Dilation of an fcc Fe–Cr–Ni alloy by interstitial carbon and nitrogen

Abstract

AbstractAbstractThe volume change arising from introducing interstitial carbon and nitrogen into an fcc Fe–Cr–Ni alloy has been studied. The carbon+nitrogen content varied from 0·3 to 1·3 at.-%. To complement these studies, alloys having a constant low-carbon content and a nitrogen content varying from 0;amp;#x00B7;04 to 0·91 at.-% have also been studied. Volume was determined by X-ray diffraction using electropolished bulk polycrystalline specimens. An atom of carbon or nitrogen was found to increase volume by an amount approximately equal to three times its own volume or 70% of the atomic volume of the iron. In contrast with some studies, it was found that nitrogen exceeds carbon in dilating the fcc iron lattice. This occurs despite the atomic volume of carbon exceeding that of nitrogen. This is ascribed to electronic effects and to carbon–iron bonds stronger than nitrogen–iron bonds. A model calculation is given for the dilation.MST/533