Abstract
Introducing fine precipitates is an important way to enhance the properties of transformation-induced plasticity (TRIP) steels. In present work, two V-Ti microalloyed TRIP steels containing aluminum with different content were compared. The average size, size distribution and numbers of vanadium-titanium carbides in samples cold rolled, quenched after being held at 800°C and quenched after intercritical annealing at 800°C and being held at bainitic isothermal transformation temperature of 400°C were investigated by using the technique of carbon extraction replica, twin jet chemical polishing thinning and transmission electron microscopy. The carbides were identified to be (Ti,V)C precipitates in steel A and VC in steel B respectively, precipitated mainly from ferrites grains. The average equivalent radius was 3~6nm. Comparison of the experimental results in A and B steel revealed low carbon diffusion rate caused by aluminum inhibited the coarsening of vanadium-titanium carbides. The experimental results also showed that VC carbides dissolution occurred during the intercritical annealing at 800°C.
Highlights
Transformation-induced plasticity (TRIP) steels exhibit an outstanding combination of high strength and ductility, are considered as good candidates for the third generation advanced high strength steels (AHSS)
A 100kg ingot with the designed composition was produced in a vacuum induction furnace filled with argon and hot rolled to 3 mm and subsequent cold rolled to 1.5 mm
Specimens with dimension of 20×20×1.5 mm were cut and encapsulated. These samples were quenched after being held at 800°C and quenched after intercritical annealing at 800°C and being held at bainitic isothermal transformation temperature of 400 °C
Summary
Transformation-induced plasticity (TRIP) steels exhibit an outstanding combination of high strength and ductility, are considered as good candidates for the third generation advanced high strength steels (AHSS). Introducing fine precipitates by adding alloying elements such as V, Ti, or Nb has been one of the notable alternative approaches to further improve the mechanical properties of these steels. The volume fraction, size, morphology and distribution of precipitates have strong effects on the mechanical properties of steel materials [1]. Studies have shown that precipitation strengthening effect of small carbides can significantly improve the mechanical properties of steel [2,3,4]. Two V–Ti microalloyed TRIP steels containing aluminum with different content were designed and investigated. The effect of different content on the behavior of carbides in microalloyed steels has been studied for years [5,6,7]. The precipitation behavior of vanadium-titanium carbides was investigated
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