钛含量对 Ti-Mo 钢微观结构及力学性能的影响

：Ti-Mo micro-alloyed steel is widely used in marine engineering，bridge structures，and automotive load-bearing components due to its high strength. Current research on this steel primarily focuses on its strengthening mechanisms，while studies on toughening mechanisms are relatively scarce. In this study，three experimental steels with different Ti contents were selected. After solution treatment，austenitization，and isothermal treatment，the optical microstructure，grain boundary characteristics，distribution of precipitated phases，and mechanical properties of the Ti-Mo micro-alloyed steels were characterized using optical microscopy(OM)，electron backscatter diffraction (EBSD)，transmission electron microscopy(TEM)，tensile testing，and impact testing. The influence of micro⁃ structure on the strength and toughness was analyzed. The results show that as the titanium mass fraction increases from 0. 040% to 0. 157%，the grain size of the experimental steel decreases from 13. 8 μm to 9. 6 μm，and the volume fraction of precipitated phases increases from 0. 022% to 0. 113%. Under the combined effects of grain refinement strengthening and precipitation strengthening，the tensile strength of the steel increases from 513. 3 MPa to 571. 5 MPa. Simultaneously，the proportion of high-angle grain boundaries rises from 73. 6% to 83. 6%，forming a fine and interlocked grain boundary network that effectively hinders crack propagation caused by localized stress concentration. As a result，the impact energy increases from 67. 9 J to 123. 9 J. By optimizing the heat treatment process，the microstructure of Ti-Mo micro-alloyed steel can be tailored to exhibit a combination of acicular ferrite，nanoscale precipi⁃ tated phases，and a high-angle grain boundary network，thereby simultaneously improving both strength and toughness.