Effect of Two Steps Overaging on Mechanical Properties of Tailor Rolled Blank of Dual Phase Steel

Abstract

Herein, a new kind of overaging strategy: two steps of overaging for tailor rolled blank of dual phase steel (DP-TRB) was investigated. The results indicate that two steps of the overaging process is a useful way to control the mechanical properties of DP-TRB. In the premise of satisfying the requirement for the strength of DP590 grade, the total elongation can be significantly increased (3~7% in most cases). Due to the different degrees of ferrite recrystallization (differences of densities of dislocation) among the thicknesses, the obvious changes of mechanical properties among thicknesses are found. The thicknesses zones of 1.0~1.4 mm show lower strength, while the zones of 1.6~1.8 mm present higher strength. Otherwise, the high density of dislocations in samples of 1.6~1.8 mm provide more locations for Cottrell atmospheres, yield plateau occur easier. The zones with different thicknesses for one DP-TRB show two kinds of yield behaviors (continuous yield and non-continuous yield) simultaneously. The subtle C diffusion control by two step overaging leads to the quite different pinning effect of Cottrell atmospheres. Thus, the pinning effect occurs in a gradual way, and a transition state of yield behavior, which combines the characteristic of smooth curve in continuous yield and the plateau in non-continuous yield, is found.

Research on strain aging behavior of ultra-high strength dual-phase steel

“…Then, the strips were quenched by blowing boxes with air subsequently. After cooling, strips were treated in the over-aging furnace to adjust the martensite state and avoid aging problems when using [ 41 ]. The inter-critical annealing time was about 10 min.…”

Microstructural Characteristics and Strengthening Mechanisms of Ferritic–Martensitic Dual-Phase Steels: A Review

“…Accordingly, it cannot be argued with certainty that MM has a great contribution to the strengthening and strengthening corresponding to each of the MM alters, depending on the conditions. Equation (20) indicates that MM strengthening is a function of the martensite shape [42,52]:…”

“…finally, third-generation members are composed of medium manganese (Mn) TRIP steels, quenching and partitioning (Q&P) steels, and carbide-free bainitic (CFB) steels [8]. One of the well-known and outstanding members of AHSSs is DP steel [8,12,[18][19][20]. Although DP steels are placed in the first generation of AHSSs, as shown in Figure 1 [8], extensive research is still being conducted regarding AHSSs [21][22][23][24][25].…”

“…The main microstructural characteristics of these steels are ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM). The range of strength and ductility of DP steels can be extended as compared to other generations of AHSSs via the One of the well-known and outstanding members of AHSSs is DP steel [8,12,[18][19][20]. Although DP steels are placed in the first generation of AHSSs, as shown in Figure 1 [8], extensive research is still being conducted regarding AHSSs [21][22][23][24][25].…”