Abstract
Ferritic–martensitic dual-phase (DP) steels are prominent and advanced high-strength steels (AHSS) broadly employed in automotive industries. Hence, extensive study is conducted regarding the relationship between the microstructure and mechanical properties of DP steels due to the high importance of DP steels in these industries. In this respect, this paper was aimed at reviewing the microstructural characteristics and strengthening mechanisms of DP steels. This review article represents that the main microstructural characteristics of DP steels include the ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM), which play a key role in the strengthening mechanisms and mechanical properties. In other words, these can act as strengthening factors, which were separately considered in this paper. Thus, the properties of DP steels are intensely governed by focusing on these characteristics (i.e., FGS, MVF, and MM). This review article addressed the improvement techniques of strengthening mechanisms and the effects of hardening factors on mechanical properties. The relevant techniques were also made up of several processing routes, e.g., thermal cycling, cold rolling, hot rolling, etc., that could make a great strength–ductility balance. Lastly, this review paper could provide substantial assistance to researchers and automotive engineers for DP steel manufacturing with excellent properties. Hence, researchers and automotive engineers are also able to design automobiles using DP steels that possess the lowest fuel consumption and prevent accidents that result from premature mechanical failures.
Highlights
Introduction published maps and institutional affilNowadays, famous steels referred to as advanced high-strength steel (AHSS) are highly regarded [1,2,3,4,5,6,7]
The members of the first generation are composed of dual-phase (DP) steels, complex phase (CP) steels, transformation-induced plasticity (TRIP) steels, and martensitic (MART) steels, while second-generation members are composed of austenitic stainless steels, lightweight steels with induced plasticity (L-IP), and twinning-induced plasticity (TWIP) steels, and third-generation members are composed of medium manganese (Mn) TRIP steels, quenching and partitioning (Q&P) steels, and carbide-free bainitic (CFB) steels [8]
Increasing the rolling reduction increases the nucleation sites of austenite, resulting in an increasing martensite volume fraction (MVF) [53]. (II) Hot rolling of a ferritic–pearlitic steel below A1 temperature, followed by intercritical annealing treatment: Hot rolling causes the formation of laminate ferrite and pearlite, as well as the spheroidized carbides located at the ferrite grain boundaries [93]
Summary
There are twins inside the martensite adjacent to ferrite, resulting from the shear deformation of austenite with a high shear strain rate The ferrite phase cannot accommodate this high strain rate, owing to martensitic transformation via dislocations sliding, providing the deformation through the twins. The twins can be formed within the ferrite [67]
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