The precipitation behavior of V（C, N） in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃. The V（C, N） precipitates and its nucleation effect ...The precipitation behavior of V（C, N） in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃. The V（C, N） precipitates and its nucleation effect on ferrite were investigated by TEM and EDS. The experimental results show that there are two remarkable heterogeneous nucleation effects of V（C, N） particles precipitated before γ →/ α phase change： primary reason is that high coherency between V（C, N） and ferrite promotes V（C, N） to become a nucleating center of intragranular ferrite; secondary reason is that the coarsening of V（C, N） causes locally solute-poor region in austenite, thus expedites the nucleation of intragranular ferrites further. Furthermore, the relationship between the size and shape of V（C, N） was studied, and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide.展开更多
MnS, MnS＋V（C, N） complex precipitates in micro-alloyed ultra-fine grained steels were precisely analyzed to investigate the grain refining mechanism. The experimental results shows that MnS, MnS＋V（C, N） precipit...MnS, MnS＋V（C, N） complex precipitates in micro-alloyed ultra-fine grained steels were precisely analyzed to investigate the grain refining mechanism. The experimental results shows that MnS, MnS＋V（C, N） precipitates provide nucleation center for Intra-granular ferrite （IGF）, so that refined grain remarkably. Moreover, substructures such as grain boundary, sub-boundary, distortion band, dislocation and dislocation cell in austenite increased as the deformation energy led by heavy deformation at low temperature （deformation temperature≤800 ℃, deformation quantity≥50%）. As a result, V（C, N） nanophase precipitated at these substructures, which pinned and stabilized substructures. The substructures rotated and transformed into ultra-fine ferrite. 20 nm-50 nm were the best grain size range of V（C, N） as it provided nucleating center for intragranular ferrite. The grain size of V（C, N） were less than 30 nm in the microalloyed steels that with volume ratio of ultra-fine ferrite more than 80% and grain size less than 4 μm.展开更多
基金Funded by the National Natural Science Foundation of China (50775102)the Universities Natural Science Fund Key Project of Jiangsu Province (04KJA430021)
文摘The precipitation behavior of V（C, N） in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃. The V（C, N） precipitates and its nucleation effect on ferrite were investigated by TEM and EDS. The experimental results show that there are two remarkable heterogeneous nucleation effects of V（C, N） particles precipitated before γ →/ α phase change： primary reason is that high coherency between V（C, N） and ferrite promotes V（C, N） to become a nucleating center of intragranular ferrite; secondary reason is that the coarsening of V（C, N） causes locally solute-poor region in austenite, thus expedites the nucleation of intragranular ferrites further. Furthermore, the relationship between the size and shape of V（C, N） was studied, and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide.
基金Funded by the National Natural Science Foundation of China (50475125)the Universities Natural Science Fund Key Project of Jiangsu Province(04KJA430021)
文摘MnS, MnS＋V（C, N） complex precipitates in micro-alloyed ultra-fine grained steels were precisely analyzed to investigate the grain refining mechanism. The experimental results shows that MnS, MnS＋V（C, N） precipitates provide nucleation center for Intra-granular ferrite （IGF）, so that refined grain remarkably. Moreover, substructures such as grain boundary, sub-boundary, distortion band, dislocation and dislocation cell in austenite increased as the deformation energy led by heavy deformation at low temperature （deformation temperature≤800 ℃, deformation quantity≥50%）. As a result, V（C, N） nanophase precipitated at these substructures, which pinned and stabilized substructures. The substructures rotated and transformed into ultra-fine ferrite. 20 nm-50 nm were the best grain size range of V（C, N） as it provided nucleating center for intragranular ferrite. The grain size of V（C, N） were less than 30 nm in the microalloyed steels that with volume ratio of ultra-fine ferrite more than 80% and grain size less than 4 μm.
