Editorial: New Developments and Challenges in Advanced High-Strength Steels

New Developments and Challenges in Advanced High-Strength SteelsSteel is a globally-used structural material and a major factor in advancing societies and economies.Advanced high-strength steels (AHSS) are a class of high-performance steels particularly important to the automotive industry due to the increased need for fuel efficiency, emissions reduction and passive safety.The research topic "New Developments and Challenges in Advanced High-Strength Steels" aims at collecting state-of-the-art research studies on design, processing and characterization of AHSS.This issue comprises seven peer-reviewed research articles covering a wide range of steel types like medium manganese (Mn) steel, twinning induced plasticity (TWIP) steel, transformation induced plasticity (TRIP) steel, quenched and partitioned (Q&P) steel, low-carbon ferrite steel and press-hardened steel.Among these studies, the influence of heat treatment routes on the microstructure and mechanical property of AHSS were extensively investigated and some new processing routes were proposed.Pan and He achieved three microstructural combinations of ferrite, austenite and/or martensite by varied heat treatment including intercritical annealing (IA), quenching and partitioning (Q&P), and a combination of IA and Q&P.The variation in volume fraction and stability of retained austenite was compared between those microstructures.Different combinations of high strength and high elongation were obtained by adjusting the processing route, illustrating how the tensile properties of medium Mn steel can be tuned to facilitate its applicability to a broad range of automotive needs.Glover et al. proposed novel processing routes to improve the mechanical properties of a medium Mn steel.The addition of either a tempering or austempering heat treatment to double soaking of a medium Mn steel was shown to increase the strength-ductility product as compared to a single intercritical annealing heat treatment.This work highlights additional opportunities to modify the mechanical properties of medium Mn steels.It is well-known that grain refinement can improve the strength of steels.Severe plastic deformation (SPD) processes are commonly employed to create UFG microstructures with average grain sizes smaller than 1 μm.However, there exists big difficulty in scaling up the SPD approaches for mass steel production.Park et al. conducted a novel cyclic heat treatment to generate UFG ferrite in a 2 Mn-0.1 C steel.The cyclic heat treatment was proved to be effective for decreasing the austenite grain size to 11 μm.A finegrained ferrite structure with a mean grain size of 4.5 μm and nearly a random texture was successfully obtained only through the cyclic heat treatment and provided both high strength and large tensile ductility.

Abstract licence: CC BY

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