an alloy system having a nano-twin structure, physical properties and phases can differ depending on their compositions. It is, therefore necessary to investigate alloys in various compositions to develop new nano-twin alloys with ideal set of properties. In this study, phases as well as mechanical and electrical properties of Ni56~92Mo5.9~38W0.5~7.5 alloy thin films have been characterized by a combinatorial synthesis and high throughput screening methods. Phase identification with X-ray diffraction and transmission electron microscopy revealed that amorphous structures were formed in the Mo-rich compositions, while nanocrystalline FCC (n-FCC) structures with nano-twins were synthesized for the rest. After annealing the combinatorial specimen at 600 ℃ for 1 hour, three different composition regimes exhibited different phase transition behaviors: from n-FCC to n-FCC (Region Ⅰ), from amorphous to n-FCC (Region Ⅱ), and from amorphous to amorphous (Region Ⅲ) structures. The role of phases and compositions on the mechanical and electrical properties was characterized using nanoindentation and 4-point probe measurements before and after annealing. The compositions with the n-FCC structure (Ni at % < 70, Mo at % > 25~30) showed high hardness of 8.8 ~ 11 GPa and low electrical resistivity of 85 ~ 130 μΩ ∙ cm. The composition range with amorphous structures (Ni at % < 70, Mo at % > 25~30) showed higher hardness (10 ~ 13 GPa) and electrical resistivity of (120 ~ 135 μΩ ∙ cm). After annealing, Regions Ⅰ and Ⅱ had an increased electrical resistivity and hardness, while Region Ⅲ had a reduced electrical resistivity hardness. Mechanisms of the phase formation and transition are suggested and their roles in the physical properties are investigated