The Annealing Twins of Fe-20Mn-4Al-0.3C Austenitic Steels during Symmetric and Asymmetric Hot Rolling

The present work investigates the annealing twins of Fe-20Mn-4Al-0.3C austenitic steels in symmetric hot rolling (SHR) and asymmetric hot rolling (ASHR). The average grain size is 26 (±9.6) μm and 11 (±7.0) μm for the tested steel in SHR and ASHR processes. The density of high angle grain boundary (HAGB) and annealing twin boundary increase with the decrease of grain size. The annealing twin is obviously higher in ASHR than in SHR. The linear relation model between the logarithm of twin boundary density and the logarithm of the grain size is established. The grain boundary migration is continuously generated during recrystallization in SHR process. The coincident site lattice (CSL) boundary proportion increases with local grain boundary continuing bugling and the migration direction of bugling grain boundary constantly changes. The tensile property of the tested steel is improved due to the effective grain refinement and high density of annealing twins caused by the severe strain in the ASHR process. The purpose of high density HAGB for austenitic steels is helpful to an improvement in mechanical properties.

Superior Mechanical Properties and Work-Hardening Ability of Ultrafine-Grained Quenched and Partitioned Steels Processed by a Novel Approach Involving Asymmetric Hot Rolling

An approach is proposed to enhance the mechanical properties and work-hardening (WH) ability of low-alloy steels. Using asymmetric hot rolling (AHR) and subsequent direct quenching (DQ) prior to the quenching and partitioning (Q&P) process, an ultrafine-grained Q&P steel with excellent combination of tensile strength of ~1000 MPa and total elongation of ~35% was obtained, which exhibited high WH exponent at higher strain induced by the higher volume fraction and higher stability of film-like retained austenite located between the martensite laths.

Influence of Asymmetric Hot Rolling on Microstructures of Vessel Steel

The symmetric/asymmetric hot rolling experiments were carried out to investigate the effect of shear deformation on microstructure of vessel steel by using electron back-scattered diffraction (EBSD) and field emission transmission electron microscope. The study shows that gradient distribution grain size through the thickness is formed in asymmetric rolled specimen. The grain size in surface is smaller than the one in center. The grain distribution is homogeneous in symmetric rolled specimen. The grain in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen in the same thickness position. The precipitate particles morphology are random precipitate and interphase precipitate in symmetric and asymmetric rolled specimen. The precipitate particles tend to nucleate and grow in the grain in symmetric rolled specimen. The precipitate particles located in grain boundary are observed in asymmetric rolled specimen.