MICROSTRUCTURE, MECHANICAL PROPERTIES AND INTERPHASE PRECIPITATION BEHAVIORS IN V-Ti MICROALLOYED STEEL

Abstract

The microstructure, mechanical properties and precipitation behaviors in a low carbon V-Ti microalloyed steel were investigated using thermal simulation. The microstructural characteristics of tested steel were analyzed using OM and TEM. The results show that the larger volume fraction of ferrite can be obtained for different isothermal temperatures. The ferrite volume fraction is increased and ferrite grain size is reduced as the isothermal temperature is lowered. The planar interphase precipitation can be observed for different isothermal temperatures, and both sheet spacing and precipitates size are refined by lowering isothermal temperature. Moreover, the nanometer-sized carbides have a NaCl-type crystal structure with a lattice parameter of about 0.436 nm and they can obey one variant of Baker-Nutting (B-N) orientation relationship of (100)(carbide)//(100)(ferrite) and [011](carbide)//[001](ferrite). The precipitation hardening for the specimen treated at 680 degrees C for 30 min can reach 360.6 MPa.