Study on microstructure and bending properties of NbC/Fe cluster-reinforced steel-based laminated composite

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.