The Ductile-Brittle Transition Mechanism of 15MnTi Steel Under Dynamic Loading.

This work studied the ductile-brittle transition process of 15MnTi steel under different dynamic loading conditions. The strength of 15MnTi steel increased with strain rate because dislocation movement and element diffusion were inhibited. The fracture mode was different under different loading speeds. When the loading speed was lower than 0.025 m/s, the fracture mode was complete ductile fracture; when the loading speed was 0.1 –0.4 m/s, the fracture mode was ductile-brittle fracture; and when the loading speed was higher than 0.5 m/s, the fracture mode was a brittle fracture. In the three-point bending test, the dynamic brittle fracture rate of 15MnTi steel decreased with increasing crack tip constraint, and the brittle fracture resistance decreased with increasing loading rate. In the Charpy impact test, the fracture mode of the prefabricated crack specimens was a ductile fracture. In addition, when the loading rate was 0.1 m/s, the toughness characteristics were not obvious. The fracture had tear dimples at loading rates ranging from 1 to 3.5 m/s, showing certain ductile fracture characteristics. There were many dislocations in the matrix, and TiC was distributed in the matrix. Plenty of dislocations accumulated around the particles, which improved the strength by hindering the movement of the dislocations. [ABSTRACT FROM AUTHOR]