Strengthening Mechanisms for Ti-and Nb-Ti-micro-alloyed High-strength Steels

摘要

The strengthening mechanisms of hot-rolled steels micro-alloyed with Ti (ST-TQ500)and Nb-Ti (NT-TQ500)were investigated by examining the microstructures of steels using optical microscope (OM),scanning elec-tron microscope (SEM)and transmission electron microscope (TEM).The results revealed almost no differences in the solute solution strengthening and fine-grained strengthening of the two steels,whereas the contributions of pre-cipitation strengthening and dislocation strengthening were different for ST-TQ500 and NT-TQ500.The measured precipitation strengthening effect of ST-TQ500 was 88 MPa higher than that of NT-TQ500;this difference was pri-marily attributed to the stronger precipitation effect of the Ti-containing nanoscale particles.The dislocation strengthening effect of ST-TQ500 was approximately 80 MPa lower than that of NT-TQ500.This is thought to be related to differences in deformation behavior during the finishing rolling stage;the inhibition of dynamic recrystalli-zation from Nb in NT-TQ500 (Nb-Ti)may lead to higher density of dislocations in the microstructure.