Metallurgical Transactions A

, Volume 16, Issue 5, pp 797–805 | Cite as

Embrittlement of austempered nodular irons: Grain boundary phosphorus enrichment resulting from precipitate decomposition

  • R. C. Klug
  • M. B. Hintz
  • K. B. Rundman
Mechanical Behaviour


The microstructures, mechanical properties, and fracture behavior were characterized for a series of Mg treated nodular cast iron specimens austenitized at 1170, 1255, and 1340 K and subsequently austempered at 640 K. The ductility and toughness of the alloy decreased as austenitization temperatures were increased, which is contrary to the behavior anticipated from the observed micro-structural evolution. Fractographic and surface chemical analyses demonstrated that the mechanical property degradation was associated with embrittlement of the austenite grain boundaries by phosphorus. The primary mechanism of grain boundary phosphorus enrichment does not appear to be equilibrium segregation, and an alternative mechanism based on the decomposition of P rich precipitates is proposed and discussed.


Austenite Metallurgical Transaction Nodular Cast Iron Austempering Austenitization Temperature 
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Copyright information

© The Metallurgical Society of American Institute of Mining 1985

Authors and Affiliations

  • R. C. Klug
    • 1
  • M. B. Hintz
    • 2
  • K. B. Rundman
    • 2
  1. 1.Allison Gas Turbines OperationIndianapolis
  2. 2.Department of Metallurgical EngineeringMichigan Technological UniversityHoughton

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