The effect of annealing temperature on the martensitic transformation behavior, tensile deformation chracteristics and shape recovery etc., has been studied in TiNi based shape memory ribbon fabricated by coldrolling of wire. TiNi based shape memory wire (${\phi}=500{\mu}m$) of which structure is intermetallic compound could be cold-rolled without process annealing up to the reduction rate in thickness of 50%, but a few cracks appear in cold-rolled ribbon in the reduction rate in thickness of 65%. The $B2{\rightarrow}R{\rightarrow}B19^{\prime}$ martensitic transformation or $B2{\rightarrow}B19^{\prime}$ martensitic transformation occurs in annealing conditions dissipating lattice defects introduced by coldrolling. However, in case of higher reduction rate or lower annealing temperature, martensitic transformation in cold-rolled and then annealed ribbons does not occur. The maximum shape recovery rate of cold-rolled ribbons with the reduction rate of 35 and 65% could be achieved at annealing temperatures of 250 and $350^{\circ}C$, respectively. The shape recovery rate seems to be related to the stress level of plateau region on stress-strain curve.

The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

본 연구에서는 다이아몬드의 기계적 화학적 연마(MCP) 에 주목하여 기존에 알려진 다이아몬드 가공연마판을 주물 또는 파우더 소결 방식이 아닌 플라즈마 열분사 기법을 통하여 경제성이 높게 제작하고 이를 상용화 하고자 하였다. 저렴한 주철 모재에 연성이 높고 밀착성이 우수한 Al을 중간 코팅층으로 코팅하고, 상부 코팅층으로 다이아몬드와 화학반응을 하게 되는 Fe-Cr-Ni 및 Ti 코팅층을 플라즈마로 코팅하여 다이아몬드 연마판을 제작하였다. 또한, 물리적인 코팅방법인 플라즈마 열분사 코팅층의 밀착력을 개선 하기 위하여 $550^{\circ}C$ 6시간 동안 열처리를 수행하고 모재와 Al 코팅층 사이에 약 $5{\mu}m$ 정도의 확산층을 형성하여 밀착력을 개선할 수 있었다.

This study was carried out to investigate the relationship between the mechanical properties and damping capacity of thermo-mechanical treated 316L stainless steel. Dislocations, ${\varepsilon}$ and ${\alpha}^{\prime}$-martensites were formed by thermo-mechanical treatment, and the grain size was changed from micrometer to sub-micrometer by 5-cycled thermo-mechanical treatment. The volume fraction of dislocations, ${\varepsilon}$ and ${\alpha}^{\prime}$-martensites was increased, and grain size of austenite increased and lengthened by the with increasing cycle number of thermo-mechanical treatment. In 5-cycled specimens, the volume fraction of ${\alpha}^{\prime}$-martensite was more than 25% and the less than 5% of volume fraction of ${\varepsilon}$-martensite was attained. With increasing number of thermo-mechanical treatment, hardness, strength and damping capacity were increased, but elongation was decreased. Damping capacity was increased with increased hardness and strength, but decreased with increased elongation, and this result was the opposite tendency for general metal.

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.