| Popis: |
At present, the research on NbC/Fe cluster-reinforced steel-based composite has been proofread, but little attention has been paid to the effect of Nb/C ratio on composites. The effects of different Nb/C ratio (Nb/C = 1:0.5 and 1:1) on the microstructure and mechanical properties of the composites were studied by in situ hot pressing sintering, and the internal mechanism is explained by the method of first-principles. For Nb/C = 1:0.5, the transition-zone Laves phase Nb2C, NbC/iron-poor zone, and NbC/iron-rich zone were formed on the outside of the Nb particles. When the Nb/C atomic ratio increased to 1:1, the Nb atoms reacted completely to form NbC, and Nb2C was minimized. For Nb/C = 1:1, the deflections of the three- and five-layer composites increased by 112.34 % and 56.79 %, respectively, compared with those of the corresponding layers of T10 steel. The strengthening mechanism of the composite is load transfer, and the toughening mechanism is crack deflection and “delamination cracking”. A first-principles approach showed that the NbC chemical bonds were mainly strong Nb–C covalent bonds, Nb–Nb metallic bonds, and some Nb–C ionic bonds. The chemical bonding of Nb2C comprised Nb–C covalent bonds, strong Nb–Nb metallic bonds, and a large number of Nb–C antibonding states. The advantages of NbC in terms of its thermodynamic and mechanical properties have also been determined. |
