Ti-37.5at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ti and Si) were observed for the 5 min mechanically alloyed (MA 5 min) powder, but only phase was observed for the 30 min mechanically alloyed (MA 30 min) powder. phase was observed for the HIPed compact of MA 5 min and 30 min powders at 150 and 190 MPa for 3 hr at . For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at at 190MPa for 3hr. The hardness values of the HIPed compacts at at 150/190 MPa for 3hr were higher than HRC 76. The densification and mechanical property of HIPed compacts was found to depend on more HIP temperature than HIP pressure.

본 실험은 Japanese mint의 생체저장에 있어 저장온도와 필름종류의 영향을 비교하여 적정 저장조건을 제시하고자 실시하였다. 생체중 감소로 볼 때 Japanese mint는 다소 두꺼운 40μm 이상의 필름이 효과적이었다. 저장 중 필름내 가스농도는 필름이 두꺼운 CE 80(ceramic 80μm 필름)이 CE 40(ceramic 80μm 필름)보다 높았으며 저장온도별로는 3℃이하에서는 저온장해가 발생하여 온도별 차이가 없거나 오히려 1℃에서 가장 높은 가스농도를 보였다. 저장 중 엽록소 함량감소는 5%이상의 수분손실과 0.5ppm이상의 에틸렌에 의해 촉진되었으나, 4%이상의 이산화탄소농도에서는 그 감소는 억제되었다. 저장수명은 3℃저장에서 30일로 다른 저장온도의 두배였다. 가장 저장수명이 길었던 3℃에서 저장 최종일에 외관상품질은 CE 40에서 가장 좋았으며 저온장해 정도를 나타내는 이온용출량도 가장 낮게 나타났다. 이상의 결과로 볼 때 Japanese runt 저장시 적정 저장온도는 3℃이며, MA저장시 포장재로는 ceramic 40μm 필름이 적절하였다.

Sintering behavior of nanostructured(NS) W-Cu powders prepared by mechanical alloying (MA) was investigated as a function of sintering temperature. MA NS W-2owt%Cu and W-3owt%Cu composite powders with the crystal size of 20-30 nm were annealed at 90, and thermal characteristics of those powders were investigated by DSC. Sintering behavior of MA NS W-Cu composite powders was investigated during the solid-state sintering and the Cu-liquid phase sintering. The new nanosintering phenonenon of MA W-Cu powders at solid-state sintering temperature was suggested to explain the W-grain growth in the inside of MA powders. The sintering densification of MA NS W-Cu powders was enhanced at Cu melting temperature by arrangement of MA powders, i.e., the first rearrangement of MA powders was occurred, and then the rearrangement of W-grains in the sintered parts was also took place during liquid-phase sintering, i.e., the second rearrangement was happened. Due to the double rearrangement process of MA NS W-Cu powders, the high sintered density with more than 96%o was obtained and the fine and high homogeneous state of W and Cu phases was achieved by sintering at 1200 .

NiAl based ODS (Oxide Dispersion Strengthened) intermetallic alloys have been produced by mechanical alloying (MA) process and consolidated by hot extrusion. Subsequent thermomechanical treatments have been applied to induce secondary recrystallization in an attempt to improve creep resistance in this material. The creep behavior of secondary recrystallized MA NiAl has been investigated and compared with those of as-extruded condition. Minimum creep rate were shown to be approximately two orders of magnitude lower than that in as-extruded condition. The improvement in creep resistance is believed due to the grain coarsening, restricting of dispersoid coarsening as well as increase in grain aspect ratio. Creep threshold stress behavior, below which no measurable creep rate can be detected, has been discussed on the basis of particle-dislocation interaction theory. The threshold stress becomes negligible after secondary recrystallization in MA NiAl, presumably due to dispersoid coarsening and a decrease in grain boundary area during secondary recrystallization.

