초록 ▼

Ⅳ. 연구개발결과
마그네슘 합금 내에 생성되는 Mg₁₇Sr₂ 금속간화합물은 분산상으로 존재할 경우 변형 수용이 가능하였으나, 이를 기지상으로 활용할 경우 연성이 크게 떨어지는 것을 확인하였음.
Mg₁₇Sr₂상 분율을 줄인 Mg-18.7Sr에서 연성을 기존보다 개선할 수 있었으나, 탄성영역에서 파단되어 추가적인 성분계 개선이 필요함. 2원계 금속간화합물 제조 중 DED(direct energy deposition) 공정을 적용하여 Ti-Co, T

Ⅳ. 연구개발결과
마그네슘 합금 내에 생성되는 Mg₁₇Sr₂ 금속간화합물은 분산상으로 존재할 경우 변형 수용이 가능하였으나, 이를 기지상으로 활용할 경우 연성이 크게 떨어지는 것을 확인하였음.
Mg₁₇Sr₂상 분율을 줄인 Mg-18.7Sr에서 연성을 기존보다 개선할 수 있었으나, 탄성영역에서 파단되어 추가적인 성분계 개선이 필요함. 2원계 금속간화합물 제조 중 DED(direct energy deposition) 공정을 적용하여 Ti-Co, Ti-Cu계 소재를 성공적으로 제조할 수 있었고, 이 중 Ti-40Cu에서 상용 TiAl 대비 상온 연성과 강도를 2배 가량 향상시킬 수 있었음. Ti₃Al상을 활용하고자 Ti-25Al-5Nb, Ti-25Al-10Nb 소재를 제조하였으며, 이 중 Ti₃Al상 분율을 높인 Ti-25Al-10Nb에서 상용 TiAl 소재 대비 향상된 고온 강도를 얻을 수 있었음.
당해연도에 수행한 일부 성분계는 본 과제의 정량적 목표를 상회하는 기계적 특성을 나타내었으며, 이 중 Ti계 금속간화합물에 대한 연구 결과 일부를 SCI급 저널에 투고하여 출판하였음. 진도점검 시 기존 소재와의 특성 비교 필요성과 연성 개선 필요성에 대해 지적을 받았고, 이를 반영하여 상온 연성이 개선된 개발 소재의 특성을 AZ91 및 TiAl 등 기존 소재와 비교하여 나타내었음.

(출처 : 요약문 4p)

Abstract ▼

The project entitled "Development of advanced intermetallic-based materials and research on their characteristics“ has been performed to explore various intermetallic-based materials with improved room temperature ductility.

The intermetallic compounds, that combine two or more species of met

The project entitled "Development of advanced intermetallic-based materials and research on their characteristics“ has been performed to explore various intermetallic-based materials with improved room temperature ductility.

The intermetallic compounds, that combine two or more species of metal elements in a simple integer ratio, are known to exhibit extraordinary thermal, physical and mechanical properties that cannot be inferred from the properties of raw materials and commercial materials. A binary combination of metal elements on the periodic table can result in more than 3,000 combinations, but intermetallic compounds that have been researched, developed, and commercialized are limited to a few parts of the combinations such as TiAl, NiTi and etc. Therefore, the major scope in this study is to find new binary or tertiary combinations of metallic elements, which could provide inherently improved room temperature ductility, and to analyze their deformation mechanisms.

At first, the Mg₁₇Sr₂ intermetallic compound, which has been confirmed to be deformable as the precipitates in Mg-Sr alloy, was selected to be used as the matrix phase. A significantly reduced ductility, observed in Mg₁₇Sr₂ single-phase intermetallic compound, leads to the modification of the given system to include the magnesium phase, as in the eutectic composition. The magnesium phase indeed contributed to prolonged tensile elongation, however, further modification is necessary to reach 1% tensile elongation because the fracture occurred in the elastic region even in the Mg-18.7Sr alloy. Second, we inquired into various binary intermetallic compounds in the Mg-Ca, Mg-Y, Mg-Ni, Ti-Fe, Ti-Cr, Ti-Mn, Ti-Co, and Ti-Cu systems. Accordingly, Mg₂Ni-based, TiCo-based, and TiCu-based materials were successfully manufactured via casting and direct energy deposition. Mg-23.5Ni, containing more than 50 vol.% of Mg₂Ni phase, fractured at the end of an elastic region corresponding to 0.67% elongation, whereas Ti-40Cu alloy, composed of TiCu and Ti₂Cu phases, exhibited 1.1GPa and 1.17% of tensile strength and elongation, respectively. The tensile properties of Ti-Cu alloy exceed comparable to commercial TiAl alloy, and thereby further enhancement of elongation through a proper heat treatment can be expected.

Ti-25Al-5Nb and Ti-25Al-10Nb alloys have also been designed to utilize the Ti₃Al intermetallic compound for improved high temperature strength. The Ti-25Al-10Nb alloy could provide higher tensile strength than commercial TiAl at 800℃.

We developed the intermetallic-based materials having more than 0.5% room temperature elongation, as a result, several intermetallic compounds, Mg₂Ni, TiCu, and Ti₃Al, were selected as candidates for intermetallic compounds having room temperature ductility. In the next year, detailed microstructure analyses and deformation mechanisms will be carried out for the selected intermetallic compounds.

(source : SUMMARY 5p)