Precipitation strengthening in titanium microalloyed high-strength steel plates with new generation-thermomechanical controlled processing (NG-TMCP)

• Published in: Journal of alloys and compounds Vol. 689; pp. 542 - 553
• Main Authors: Li, X.-L., Lei, C.-S., Deng, X.-T., Wang, Z.-D., Yu, Y.-G., Wang, G.-D., Misra, R.D.K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.12.2016
• Subjects: High resolution transmission electron microscopy; High strength low alloy (HSLA); Microstructure; Nanoparticles; Thermomechanical controlled processing (TMCP); Nanoparticles; High strength low alloy (HSLA); Thermomechanical controlled processing (TMCP); High resolution transmission electron microscopy; Microstructure
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.08.010

We elucidate here the strengthening mechanisms in titanium microalloyed low-carbon steels, which were rolled into plates of 12 mm thickness using a combination of thermomechanical controlled processing (TMCP) and ultrafast cooling (UFC). The ultrafast cooling combined with thermomechanical controlled processing is referred by us as new generation (NG)-TMCP. Chemical phase analysis, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (TEM) were used to study the characteristics of nanoscale cementite precipitates and microalloyed precipitates. Besides nanoscale TiC, cementite precipitates of size less than ∼35 nm with high volume fraction were observed in Ti-microalloyed steel. Cementite with high volume fraction had a stronger precipitation strengthening effect than nanometer-sized TiC. The precipitation strengthening contribution of nanoscale precipitates of different types and size was estimated together with solid solution strengthening and grain refinement strengthening contribution. The estimated yield strength was consistent with the experimental value. TEM micrograph of (a) interphase TiC, (b) random TiC, (c) Fe3C, (d) HRTEM image, (e) corresponding FFT diffractogram, and (f) IFFT lattice image interphase TiC. [Display omitted] •A good combination of strength and toughness can be obtained controlled by NG-TMCP.•Nanoscale cementite was observed in Ti-microalloyed steel except for TiC.•The contribution of precipitates to yield strength can be greater than ∼300 MPa.