次世代金属をアトムでデザインする(Designing Next-Generation Metals, One Atom at a Time)

ad
ad
ad
ad

せん断変形中の金属原子の直接可視化により、電池から軽量化車両まで応用可能 Direct visualization of metal atoms during shear deformation has applications from batteries to lightweight vehicles

2022-11-07 パシフィック・ノースウェスト国立研究所(PNNL)

研究者たちは、せん断変形を受けた金属の原子レベルの変化を直接観察することで、物理的な力が金属に及ぼす影響を調査している。
せん断変形によって金属の形状が変化する際に加えられる力は、その原子の配列も変化させ、強度、成形性、導電性などの金属特性に影響を与える。
研究チームは、せん断変形によって、金属をより強くするナノツイスト構造がどのように作られるかを観察した。銅とニオブの合金を観察したところ、銅とニオブの混合金属相の内部で、せん断変形が異なる原子に作用していることがわかった。これは、せん断変形を利用して特定の特性をもつ合金を製造する方法を示す貴重な知見である。
制御された製造プロセスにおいて、これらの力が金属にどのように影響するかを研究して得られた情報は、金属が同じ物理的な力を受ける場所ならどこでも、そのまま変換して適用することが可能である。

<関連情報>

銅単結晶の曲げ変形に伴う亜粒界形成のその場観察 In-situ observation of deformation twin associated sub-grain boundary formation in copper single crystal under bending

Shuang Li,Lei Li,Ayoub Soulami,Cynthia A. Powell,Suveen Mathaudhu,Arun Devaraj & Chongmin Wang
Materials Research Letters  Published: 14 Apr 2022
DOI:https://doi.org/10.1080/21663831.2022.2057201

Abstract

In this work, we use in-situ TEM in combination with finite elemental analysis to reveal the sub-grain boundary formation during bending of Cu single crystal. The deformation process is featured by dislocations propagation, formation of stacking faults and deformation twins, and subsequent formation of a sub-grain boundary. Finite element analysis of stress distribution indicates the stacking faults and deformation twins are all initiated from the region that corresponds to the maximum shear stress. The formation of the sub-grain boundary is through the intersection between primary and secondary stacking faults/deformation twins.
Real-time observation of the plastic deformation process during the bending of Cu single crystal, reveals the sub-grain boundary formation through the intersection between primary and secondary stacking faults/deformation twins.

ナノツインのアシストによる往復剪断荷重下での低角度粒界の可逆形成 Nanotwin assisted reversible formation of low angle grain boundary upon reciprocating shear load

Shuang Li,Nanjun Chen,Aashish Rohatgi,YulanLi,Cynthia A.Powell,Suveen Mathaudhu,Arun Devaraj,Shenyang Hu,Chongmin Wang
Acta Materialia  Available online:16 March 2022
DOI:https://doi.org/10.1016/j.actamat.2022.117850

Abstract

Severe plastic deformation of metals is known to lead to superior properties that cannot be achieved by any traditional metallurgic process. Origin of the superior properties is perceived to be closely associated with grain refinement, a fundamental process during the severe plastic deformation, which is essentially the formation of new grain boundaries. However, the atomistic mechanism of grain boundary formation remains largely obscure. Here, by using in-situ transmission electron microscopy and molecular dynamic simulation, we reveal, for the first time at atomic level, shear-induced low-angle grain boundary (LAGB) formation processes in Au nanocrystal. We discover the LAGB formation is accomplished through inward propagation of nanotwins accompanied by dislocations gliding on twin boundaries, a nanotwin-mediated dislocation slip mechanism, which shows reversible characteristic under reciprocating shear load and is affected by the nanocrystal microstructure and orientation. Our result unveils unprecedented atomistic insights on shear driven grain refinement towards nanostructure of superior properties.

Cu-Nb合金のせん断誘起組織変化のTEMによるその場観察 In-situ TEM observation of shear induced microstructure evolution in Cu-Nb alloy

ShuangLi,Matthew Olszta,LeiL,Bharat Gwalani,Ayoub Soulami,Cynthia A.Powell,Suveen Mathaudhu,Arun Devaraj,Chongmin Wang
Scripta Materialia Available online:23 August 2021
DOI:https://doi.org/10.1016/j.scriptamat.2021.114214

Image, graphical abstract

Abstract

Phase boundaries in multiphase alloys govern defect interaction and chemical intermixing across different phases during plastic deformation. Dynamic interaction of defects with phase boundaries in multiphase alloys, especially for immiscible alloys, has generated more research interest in recent years. Here, we describe a novel approach for carrying out in-situ TEM shear deformation to directly observe interfacial microstructural evolution of a Cu-Nb alloy. A unique double shear specimen geometry is microfabricated by a focused ion beam technique to apply shear deformation upon push loading inside the TEM. From the real-time observation, we discover that the phase boundary with a zigzag morphology effectively blocks stacking faults nucleated in a Cu grain from slipping into a Nb grain. Meanwhile, the Cu phase bears the most plastic deformation through slip or twinning mechanisms. This work sheds light on understanding the shear deformation and the behavior of phase boundaries in multiphase alloys during shear deformation.

タイトルとURLをコピーしました