Transformation induced toughening and flaw tolerance in pure nanocrystalline aluminum

S. Kumar, Md Amanul Haque, Huajian Gao

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Pure bulk metals do not exhibit solid-solid phase transformation since they deform and fail far below the required stress levels for phase transformation, which exceeds hundreds of GPa. We propose that for certain grain size, thickness and notch geometry, classical deformation modes can be suppressed to induce phase transformation in pure metal films at stresses few orders of magnitude lower than the theoretical values. For the first time, we present in situ transmission electron diffraction evidence of face-centered cubic (FCC) to hexagonal ω phase transformation in 99.99% pure nanocrystalline aluminum at room temperature and only 2.5 GPa of tensile stress. For 60 nm average grain size, the aluminum films did not show any appreciable diffusion-based processes such as grain growth, rotation and sliding. At the same time, the 200 nm thick specimens are thin enough for the dislocations to escape through the surface. With no active dislocation sources, in situ microscopy did not show any dislocation-based deformation either. Facilitated by the absence of dislocation and diffusion based processes, the uniaxial nature of specimen loading results in phase transformation at stresses two orders of magnitude lower than that predicted for aluminum. We also propose that phase transformation can result in a flaw tolerance in the material.

Original languageEnglish (US)
Pages (from-to)121-128
Number of pages8
JournalInternational journal of plasticity
Volume44
DOIs
StatePublished - Mar 1 2013

Fingerprint

Toughening
Aluminum
Phase transitions
Defects
Metals
Grain growth
Tensile stress
Electron diffraction
Microscopic examination
Geometry

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

@article{65bd8997148e45d9b89e2529ad423642,
title = "Transformation induced toughening and flaw tolerance in pure nanocrystalline aluminum",
abstract = "Pure bulk metals do not exhibit solid-solid phase transformation since they deform and fail far below the required stress levels for phase transformation, which exceeds hundreds of GPa. We propose that for certain grain size, thickness and notch geometry, classical deformation modes can be suppressed to induce phase transformation in pure metal films at stresses few orders of magnitude lower than the theoretical values. For the first time, we present in situ transmission electron diffraction evidence of face-centered cubic (FCC) to hexagonal ω phase transformation in 99.99{\%} pure nanocrystalline aluminum at room temperature and only 2.5 GPa of tensile stress. For 60 nm average grain size, the aluminum films did not show any appreciable diffusion-based processes such as grain growth, rotation and sliding. At the same time, the 200 nm thick specimens are thin enough for the dislocations to escape through the surface. With no active dislocation sources, in situ microscopy did not show any dislocation-based deformation either. Facilitated by the absence of dislocation and diffusion based processes, the uniaxial nature of specimen loading results in phase transformation at stresses two orders of magnitude lower than that predicted for aluminum. We also propose that phase transformation can result in a flaw tolerance in the material.",
author = "S. Kumar and Haque, {Md Amanul} and Huajian Gao",
year = "2013",
month = "3",
day = "1",
doi = "10.1016/j.ijplas.2012.12.005",
language = "English (US)",
volume = "44",
pages = "121--128",
journal = "International Journal of Plasticity",
issn = "0749-6419",
publisher = "Elsevier Limited",

}

Transformation induced toughening and flaw tolerance in pure nanocrystalline aluminum. / Kumar, S.; Haque, Md Amanul; Gao, Huajian.

In: International journal of plasticity, Vol. 44, 01.03.2013, p. 121-128.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Transformation induced toughening and flaw tolerance in pure nanocrystalline aluminum

AU - Kumar, S.

AU - Haque, Md Amanul

AU - Gao, Huajian

PY - 2013/3/1

Y1 - 2013/3/1

N2 - Pure bulk metals do not exhibit solid-solid phase transformation since they deform and fail far below the required stress levels for phase transformation, which exceeds hundreds of GPa. We propose that for certain grain size, thickness and notch geometry, classical deformation modes can be suppressed to induce phase transformation in pure metal films at stresses few orders of magnitude lower than the theoretical values. For the first time, we present in situ transmission electron diffraction evidence of face-centered cubic (FCC) to hexagonal ω phase transformation in 99.99% pure nanocrystalline aluminum at room temperature and only 2.5 GPa of tensile stress. For 60 nm average grain size, the aluminum films did not show any appreciable diffusion-based processes such as grain growth, rotation and sliding. At the same time, the 200 nm thick specimens are thin enough for the dislocations to escape through the surface. With no active dislocation sources, in situ microscopy did not show any dislocation-based deformation either. Facilitated by the absence of dislocation and diffusion based processes, the uniaxial nature of specimen loading results in phase transformation at stresses two orders of magnitude lower than that predicted for aluminum. We also propose that phase transformation can result in a flaw tolerance in the material.

AB - Pure bulk metals do not exhibit solid-solid phase transformation since they deform and fail far below the required stress levels for phase transformation, which exceeds hundreds of GPa. We propose that for certain grain size, thickness and notch geometry, classical deformation modes can be suppressed to induce phase transformation in pure metal films at stresses few orders of magnitude lower than the theoretical values. For the first time, we present in situ transmission electron diffraction evidence of face-centered cubic (FCC) to hexagonal ω phase transformation in 99.99% pure nanocrystalline aluminum at room temperature and only 2.5 GPa of tensile stress. For 60 nm average grain size, the aluminum films did not show any appreciable diffusion-based processes such as grain growth, rotation and sliding. At the same time, the 200 nm thick specimens are thin enough for the dislocations to escape through the surface. With no active dislocation sources, in situ microscopy did not show any dislocation-based deformation either. Facilitated by the absence of dislocation and diffusion based processes, the uniaxial nature of specimen loading results in phase transformation at stresses two orders of magnitude lower than that predicted for aluminum. We also propose that phase transformation can result in a flaw tolerance in the material.

UR - http://www.scopus.com/inward/record.url?scp=84875214202&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84875214202&partnerID=8YFLogxK

U2 - 10.1016/j.ijplas.2012.12.005

DO - 10.1016/j.ijplas.2012.12.005

M3 - Article

AN - SCOPUS:84875214202

VL - 44

SP - 121

EP - 128

JO - International Journal of Plasticity

JF - International Journal of Plasticity

SN - 0749-6419

ER -