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Nature23/30 December 2004

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Breaking news: Bismuth acts big

Sudden brittle failure of normally ductile metals is a well known phenomenon and a significant cause of concern for engineers. It has been known since 1874 that copper becomes brittle on addition of bismuth. When concentrations of less than 100 parts per million are added, bismuth segregates to grain boundaries, where the failures occur. An electronic origin has been suggested for this impurity-induced embrittlement, but new quantum mechanical calculations point to an atomic size effect as the cause. Large bismuth atoms simply push the copper atoms apart at grain boundaries, weakening the interatomic bonding and imparting brittle fracture behaviour.

letters to nature
Bismuth embrittlement of copper is an atomic size effect
RAINER SCHWEINFEST, ANTHONY T. PAXTON & MICHAEL W. FINNIS
Nature 432, 1008–1011 (2004); doi:10.1038/nature03198
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23/30 December 2004 table of contents

  
  © 2004 Nature Publishing Group