Behaviors of C or O in bcc Fe and interactions of C-O and oxygen-carbon-vacancy(O-C-□) are investigated by first principles calculations. Octahedral interstitial site is the most stable position for an O atom in bcc ...Behaviors of C or O in bcc Fe and interactions of C-O and oxygen-carbon-vacancy(O-C-□) are investigated by first principles calculations. Octahedral interstitial site is the most stable position for an O atom in bcc Fe. The migration energy of an O atom in bcc Fe is 0.46 eV. The strength of O-Fe(1 nn) bond(0.32) is slightly greater than that of Fe-Fe metallic bond(0.26). Repulsive interactions of C-C, O-O, and C-O exist in bcc Fe. When the concentration of FIA(FIA refers to C or O) is relatively high, a vacancy can attract four FIAs and form stable FIAs-□ complex.展开更多
The crystallographic texture of γ′-Fe4N in compound layer and its influences on the tribological properties of nitrided steel 38CrMoA1 are investigated in the study.The preferred orientation of（200）γ′is produced...The crystallographic texture of γ′-Fe4N in compound layer and its influences on the tribological properties of nitrided steel 38CrMoA1 are investigated in the study.The preferred orientation of（200）γ′is produced by low-temperature nitriding in atmosphere with low nitrogen-hydrogen ratio and increases with the nitriding time.The preferred orientation of（220）γ′appears after 72 h cyclic nitriding.The orientation relationships（0001）ε,/（101）α′,and[ll0]J/[111]γ′（Ill）γ′/（0001）α′ and[011]γ′//[1210]ε,（200）γ′//（l10）α′,and[011]γ′//[111]α′,as well as（1T03）J（220）γ′,and[0100]J/[110]γ′,are established by first-principles method.The misfit of interatornic distance（δ）,determining the phase transition resistance,is calculated.Accordingly,two reaction pathways during nitriding,and α′→γ′and α′→ε→γ′,are assumed,which determines the preferred orientations of γ′-Fe4N.Results of wear tests demonstrate that the specimen with preferred orientation of（200）γ′ exhibits lower frictional coefficient and lower wear rate in comparison with the specimen with（220）γ′ preferred orien-tation.（111）γ′ texture usually relates to the lower frictional coefficient but higher wear rate due to the main slip system parallel to the sliding plane.Therefore,the（200）γ′ preferred orientation has a positive significance in improving the wear properties of steels.展开更多
基金Project supported by the Fundamental Research Funds in Heilongjiang Provincial Universities,China(Grant No.135209204)
文摘Behaviors of C or O in bcc Fe and interactions of C-O and oxygen-carbon-vacancy(O-C-□) are investigated by first principles calculations. Octahedral interstitial site is the most stable position for an O atom in bcc Fe. The migration energy of an O atom in bcc Fe is 0.46 eV. The strength of O-Fe(1 nn) bond(0.32) is slightly greater than that of Fe-Fe metallic bond(0.26). Repulsive interactions of C-C, O-O, and C-O exist in bcc Fe. When the concentration of FIA(FIA refers to C or O) is relatively high, a vacancy can attract four FIAs and form stable FIAs-□ complex.
基金supported by the National Natural Science Foundation of China(Grant Nos.51371070and 51601048)
文摘The crystallographic texture of γ′-Fe4N in compound layer and its influences on the tribological properties of nitrided steel 38CrMoA1 are investigated in the study.The preferred orientation of（200）γ′is produced by low-temperature nitriding in atmosphere with low nitrogen-hydrogen ratio and increases with the nitriding time.The preferred orientation of（220）γ′appears after 72 h cyclic nitriding.The orientation relationships（0001）ε,/（101）α′,and[ll0]J/[111]γ′（Ill）γ′/（0001）α′ and[011]γ′//[1210]ε,（200）γ′//（l10）α′,and[011]γ′//[111]α′,as well as（1T03）J（220）γ′,and[0100]J/[110]γ′,are established by first-principles method.The misfit of interatornic distance（δ）,determining the phase transition resistance,is calculated.Accordingly,two reaction pathways during nitriding,and α′→γ′and α′→ε→γ′,are assumed,which determines the preferred orientations of γ′-Fe4N.Results of wear tests demonstrate that the specimen with preferred orientation of（200）γ′ exhibits lower frictional coefficient and lower wear rate in comparison with the specimen with（220）γ′ preferred orien-tation.（111）γ′ texture usually relates to the lower frictional coefficient but higher wear rate due to the main slip system parallel to the sliding plane.Therefore,the（200）γ′ preferred orientation has a positive significance in improving the wear properties of steels.
