Obtaining Ultrafine and Nanocrystalline Structure by Hot and Warm Deformation in Microalloyed Steel X90

Abstract

In this paper we have investigated the possibility of increasing the complex mechanical properties of steel strength category X90 by refinement the structure of hot and warm deformation. Were carried out tests to determine the critical points of recrystallization and built thermokinetic curves of austenite decomposition. After that, for produce disperse ferrite in samples has been applied to the processing mode, which is exactly the same mode of controlled rolling, then, to obtain nanoscale state of the metal deformed at temperatures of bainite transformation with varying degrees of deformation at different temperatures. It was shown that the dispersion and morphology of the structure and, consequently, the mechanical properties vary depending on temperature and strain, and samples show satisfactory ductility at high strength.

Intensive multi-axis hot deformation of low carbon steel on the MAXStrain II device

“…The MAXStrain unit has been used, for example, to investigate the controlled microstructure evolution, or to investigate the possibility of grain refinement in Al [5,6], Mg [7] and Ti [4,8] based alloys and also in the case of intermetallic alloys [9]. This technique has also been used to investigate of the grain refinement possibilities of microalloyed steels [3,[10][11][12][13]. Although the MAXStrain unit has the potential to be also used for physical simulations of hot forming processes of steels (e.g.…”

“…Although the MAXStrain unit has the potential to be also used for physical simulations of hot forming processes of steels (e.g. continuous rolling of bars or wires), only a minimum of works dealing with this issue or verification of the possibilities of refinement of the final grain of steels after their cumulative hot deformation can be found in the literature [12,13]. It is well known that grain refinement leads to an increase in the mechanical properties of the materials under investigation, and this relationship can be expressed, for example, by the Hall-Petch relation [5,14].…”

Flow Curve Evolution During Cyclic Processing of Ultrafine‐Grained Aluminum Alloy by Multiaxial Forging

“…[4][5][6] One of the earliest cyclic SPD process is multiaxial forging. [11] Using this technique, the microstructure is continuously refined from a coarse to an ultrafinegrained structure. This principle has been used by several technologies, where the geometrical conditions were similar to the open-die forging in the beginning.…”

“…In this process, the specimen is cyclically compressed in two mutually orthogonal directions, while the temperature profile of the specimen is controlled by thermocouple wires in a direct resistance heating system. [11] Using this technique, the microstructure is continuously refined from a coarse to an ultrafinegrained structure. The refinement of the microstructure is induced by the strain path, and this effect is also indicated in the stress-strain relation, i.e., in the constitutive law.…”