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Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures

Journal Article


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Abstract


  • "Commercial-purity aluminum was processed by equal-channel angular pressing (ECAP) at room temperature (RT-ECAP) and cryogenic temperature (CT-ECAP) with liquid nitrogen cooling between two successive passes. It was found that the RT-ECAPed samples showed equiaxed microstructure after 4 and 8 ECAP passes, while the CT-ECAPed samples displayed slightly elongated microstructure and slightly smaller grain size. Moreover, the CT-ECAPed samples had higher hardness values than the RT-ECAPed samples subjected to the same amount of deformation. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the evolution of vacancy-type defects during the ECAP deformation process. The results showed that three types of defects existed in the ECAPed samples: vacancies associated with dislocations, bulk monovacancies and bulk divacancies. The CT-ECAPed samples had a higher fraction of monovacancies and divacancies. These two types of defects are the major vacancy-type defects that can work as dislocation pinning centers and induce hardening, resulting in higher hardness values in the CT-ECAPed samples. A quantitative relationship between material hardness and the defect concentration and defect diffusion coefficient has been established. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved."

Authors


  •   Su, Lihong
  •   Lu, Cheng
  •   He, Lizi (external author)
  •   Zhang, L C. (external author)
  •   Guagliardo, P (external author)
  •   Tieu, A Kiet.
  •   Samarin, S N. (external author)
  •   Williams, J F. (external author)
  •   Li, Hui Jun.

Publication Date


  • 2012

Citation


  • Su, L., Lu, C., He, L., Zhang, L. C., Guagliardo, P., Tieu, A. K., Samarin, S. N., Williams, J. F. & Li, H. (2012). Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures. Acta Materialia, 60 (10), 4218-4228.

Scopus Eid


  • 2-s2.0-84861138841

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=8022&context=engpapers

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5091

Has Global Citation Frequency


Number Of Pages


  • 10

Start Page


  • 4218

End Page


  • 4228

Volume


  • 60

Issue


  • 10

Place Of Publication


  • United Kingdom

Abstract


  • "Commercial-purity aluminum was processed by equal-channel angular pressing (ECAP) at room temperature (RT-ECAP) and cryogenic temperature (CT-ECAP) with liquid nitrogen cooling between two successive passes. It was found that the RT-ECAPed samples showed equiaxed microstructure after 4 and 8 ECAP passes, while the CT-ECAPed samples displayed slightly elongated microstructure and slightly smaller grain size. Moreover, the CT-ECAPed samples had higher hardness values than the RT-ECAPed samples subjected to the same amount of deformation. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the evolution of vacancy-type defects during the ECAP deformation process. The results showed that three types of defects existed in the ECAPed samples: vacancies associated with dislocations, bulk monovacancies and bulk divacancies. The CT-ECAPed samples had a higher fraction of monovacancies and divacancies. These two types of defects are the major vacancy-type defects that can work as dislocation pinning centers and induce hardening, resulting in higher hardness values in the CT-ECAPed samples. A quantitative relationship between material hardness and the defect concentration and defect diffusion coefficient has been established. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved."

Authors


  •   Su, Lihong
  •   Lu, Cheng
  •   He, Lizi (external author)
  •   Zhang, L C. (external author)
  •   Guagliardo, P (external author)
  •   Tieu, A Kiet.
  •   Samarin, S N. (external author)
  •   Williams, J F. (external author)
  •   Li, Hui Jun.

Publication Date


  • 2012

Citation


  • Su, L., Lu, C., He, L., Zhang, L. C., Guagliardo, P., Tieu, A. K., Samarin, S. N., Williams, J. F. & Li, H. (2012). Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures. Acta Materialia, 60 (10), 4218-4228.

Scopus Eid


  • 2-s2.0-84861138841

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=8022&context=engpapers

Ro Metadata Url


  • http://ro.uow.edu.au/engpapers/5091

Has Global Citation Frequency


Number Of Pages


  • 10

Start Page


  • 4218

End Page


  • 4228

Volume


  • 60

Issue


  • 10

Place Of Publication


  • United Kingdom