Refinement of Banded Structure via Thermal Cycling and Its Effects on Mechanical Properties of Dual Phase Steel

Abstract

The microstructural refinement by thermal cycling and its effects on the enhancement of mechanical properties and work-hardening response of a typical C-Mn dual phase (DP) steel having the banded ferritic-martensitic morphology is evaluated. It is revealed that the band spacing is reduced by decreasing austenitization temperature and applying thermal cycles to intercritical region, where a saturated spacing will be reached. This results in the enhancement of work-hardening capacity of DP steels as demonstrated based on the instantaneous (incremental) work-hardening rate exponents, modified Crussard-Jaoul analysis, and evaluating the yield ratio after tensile tests. These observations justify the potential of this simple heat treatment route for microstructural control of DP steels. Figure 8. a) Dependence of UTS and total elongation on band spacing and b) Dependence of yield ratio and UTS-YS on band spacing.www.advancedsciencenews.com www.steel-research.de steel research int. 2018, 89, 1700531

Ferrite-to-Austenite and Austenite-to-Martensite Phase Transformations in the Vicinity of a Cementite Particle: A Molecular Dynamics Approach

“…The microstructure development of medium-carbon low-alloy steels containing Cr and Mo under ultrafast heat treatment conditions (rapid heating, peak austenitization followed by quenching) considers the role of undissolved carbides, such as cementite, which influence the austenite formation. Thus, the role of the cementite interface on the microstructure formation in quench-partitioning (QP) and also in ultrafast heating (UFH) steel are under intense discussion [16][17][18][19][20][21][22][23][24][25].…”

The effects of primary thermo-mechanical processing routes and intercritical annealing on the mechanical properties of st37 low carbon steel

“…4b. It has been shown in several recent works that fine-grained DP steels have an exceptional combination of strength and ductility [12,[26][27][28][29][30][31][32][33][34][35]51]. The ferrite grain size of DP1 and DP2 can be estimated as ∼ 8.28 and ∼ 4.85 µ m. The formation of fine-grained DP2 steel is directly related to the initial microstructure before intercritical annealing, i.e., cold-rolled martensitic microstructure.…”

“…Intercritical annealing of cold rolled DP microstructures has been considered by Karmakar et al [30] and Mazaheri et al [31]. Multiple intercritical annealing for microstructural refinement was taken into account by Ghaemifar and Mirzadeh [32,33]. The severe plastic deformation techniques [34] and deformation-induced ferrite transformation [35] have also been used for grain refinement.…”

Cyclic re-austenitization of copper-bearing high-strength low-alloy steels fabricated by laser powder bed fusion

“…This method was first applied by Grange [8] for medium carbon steels. Subsequently, it has been applied to a variety of steels, to achieve grain refinement in order to improve the strength and fatigue properties [4,7,[9][10][11][12][13][14][15][16][17]. The refinement of martensite during cyclic reaustenitization occurs because of the successive transformation between austenite and martensite during the rapid heating and quenching [1].…”