Yongtai Lee

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti.

Effect of Boron Addition on Microstructure and Property of Low Cost Beta Titanium Alloy

A study on effect of boron addition on microstructure and property of low cost beta Ti-Al-Cr-Fe-B alloys are undertaken in the present. The Ti-Al-Cr-Fe alloys were developed as low cost beta Ti alloys for automotive springs, based on Molybdenum equivalency. Low priced Cr-Fe master alloys were introduced as beta stabilizing alloying elements for lowering cost, and elastic modulus. The boron addition is introduced in to refine the ingot microstructure and thus simplify hot working, which should lead to a cost reduction. On the other hand, the Ti-B compositions are able to restrict beta grain growth during heat treatments. So it can increase strength and microstructural stability. The mechanical tests show that the boron modified alloy has good tensile properties in solution condition. Moreover, the alloy can obtain well-balanced high strength levels with acceptable ductility after modulated aging treatment.

A Study on Microstructures and Hardening Behaviors of Ti-12.1Mo-1Fe Alloy

Ti-Mo-Fe alloy was developed as low cost beta Ti alloys for automotive springs, and designed based on Molybdenum equivalency and Bo-Md molecular orbital method. Low priced Mo-Fe master alloys were introduced as alloying elements for the cost and elastic modulus reduction. A laboratory scale ingot was melted by ISM (Induction Skull Melting). Then, microstructure characterization and hardening behavior of a new designed Ti-12.1Mo-1Fe alloy during solution and aging treatment were investigated in the present study by microscopy, X-ray diffraction and hardness test. The results showed that ω phase played a more important role than a phase in hardening. The hardening due to ω phase can lead to high hardness about 470 Hv. However, the coarse a phase resulted in hardness below 300 Hv. On the other hand, the alloy exhibited fast aging response due to high diffusion rate of Fe element in the Ti matrix.

EFFECTS OF TEMPERATURE AND COMPOSITION ON DYNAMIC DEFORMATION BEHAVIOR OF ZR-BASED AMORPHOUS ALLOYS

Effects of test temperature and alloy composition on dynamic deformation behavior of Zr-based amorphous alloys were investigated in this study. Dynamic compressive tests were conducted in the temperature range from room temperature to 380°C using a compressive Kolsky bar. Dynamic compressive test results indicated that both maximum compressive stress and total strain of the amorphous alloys decreased with increasing test temperature because shear bands could propagate rapidly as the adiabatic heating effect was added at high temperatures. Maximum compressive stress and total strain of the alloy containing ductile β crystalline phases were higher than those of the monolithic amorphous alloys over the tested temperature range because β phases played a role in forming multiple shear bands. The alloys having lower Tg or ductile phases had more excellent dynamic properties than the LM1 alloy.

High Efficiency Welding Technology of Titanium Alloy

1948년 미 듀퐁사에서 처음으로 스폰지 타이타늄을 공업적인 생산하기 시작한 이후 타이타늄 소재는 산화 성 및 환원성 분위기에서 내식성이 우수하고, 특히 -200~ 600°C의 온도범위에서 어떤 공업용 합금보다 비강도(강 도/비중)가 우수하여 항공기 및 군수용 재료로서 많이 사용되어 왔으며, 그 외의 다양한 분야에 적용하기 위해 많은 연구가 진행되어 왔다. 21세기 첨단과학과 복지건강 사회에서 친환경 소재, 에너지의 효율적 활용, 인체친화형 시스템 개발, 성능의 지속성 및 신뢰성 구축 등의 중요성이 대두되면서 타이 타늄 소재에 대한 연구 및 관련 산업이 전 세계적으로 빠르게 성장ᆞ확대되고 있다. 타이타늄 소재는 비강도, 생체적합성, 고온강도 및 열적 특성, 해수내식성 등 많 은 장점들로 인해 사용이 증대되고 있으며, 그 사용 용 도도 기존의 방위산업, 우주항공산업 분야에서 자동차산 업, 스포츠, 의료, 해양산업, 석유화학, 원자력 등 다양한 민수산업 및 레저 산업분야로 확대ᆞ발전되어가고 있다. 항공기, 열교환기 등에서 생체용에 이르기까지 용도가 확대됨에 따라 산업현장에서는 타이타늄의 접합 및 용 접 기술의 중요성이 더욱 증대되고 있다.