2025年9月29日、Prof. Karsten Durst によるご講演が第176回構材ゼミとして開催されました。
日時：2025年9月29日（月曜日）14:00-15：00
場所：NIMS千現地区 先進構造材料研究棟5階カンファレンスルーム
講演題目：Advanced Nanoindentation testing for studying thermally and electron-beam induced deformation mechanism in alloys and glasses.
講演者：Prof. Karsten Durst, Physical Metallurgy, Technical University Darmstadt, Germany
開催者：Thomas Edward James Edwards (強度物性グループ)
講演後の集合写真
Prof. Karsten Durst（右から4番目）
Abstract:
Thermally activated mechanism play an important role in the plastic deformability of a wide variety of materials, for instance in the brittle to ductile transition of bcc metals, oxide glasses, as well as the superplastic behaviour of nanocrystalline materials. Using a newly developed high temperature nanoindenter and different nanoindentation protocols, it is possible to analyze these mechanisms in a wide range of temperatures (RT to 1100°C) as well as a wide range of strain rate (10-10-7). Furthermore, it has been shown recently that even the electron flux inside the SEM can strongly enable viscous flow mechanism even at room temperature.
In this talk, we will give an overview on the different testing protocols and will show how the so called high temperate scanning indentation method can be used to assess the brittle to ductile transition of Mo and Cr pure metals via an analysis of the activation volume as a function of testing temperature. In a second example, we will show also a brittle to ductile transition for oxide glasses, highlighting that cracking can be effectively suppressed during electron beam irradiation, similar to effects observed during high temperature testing. Finally, the reversible and irreversible softening of an Cu-X nanocrystalline alloy series during high temperature deformation will be assessed via indentation testing as well as uniaxial testing. In a certain temperature regime, the nanocrystalline alloys reversibly soften and have a even lower flow stress compared to their coarse grained counter parts.