Stress corrosion in Mg-Al-Mn alloy with residual and concentrated stresses

Shun Ichiro Tanaka, Shuichi Iwata

Research output: Contribution to journalConference articlepeer-review

1 Citation (Scopus)

Abstract

The effects of residual and concentrated stress on a corrosion mode of a thixomolded Mg-Al-Mn alloy (AM-60) in a NaCl aqueous solution were studied in order to elucidate the corrosion mechanism, the time-dependent characteristics of corrosion products and an actual concentrated stress value in a grain (α-Mg) and a grain boundary (Mg17Al12) around an artificial notch. The following results were obtained: (1) Stresses in α-Mg and Mg17Al12 phases existing in a thixomolded Mg alloy plate can be measured separately using the X-ray sin2ψ method in the Cr-Kα irradiation area of 1.0 mm in diameter. The recommended 2θ0 values for stress measurement are 140.0 deg for α-Mg (202) and 133.4 deg for Mg17Al12 (660). (2) The measured residual stresses in a AM-60 plate were about 30 MPa compressive in α-Mg and about 30 MPa tensile in Mg17Al12 phase balancing microscopic region. (3) Even in a lapped Mg-alloy a localized micro-cell exists between α-Mg grain in compressive stress state and grain boundary made of Mg17Al12 in tensile stress state. The proposed model explains well the fact that the grain provides Mg2+ ions for solution whereas grain boundary acts as a nucleation point of the hydrogen gas bubbles. Corrosion in Mg alloy occurs essentially while it is in contact with any aqueous solution. (4) Corrosion mode of AM-60 in 0.9% NaCl aqueous solution was quite different depending on the sort (sign) of the stresses: a fine and dense amorphous hydro-oxide formed in the region of tensile stress whereas a coarse amorphous oxide formed in that of compressive stress. The former reaction product formed in a short time, but the latter grew gradually.

Original languageEnglish
Pages (from-to)755-760
Number of pages6
JournalMaterials Science Forum
Volume404-407
DOIs
Publication statusPublished - 2002 Jan 1
EventProceedings of the 6th European Conference on Residual Stresses - Coimbra, Portugal
Duration: 2002 Jul 102002 Jul 12

Keywords

  • Concentrated Stress
  • Corrosion Mechanism
  • Measured Stress
  • Mg Alloy
  • Micro-Area
  • Residual Stress
  • Stress Corrosion

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint Dive into the research topics of 'Stress corrosion in Mg-Al-Mn alloy with residual and concentrated stresses'. Together they form a unique fingerprint.

Cite this