Masafumi Noda

Bio: Masafumi Noda is an academic researcher from Chiba University. The author has contributed to research in topics: Superplasticity & Magnesium alloy. The author has an hindex of 4, co-authored 11 publications receiving 76 citations.

Low Temperature Superplasticity and Its Deformation Mechanism in Grain Refinement of Al-Mg Alloy by Multi-Axial Alternative Forging

Abstract: In practical application, an appearance of low temperature superplasticity (LSTP) is one of necessaries conditions. In this paper, to estimate an appearance and deformation mechanisms of this superplasticity, the role of grain boundary sliding (GBS), intragranular deformation and the change of microstructure during superplastic deformation have been investigated for ultrafine-grained Al-Mg alloy with a grain size of less than 1 μm using Multi-Axial Alternative Forging (MAF) technique. In these materials, it shows that the elongation and strain rate sensitivity (m-value) were 340% and 0.39, respectively, at 473 K under a strain rate of 2.8 x 10 -3 s -1 . These results show that superplastic appearance is possible at 473 K. The void formed at 473 K elongated in parallel to the tensile direction, with a length of 15 μm and a width of 5 μm. The intragranular deformation contribution was estimated from the aspect ratio of the grains after deformation and its contribution ratio was about 33.5 %. Therefore, for the appearance of lower temperature superplasticity with large elongation and m-value, the role of intragranular deformation was the most important factor together with GBS under these conditions. As described above, the MAF technique is one of the most effective methods to produce ultrafine-grained material and appearance of lower temperature superplasticity.

Low Temperature Superplasticity and Its Deformation Mechanism in Grain Refinement of Al-Mg Alloy by Multi-Axial Alternative Forging

Abstract: In practical application, an appearance of low temperature superplasticity (LSTP) is one of necessaries conditions. In this paper, to estimate an appearance and deformation mechanisms of this superplasticity, the role of grain boundary sliding (GBS), intragranular deformation and the change of microstructure during superplastic deformation have been investigated for ultrafine-grained Al-Mg alloy with a grain size of less than 1 μm using Multi-Axial Alternative Forging (MAF) technique. In these materials, it shows that the elongation and strain rate sensitivity (m-value) were 340% and 0.39, respectively, at 473 K under a strain rate of 2.8 x 10 -3 s -1 . These results show that superplastic appearance is possible at 473 K. The void formed at 473 K elongated in parallel to the tensile direction, with a length of 15 μm and a width of 5 μm. The intragranular deformation contribution was estimated from the aspect ratio of the grains after deformation and its contribution ratio was about 33.5 %. Therefore, for the appearance of lower temperature superplasticity with large elongation and m-value, the role of intragranular deformation was the most important factor together with GBS under these conditions. As described above, the MAF technique is one of the most effective methods to produce ultrafine-grained material and appearance of lower temperature superplasticity.

Effect of Hydrogenation Treatment on Grain Refinement of Reaction Sintered Ti-6Al-4V Alloy Composites

Abstract: The current study was conducted to develop a Ti-6Al-4V alloy composite material with a fine structure with improved mechanical properties by precipitating TiC particles via reaction-sintering and, additionally, by incorporating the effects of hydrides formed by hydrogenation treatment, using powder to which Mo 2 C had been added. The effects of precipitated TiC particles, and the subsequent generation of hydrides by hydrogenation treatment; heavy-strain working, and recrystallization treatment on grain refinement during the forming process were studied by means of structural observations. Warm rolling and multi-axial alternate forging (MAF) were employed as the heavy-strain working methods. The base metal structure of the Ti-6Al-4V composite material prepared by hydrogenation treatment on the sintered body prepared by spark plasma sintering (SPS) contains particles with a grain size not greater than 1 μm, which become finer with increasing hydrogen content. The particle size of TiC formed by reaction sintering, however, is not changed by heavy-strain working after hydrogenation. Its room temperature tensile strength increases with the amount of TiC precipitation, and is higher than that of non-hydrogenated material.

Effect of Grain Size and Microstructure on Appearance of Low Temperature Superplasticity in Al-Mg Alloy

Abstract: The deformation mechanism and the role of grain boundary sliding (GBS) and intragranular deformation characteristic of low temperature superplasticity (LTSP) were investigated in ultrafine-grained (UFG) Al-Mg alloy using a multi-axial alternative forging technique. In UFG materials, it was shown that elongation and strain rate sensitivity were 340 % and 0.39 respectively at 473 K under a strain rate of 2.8 x 10 -3 s -1 . On the other hand, when grain size exceeded 3 5m, superplasticity did not appear under the same conditions. The main factors affecting the deformation mechanism were investigated based on observations of the microstructure using SEM and TEM. The intragranular deformation contribution, estimated from the aspect ratio of the grains after deformation, was observed to be about 43 %. The appearance of LTSP indicates that the role of intragranular deformation and grain size, together with GBS, were the most important factor.

Friction stir processing technology: A review

Abstract: Friction stir processing (FSP), developed based on the basic principles of friction stir welding (FSW), a solid-state joining process originally developed for aluminum alloys, is an emerging metalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.