Fundamental understanding of Na-induced high temperature embrittlement in Al-Mg alloys

S. Zhang, Q. Han, Zi-kui Liu

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Sodium is an undesirable impurity in aluminium-magnesium alloys. In trace amounts it leads to high temperature embrittlement (HTE), due to intergranular fracture, which results in edge cracking during hot rolling. In the present work, the results of a thermodynamic investigation to elucidate the mechanism are presented. Correlations between HTE, phase formation, temperature and composition in Al-Mg alloys were determined. It is suggested that: (i) HTE is related to the formation of an intergranular Na-rich liquid phase, which significantly weakens the strength of grain boundaries; (ii) for a given Mg content, there exists a maximum Na content above which HTE cannot be avoided; and (iii) for a given alloy, a proper hot-rolling temperature should be chosen with respect to Na and Mg contents to suppress HTE. The HTE sensitive zone and a hot-rolling safe zone of Al-Mg-Na alloys are defined as functions of processing temperature and alloy composition. The tendency of HTE formation was evaluated based on thermodynamic simulations of phase fraction of the intergranular Na-rich liquid phase.

Original languageEnglish (US)
Pages (from-to)147-157
Number of pages11
JournalPhilosophical Magazine
Volume87
Issue number1
DOIs
StatePublished - Jan 1 2007

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embrittlement
liquid phases
thermodynamics
magnesium alloys
aluminum alloys
temperature
tendencies
grain boundaries
sodium
impurities

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

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abstract = "Sodium is an undesirable impurity in aluminium-magnesium alloys. In trace amounts it leads to high temperature embrittlement (HTE), due to intergranular fracture, which results in edge cracking during hot rolling. In the present work, the results of a thermodynamic investigation to elucidate the mechanism are presented. Correlations between HTE, phase formation, temperature and composition in Al-Mg alloys were determined. It is suggested that: (i) HTE is related to the formation of an intergranular Na-rich liquid phase, which significantly weakens the strength of grain boundaries; (ii) for a given Mg content, there exists a maximum Na content above which HTE cannot be avoided; and (iii) for a given alloy, a proper hot-rolling temperature should be chosen with respect to Na and Mg contents to suppress HTE. The HTE sensitive zone and a hot-rolling safe zone of Al-Mg-Na alloys are defined as functions of processing temperature and alloy composition. The tendency of HTE formation was evaluated based on thermodynamic simulations of phase fraction of the intergranular Na-rich liquid phase.",
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Fundamental understanding of Na-induced high temperature embrittlement in Al-Mg alloys. / Zhang, S.; Han, Q.; Liu, Zi-kui.

In: Philosophical Magazine, Vol. 87, No. 1, 01.01.2007, p. 147-157.

Research output: Contribution to journalArticle

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