Thermodynamic model and effect of precipitates on hot ductility in low carbon Ti-V bearing microalloyed steel

摘要

A thermodynamic model for Ti-V binary alloy system was established based on two sublattice model to estimate the molar fraction, atom fraction of elements in carbonitrides. Precipitates were analyzed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results showed that The evolution of carbonitrides is (Tio._(98)V_(0.02))(C_(0.06)N_(0.94))→(V_xTi_(1-x))(C_yN_(1-y))→(Ti_(0.55)V_(0.45))(C_(0.23)N_(0.77)), which is consistent with experimental results, in the temperature range from 950°C to 900°C. While, R.A declined rapidly from 70.23% to 43.52% with the size of particles decreasing from 25 to 17nm and quantity increasing 8.4inds/μm~3 to 46inds/μm~2, respectively. In the temperature range from 900°C to 850°C, R.A reduced unobviously from 43.52% to 31.5%. The critical stress, 88.79MPa, was equal to tensile strength at 825°C. Intergranular fracture was easy to occur with higher critical stress below 825°C.