NiAI기 산화물 분산강화(Oxide Dispersion Strengthende:ODS)합금을 기계적 합금화 (Mechanical Alloying: MA)방법으로 제조하였으며, 열간압축방법으로 성형하였다. 연이어 단순항온처리에 의한 정상결정립성장과 특성조건에서의 thermomechanical treatment 에 의한 이차재결정화를 유도하였다. 결정립 조대화된 ODSD MA NiAI의 creep 성질 및 이에 조대화된 미세조직은 creep 성질이 저하된 반면, 이차재결정화된 MA NiAI의 creep성질은 크게 향상되었다. 이 creep 성질의 향상은 이차재결정화의 특성인 급격한 결정립의 조대화, 분산상의 성장억제 및 grain aspect ratio의 증가에 기인한 것으로 사료되었다. 이차재결정화된 ODS MA NiAI의 creep또는 glide controlled dislocation creep임을 제시하지만, 전체 creep속도가 결정립 크기 및 grain aspect ratio의 영향을 크게 받은 것을 볼 때, 결정립계 미끄럼기구가 주 creep 기구와 조합되어 MA NiAI의 전체 creep기구에 영향을 준 것으로 추정할 수 있었다.

TLP(Transient-Liquid-Phase) bonding of Fe-base MA956 ODS alloy was performed. As insert metal a commercially available Ni-base alloy(MBF50) and an MA956 alloy with additive elements of 7wt% Si and 1wt% B were used. To confirm the idea that a concurrent use of MA956 powder with Insert metals can enhance the homogenization of constituent elements and thereby reduce the thickness of joint interface, MA956 powder was also inserted In a form of sheet. SEM observation and EDS analysis revealed that Cr-rich phase was formed in the bonded interface in initial stage of isothermal solidification during the bonding process, irrespective of kind of insert metals. Measurement of hardeness in the region of bonded interface and EDS analysis showed that a complete homogenization of composition could not be obtained especially in case of MBF50. Joints using either BSi insert metals only or BSi insert together with MA956 powder interlayer showed, however, a remarkable improvement in a compositional homogenization, even though a rapid grain growth in the bonded interface could not be hindered.

Y1Ba2Cu3O7-δ계에서 211상의 성장거동을 관찰하기 위하여 123시편을 1100˚C에서 유지시간을 변화시켜 MgO다결정 기판과 MgO 단결정 기판위에 놓고 소결시킨 후 공냉하였다. 211입자는 유지 시간이 증가함에 따라 성장하였으며MgO단결정 기판보다 MgO다결정 기판을 사용했을때 더 큰 성장을 보였다. CuO양을 변화시키면서 만든 Y2Ba1+xCu3O5+δ 시편에서 211입자는 CuO양이 증가함에 따라 조대해졌으며 0.6mol CuO가 더 첨가된 시편에서 가장 큰 211입자가 관찰되었다. Y2Ba1+xCu3O5+δ시편에서 211입자는 아주 미세하고 균일하게 분포되었다. SnO2첨가로 인한 211입자의 성장억제 효과는 (BaCuO2+ CuO)액상에서보다 CuO액상에서 더 크게 나타났다.

In order to find an optimal friction-welding condition for Ni-base ODS alloy (MA 754) produced by mechanical alloying, joint experiments were performed with various conditions of friction pressures (50~500 MPa), friction times (1~5 sec) and upset pressures (50~600 MPa). The optimal friction pressure and upset pressure must be above 400 MPa and 500 MPa, respectively, which are determined by tensile strengths and fracture features of as-welded joints. A maximum stress설h of 975 MPa could be obtained under these pressure conditions at friction time of 2 sec. Microstructural features of bonded interface by optical microscope and SEM revealed that the interface regions of all specimens are consisted with three distinct regions and defects such as voids, cracks and wavy interfaces exist in the joints produced under not-optimized conditions. EDS results showed that these defects include oxides composed with elements of Al, Y and Ti. The hardness on the bonded interface was higher than in the base metal region. Specimens fractured in bonded interface region had lower strength values compared to those fractured in base metal region. Surfaces of the former showed a typical intergranular fracture.