Strengthening of heat resistant martensitic steel by Cu addition

Toshihiro Tsuchiyma, Y. Futamura, S. Takaki

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Abstract

Microstructure and creep deformation behavior were investigated in martensitic 9%Cr-(0-4)%Cu steels, and the strengthening mechanism by Cu was discussed in terms of microstructural change during creep deformation. As-quenched specimens have typical lath-martensitic structure. Cu addition gives no influence on the morphology of martensite-laths, but austenite grains tend to be refined with increasing the Cu content. As a result of creep testing for the quenched specimens with a same grain size, it was found that minimum creep rate is greatly lowered and rupture time are prolonged with increasing the Cu content. TEM observations of a creep-deformed 9%Cr-4%Cu steel revealed that dislocations attractively interact with ε-Cu particles within laths, and also lath boundaries are pinned by the ε-Cu particles. Through these interactions between dislocations or lath boundaries and ε-Cu particles, recovery in martensitic structure is greatly retarded, and dislocation density is kept higher during creep deformation. But once the pinning force by ε-Cu particles falls below the applied stress, the recovery rapidly proceeds and the strain rate is accelerated.

Original languageEnglish
Pages (from-to)411-418
Number of pages8
JournalKey Engineering Materials
Volume171-174
Publication statusPublished - 2000

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All Science Journal Classification (ASJC) codes

  • Chemical Engineering (miscellaneous)
  • Ceramics and Composites

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