Papers by Author: Eri Miura-Fujiwara

Abstract: The training treatments in the shape memory alloy are known as useful method to improve the shape memory effect. In our previous study, it was shown that the training treatments can also improve both the damping capacity and the hardness of the Fe–Mn alloy. In this study, training effects on damping capacity in solution treated Mn-22.5mass%Cu-5.08mass%Ni-1.96mass%Fe alloy have been investigated. As training treatments, the thermal training (only thermal cycling) and the thermo-mechanical training (thermal cycling with deformation) are carried out. Internal friction was measured at room temperature (R. T.) using a free-decay method. Although training effect cannot be found for the samples trained at higher annealing temperature (600 °C and 700 °C), damping capacity of the alloy is improved by thermal training annealed at 400 °C and 500 °C. The trade-off between the damping capacity and mechanical properties can be overcome by the training at lower temperature.

Abstract: Difference of the phase transformation behavior at deformation-induced layer depending on surface treatment methods was investigated using Fe-33mass%Ni alloy. As specimens, two kinds of specimens were prepared. One specimen has austenite (γ) single structure, and the other specimen consists of both martensite (α’) and γ phases. Using these specimens, shot-peening tests were performed, and then phase transformation behavior induced by the shot-peening was compared with that by sliding wear reported in previous literature. The deformation-induced layer induced by shot-peening has very fine microstructure consisted of both α’ and γ phases. The microstructure in the deformation-induced layer formed by shot-peening becomes similar with increasing duration of shot-peening regardless of initial microstucture. On the other hand, the deformation-induced layer induced by sliding wear is reported to have γ single structure regardless of initial microstructure. This microstructural difference between shot-peening and sliding wear comes from the difference of heat generation during the surface treatment. Therefore, it is concluded that phase transformation behavior in deformation-induced layer depends on surface treatment method.

Abstract: Metal-bonded diamond grinding wheel was fabricated by a centrifugal mixed-powder method. The centrifugal mixed-powder method is a novel and effective casting process to obtain functionally graded material (FGM). At the beginning, we performed fundamental experiments using Al-Si alloy system for the purpose of knowing the migration behavior of mixed-powder under centrifugal force. Al-Si hypereutectic alloyed-powder or mixed-powder of Al and Si particles was placed into the mold, and then Al molten metal was cast under a centrifugal force. Cross sectional microstructure observation and quantitative analysis of Si content were conducted using an electron probe microanalyzer. Amount of Si decreased with receding from a mixed-powder region. Si concentration gradient in the sample fabricated Al-Si powder was smaller than the one fabricated using mixed-powder of Al and Si particles. Subsequently, φ 20 mm Cu/diamond grinding wheel was fabricated by the casting method. Graded diamond distribution was successfully obtained.

Abstract: This study aims at producing porous Ti filled with biodegradable materials for biomedical implants by means of spark plasma sintering method (SPS). To improve bone fixation and to obtain appropriate Young’s modulus as a medical implant material, we applied -tri calcium phosphate (-TCP) to the Ti-based composite. Ti/-TCP powder mixtures were sintered by SPS under applied stress of 45MPa with various temperatures and holding time. Vickers hardness (Hv) of obtained composite increased with increasing the holding time up to 10 min, and saturated hardness was approximately 750 Hv, which is extremely higher than that of bulk Ti. Hardness also increased as sintering temperature increased up to 1473 K. From the results of microstructure observations by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDXS), O- and P- containing Ti surrounded around Ti particle, and O diffused into Ti particle to a certain extent. X-ray diffraction results indicated several kinds of Ti-O and/or Ti-P formed in the specimen. Results indicated that it is the brittle phases formed during sintering that increased the hardness.

Abstract: In this study, grain refinement performance of as-cast Al using machining chip of Al instead of the grain refiner is investigated. At first, the machining chips of pure Al are placed in metallic mold. Then, pure Al melt is inserted into the mold with the machining chips. From the microstructure of the as-cast Al using the machining chips, it is found that this machining chip in mold can induce grain refinement of as-cast Al. The increment of the Al chips enhances the grain refinement of the as-cast Al. Moreover, it is shown that preheating the mold can reduce the pore inside as-cast Al using the machining chips. This grain-refinement effect by the machining chips would come from the enhancement of cooling rate and the role of the nucleation site. Therefore, it is concluded that the machining chips of Al can enhance the grain refinement of as-cast Al.

Abstract: Effects of the transformation temperature on formation behavior of the wear-induced layer in Fe alloys are investigated using Fe-33mass%Ni and Fe-30mass%Ni alloys. Martensitic transformation temperature (Ms)　and reverse transformation temperature (As) of Fe-33mass%Ni alloy are lower than those of Fe-30mass%Ni alloy. Microstructure of the wear-induced layer in Fe-33mass%Ni alloy was single austenite phase (γ) with fine grain. On the other hand, the wear-induced layer in Fe-30mass%Ni alloy consists of martensite (α’) and γ with fine structure. This difference is due to the difference of As between these Fe-Ni alloys. Moreover, the microstructure of the wear-induced layer has no dependence on the distribution of α’ in initial microstructure. From obtained results, it is concluded that the formation of the wear-induced layer in Fe alloys is mainly affected by As.