The effect of thermomechanical controlled processing on recrystallisation and subsequent deformation-induced ferrite transformation textures in microalloyed steels

Abstract

The evolution of texture components for two experimental 0.06 wt% C steels, one containing 0.03 wt% Nb (Nb steel) and the second containing both 0.03 wt% Nb and 0.02 wt% Ti (Nb-Ti steel), was investigated following a new thermomechanical controlled process route, comprising first deformation, rapid reheat to 1200°C and final deformation to various strains. Typical deformation textures were observed after first deformation for both steels. Following subsequent reheating to 1200°C for various times, the recrystallisation textures consisted primarily of the a-011 h i//RD texture fibre with a weak c-{111}//ND texture fibre, similar to deformation textures, indicative of the dominance of a strain-induced boundary migration mechanism. The texture components after finish deformation were different from the rough deformation textures, with a strong a-011 h i//RD texture fibre at the beginning, and then the strong peaks move to (111) 1 21 and (111) 1 12 textures due to the deformation-induced ferrite (DIF) transformation. The effect of Ti on the recrystallisation textures and deformation textures has also been analysed in this study. The results illustrate that Ti significantly influences the c-{111}//ND texture fibre. Finally, the textures after deformation and recrystallisation in the austenite were calculated based on the K-S orientation relationship between the austenite and ferrite. This allowed the understanding of the mechanism of recrystallisation between first and final deformation and the DIF textures during phase transformation.

Effect of Microstructure and Texture on Mechanical Properties of Resistance Spot Welded High Strength Steel 22MnB5 and 5A06 Aluminium Alloy

“…Compared to the HAZ at the steel side, Figure 10 shows that the steel pseudo-NZs at all the welding parameters had more orientations with more HAGBs resulting in higher hardness [44,45]. This is in accordance with the results obtained by Tutar et al [46] who found that the NZ had higher hardness than the HAZ.…”

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel during Controlled Hot Deformation

“…The first observations of the dynamic transformation were reported in the patent registered in the 1980s [1], who performed large deformations in common C-Mn steels at approximately the Ar 3 temperature and then rapidly quenched, the final microstructure consisted of 70% or more of equiaxed ferrite grains with a size of 4 µm or less. In later works [2][3][4][5][6][7][8], the dynamic transformation was also observed at temperatures above the Ae 3 in plain carbon steels, the combination of large strains and multiple passes conducted to ultrafine grains of ferrite of around 2 µm. Extensive research has been carried out after the pioneering work of Yada and co-workers and numerous papers have been published mainly in the last two decades.…”

“…One of the most polemic topics has been the transformation mechanism of the dynamic ferrite, at least four different approaches [4][5][6][7][8][9][10][11][12][13][14][15] can be found in the literature attempting to explain the transformation path. One of the most accepted interpretations of the transformation mechanisms was proposed by [16], who carried out torsion tests above the Ae 3 temperature at strains from 0.5 to 2 in a steel containing 0.09%C-1.3%Mn-0.02%Si-0.036%Nb.…”

Microstructure Evolution during Controlled Rolling of an Nb–Ti Microalloyed Steel

“…The outstanding properties of high‐strength low‐alloy (HSLA) steels such as high strength besides the suitable ductility and good weldability [ 4,5 ] lead them to be considered as the CT steel alloy. [ 2 ] The improvement in mechanical properties of this kind of steel can be achieved by optimizing processing parameters of different steps in the controlled rolling process, including reheating (soaking time and temperature), [ 6,7 ] rough rolling (reduction and temperature), [ 7–9 ] finish rolling (interpass time, thickness reduction, and temperature), [ 6,10–12 ] cooling (rate), [ 13–18 ] and coiling (temperature), [ 14,19,20 ] to achieve. In other words, to obtain fine‐grained ferrite, it is required to control the microstructural evolution during the thermomechanical treatment.…”

“…[ 25 ] The thermomechanical processing not only influences the microstructure evolutions, but also has a significant impact on the final texture, which makes it the subject of several research works. [ 8,11,26,27 ]…”