Microalloyed steel

About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.

A comparative study on hot deformation behaviours of low-carbon and medium-carbon vanadium microalloyed steels

Abstract: Carbon is an essential element in steel, but there are still discrepancies regarding its effect on steel hot deformation behaviours. In this research, isothermal compression tests were carried out for a low-carbon (0.05 C) and a medium-carbon (0.38 C) vanadium microalloyed steel with deformation temperatures of 900−1050 °C and strain rates of 0.01−30 s−1. It was found that carbon causes a softening effect at low strain rates (0.01−1.0 s−1), while a hardening effect at high strain rates (10.0−30 s−1). Through constitutive analysis, the hot deformation activation energy for 0.05 C steel is 305.9 kJ/mol in the whole strain rate range, while for 0.38 C steel, the activation energy is 292.3 kJ/mol in the low strain rate range (0.01−1 s−1) and 475.0 kJ/mol in the high strain rate range (10−30 s−1). It was proposed that the addition of carbon decreases the deformation activation energy at low strain rates (0.01−1 s−1), due to its positive influence on the self-diffusion coefficient of iron, which increases the rates of dislocation climb and recovery. On the other hand, carbon lowers the stacking fault energy of austenite, which could make partial dislocation collapse more difficult than dislocation climb and thus becomes the rate-controlling mechanism for 0.38 C steel at high strain rates (10−30 s−1). This gives rise to the higher activation energy and work hardening rate of 0.38C steel at high strain rates. Comparing the power-dissipation-efficiency maps, two peak domains were found in those of 0.38 C steel, while only one peak domain exists in those of 0.05 C steel.

Modelling microstructure evolution and work hardening in conventional and ultrafine-grained microalloyed steels

Abstract: Aspects of the mechanical behaviour of microalloyed steels characterised by grain refinement due to large plastic deformation are discussed. The studies presented in this chapter are intended to promote understanding of the mechanical behaviour of multiphase and ultrafine-grained materials related to the refinement of the microstructure, particularly taking into account the effects of microalloying. Several levels of grain refinement are identified with respect to changes in the strengthening mechanisms. Experimental results have been used to calibrate constitutive equations describing plastic flow mechanics. These equations have been modified and systematically ordered for ultrafine-grained microalloyed steels. Experimental results supported by multiscale numerical analyses have allowed the development of a rheological model for ultrafine-grained microalloyed steels.