Elucidation of mechanism of high ductility maintaining high strength by fabricating bimodal microstructure in nanoparticle dispersion strengthened alloy

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K05117
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26030:Composite materials and interfaces-related
• Research Institution: Ehime University
• Principal Investigator: Sakamoto Tatsuaki 愛媛大学, 理工学研究科(工学系), 講師 (80403848)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 高強度・高延性化 / バイモーダル組織 / 粉末冶金 / メカニカルアロイング / 分散強化合金

Outline of Final Research Achievements

By blending pure Al and Al-Al2O3 alloy powders, which was obtained by mechanical alloying of pure Al and Al2O3 powders, with at a volume ratio of 1:1 and sintering, a bimodal microstructure consisting of coarse and fine grains of Al matrix was fabricated to achieve high strength and high ductility. When the powders were simply blended and sintered, the strength-ductility balance was hardly improved, but when they were mixed by mechanical milling before sintering, the strength and ductility both increased. The reason for this was that the mixing by mechanical milling increased the interface between the coarse and the fine grain regions, resulting in the introduction of geometrically necessary dislocations during deformation of the sintered alloy, which increased the work hardening rate. Similar results were obtained for Al-Y2O3 alloy powder.

Free Research Field

金属組織学、金属強度学

Academic Significance and Societal Importance of the Research Achievements

合金の高強度化は延性の低下を伴う。この強度と延性のトレードオフを解決する方法として、粗大粒と微細粒からなるバイモーダル（BM）組織の利用が期待されている。BM組織は単相合金に対しても適用可能であることが特徴であるが、分散強化合金でも研究されている。しかし、組織学的パラメータ（結晶粒径、粗大粒と微細粒の体積分率や分布形態、分散粒子の分布形態など）が最適化されておらず、不明な点が多い。本研究は分散強化合金のBM組織利用による高強度高延性化を目指して、まず粗大粒と微細粒の界面に関する情報を得た点で意義深い。実用化に向けた社会貢献への一歩であり、その他の組織学的パラメータの最適化を今後の課題とする。