0

Full Content is available to subscribers

Subscribe/Learn More  >

Disappearance of Strengthened Micro Texture of Modified 9Cr-1Mo Steel Caused by Stress-Induced Acceleration of Atomic Diffusion at Elevated Temperatures

[+] Author Affiliations
Yifan Luo, Hideo Miura

Tohoku University, Sendai, Japan

Paper No. IMECE2018-87368, pp. V009T12A055; 6 pages
doi:10.1115/IMECE2018-87368
From:
  • ASME 2018 International Mechanical Engineering Congress and Exposition
  • Volume 9: Mechanics of Solids, Structures, and Fluids
  • Pittsburgh, Pennsylvania, USA, November 9–15, 2018
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-5214-9
  • Copyright © 2018 by ASME

abstract

The change of the lath martensitic structure in the modified 9Cr-1Mo steel was observed in the specimens after the intermittent fatigue and creep tests using EBSD (Electron Back-Scatter Diffraction) analysis. The Kernel Average Misorientation (KAM) value and the image quality (IQ) value obtained from the EBSD analysis were used for the quantitative evaluation of the change in the lath martensitic texture. It was found that the lath martensitic texture started to disappear clearly after 107–108 cycles under the fatigue loading at temperatures higher than 500°C when the amplitude of the applied stress exceeded a critical value. Similar change also appeared in the creep test. The critical value decreased monotonically with the increase of the test temperature. This microstructure change decreased the strength of the alloy drastically.

In order to explicate the dominant factors of the change quantitatively, the changes of the microstructure and the strength of the alloy were continuously measured by applying an intermittent creep test at elevated temperatures. It was found that the effective activation energy of atomic diffusion decreased drastically under the application of mechanical stress at elevated temperatures. The effective diffusion length for the disappearance was about 9 μm, and this value was much larger than the initial pitch of the lath martensitic texture of about 0.5 μm, and smaller than the average size of the initial austenite grains of about 20 μm. Therefore, the stress-induced acceleration of atomic diffusion was attributed to the disappearance of the initially strengthened micro texture. The change of the micro texture caused the drastic decrease in the yielding strength of this alloy. Finally, the prediction equation of the lifetime of the alloy was proposed by considering the stress-induced acceleration of atomic diffusion under the application of mechanical stress at elevated temperatures.

Copyright © 2018 by ASME

Figures

Tables

Interactive Graphics

Video

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In