Modeling of mechancial prpoerties of metals with ultrafine microstructures

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04066
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Yamagata University
• Principal Investigator: Kuroda Mitsutoshi 山形大学, 大学院理工学研究科, 教授 (70221950)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 金属材料 / 強度 / 粒径 / 強ひずみ加工

Outline of Final Research Achievements

The present study addresses the mechanical behavior of ultra-fine grained metals processed by severe plastic deformation (SPD) and its mathematical modeling. Industrial pure aluminum and copper were used as target materials. The main results are: (1) No augmentation of athermal (permanent) strength by grain refinement attributed to SPD was observed; (2) Grain boundaries produced by SPD might not act as strong barriers to dislocation motion; (3) The phenomenon "hardening by annealing" was observed only for aluminum but not for copper, and thus the strengthening behavior associated with thermal treatment is significantly different depending on the material; (d) A simple material model (elasto-viscoplastic type) that represents the observed material behavior was formulated.

Free Research Field

弾塑性力学，金属材料

Academic Significance and Societal Importance of the Research Achievements

従来，強ひずみ加工によって作製される超微細結晶粒材料は一律に「高強度材料」として認識されてきた．本研究では，その強度を時間に依存しない永久強度（非熱的強度）と時間依存の熱的強度に実験的に分離した上で，改めて結晶粒径の影響を調べた．その結果，加工まま材場合，非熱的強度は一般に認識されるよりも大幅に低く，結晶粒径は非熱的強度にほとんど寄与していないことを見出した．非熱的強度は，環境に左右されない応力保持能力として構造材料の基盤的性能であり，これを広範に調査して，構造部材並びに構造物全体の安全性向上を目指すことの意義は大きい．