Investigation on the Strengthening and Toughening Mechanism of 500 MPa V-Nb Microalloyed Anti-Seismic Rebars
AbstractTwo types of 500 MPa anti-seismic rebars were produced by V-Nb microalloyed combined with controlled rolling and cooling technology, the strengthening and toughening mechanism of which were investigated. The complex phase microstructures of specimens consist of ferrite, pearlite and bainite (6 – 10 %). Furthermore, a large number of V(C,N) and Nb(C,N) precipitates with size of 5 – 30 nm formed in the ferrite matrix, grain boundaries and on dislocation lines, promoting the precipitation strengthening and inhibiting grain coarsening to controlled cooling microstructure. The mechanical performance of the steels was improved by solution and grain refinement strengthening, precipitation and microstructure strengthening. And the best strengthening effect was obtained by grain refinement, which increased the yield strength more than 35 % strength increment contribution ratio to yield strength. Moreover, about 16.5 % microstructure strengthening increment was obtained due to bainite formation. The plasticity and low-temperature toughness enhancement were mainly attributed to ferrite grain refinement improvement.
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