Effect of Ti Addition on the Precipitation Mechanism and Precipitate Size in Nb-Microalloyed Steels

Abstract

The effect of Ti microalloying on the precipitation of NbC particles in Nb-microalloyed and Nb-Ti-microalloyed steels was investigated by scanning transmission electron microscopy. The experimental results illustrate that NbC precipitates tend to be formed via a conventional “nucleation and growth” mechanism in Ti-free steel, while the particles would be precipitated as a complex form of TiN cuboid core and NbC hemispherical cap in Ti-Nb-microalloyed steel with 0.009 wt.% Ti and 0.0046 wt.% N. Ti microalloying contributed to the refinement of the precipitate size, and an enhancement of the volume fraction of NbC particles was also found based on the experimental observations.

Effect of microstructure on tensile properties of quenched and partitioned martensitic stainless steels

“…It has been well known that both NbC and TiC nanocarbides effectively pin grain boundaries thus refining the microstructure during thermo-mechanical processing [28,29]. Indeed, the prior austenite grains in the 420ma alloy are smaller (21.7 μm) compared to those in the 410 and 420 alloys (37.7 μm and 36.2 μm, respectively) (Table 3).…”

“…8). They are typically formed during hot rolling of such steels and characterized by very high thermal stability [28,29]. They have a spherical shape with the average size of 81 ± 26 nm and 43 ± 16 nm, respectively (Fig.…”

Analysis of Recrystallization Kinetics Concerning the Experimental, Computational, and Empirical Evaluation of Critical Temperatures for Static Recrystallization in Nb, Ti, and V Microalloyed Steels

“…Note that, in the precipitation and recrystallization simulation setup, instead of considering the full mixing/demixing of solute atoms Ti, Nb, and V with C and N, the mixing between the substitutional microalloying atoms is assumed to be negligible. This goes along with microanalysis of MX particles, which shows clear separation between Ti-rich, Nb-rich, and V-rich types in comparable steel grades [52][53][54]. Three separate MX compounds, Nb(C,N), Ti(C,N), and V(C,N), are used, accordingly, which was for the benefit of the numerical stability during the thermokinetic simulations.…”