抄録
Influence of microstructure on the tensile properties and fracture behaviors of Hadfield steel at high strain rate was studied. Hadfield steels sample with different mean grain size with different existence of carbon (precipitates and/or supersaturated solid solution of carbon) were made by rolling at warm temperature and annealing. The sample with conventional grain size (a few 10μm to 100μm) and a small number of carbide shows ductility with local elongation at high speed tensile deformation at 10^3/s. Additionally, fracture surface changes from brittle manner (at 10^<-3>/s) to dimple pattern (at 10^3/s). On the other hand, the fine grained sample with carbides performs brittle fracture at any strain rate. The tensile test at elevated temperature lower than 300℃ at a quasi-static strain rate (10^<-3>/s) clarifies that the elongation recovers as a similar manner as in the change with strain rate. These tendency was discussed with the consideration of the dynamic strain aging as well as the emission of dislocation from clacks.
