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Engineering

Research project: Microstructure and precipitation in Al-V-N microalloyed steels

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High-strength low-alloy structural (HSLA) steels are very important metallic materials with various applications. The aim of this project is to study the microstructures and precipitates in controlled rolled and tempered Al-V-N steels, and the thermodynamic models for estimating the equilibrium compositions of the austenite and carbonitride phases.

Project Overview

The parameters of grain size and precipitates of four as-rolled and tempered microalloyed AI-V-N steels, and their austenite grain growth behaviour have been studied.

The component of particle strengthening for each of the tempered steels has been evaluated by different equations. Estimations of austenite grain size by six different grain growth inhibition models demonstrated that best match to experimental results can be obtained from Gladman and Rios equations and for present AI-V-N steels, it is AIN that controls the austenite grain size. The experimental and calculated results indicated that the drag force of plate-shaped AIN particles probably depends on their orientation and austenitising temperature.

An estimation of the equilibrium compositions of the austenite and carbonitride phases, as well as the mole fraction of each phase in AI-V-N microalloyed steels at different austenitising temperatures was made by calculation based on experimental microalloyed steels from two thermodynamic models, with and without considering aluminium in the steels.

The results indicate that both models produce very similar results and can be used to calculate the equilibrium parameters and predict the solution temperature of carbonitrides and aluminium nitride for an alloy system contained up to three microalloying elements and aluminium. The effect of aluminium on these equilibrium parameters depends on the chemical composition of the steel.

Related research groups

Engineering Materials
(a) Precipitates on dislocations, and (b) Interphase precipitation.
Precipitate morphologies in steel.
with other grain growth inhibition models.
Comparing experimental data
of austenite calculated by two models.
Equilibrium composition

Staff

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