Restricted accessResearch articleFirst published online 2025
Effect of microalloying elements Nb and V on phase transformation,microstructure,and strengthening mechanisms in high-strength ferrite-pearlite steels: A comparative analysis
The phase transformation, microstructure, mechanical properties and valence electron structure of 20MnSi steels with different Nb and V contents were investigated by using thermal expansion, micro-tensile, Empirical Electronic Theory (EET) of solids and molecules, among others. The results indicate that the Ar3 (the starting temperature of the transformation from undercooled austenite to ferrite) and the content of proeutectoid ferrite both significantly decrease with the increase of Nb content, while the change with V content is small, which is because the number of covalent electron pairs in C-Nb bonds is higher than that in C-V bonds. The carbonitrides precipitate increase the Ar3 of Nb-V composite steels with the increase of Nb content. In contrast to the decrease in tensile strength/yield strength (Rm/Rel) ratio with increasing V content in V-microalloyed steels, the Rm/Rel ratio in Nb-V composite microalloyed steels increases with increasing Nb content, which is attributed to the precipitation of carbonitrides and the microhardness of pearlite in Nb-V composite microalloyed steels are increased with the increasing Nb content, leading to a greater increment in tensile strength than in yield strength.
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