Ductile high strength steel developed in WMG project

Test: The ductile vs brittle fracture of steel The cup and cone fracture shows the plasicity and ductility exhibited in the lower strength steel, while the high strength steel's brittle fracture snaps, which is more akin to glass
A project funded by the WMG centre for High Value Manufacturing (HVM) Catapult has developed a process to make high-strength steel without the usual trade-off of increased brittleness.

Researcher, Dr Alireza Rahnama, developed the processing that allows low density steel-based alloys to be produced with ‘maximum strength’, whilst remaining durable and flexible – something that has remained largely impossible until now.

Current processes for strengthening steels make them less flexible, which in turn makes them less applicable to wider industry.

Dr Rahnama, said: “Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. Lightweight steels are one of the candidates to address these concerns.”

Two lightweight steels were tested for their potential to achieve maximum strength and ductility: Fe-15Mn-10Al-0.8C-5Ni and Fe-15Mn-10Al-0.8C.

During production, two brittle phases can occur in these steels: kappa-carbide (k-carbide) and B2 intermetallic. These make the steels hard, but limit their ductility, making them difficult to process using traditional means such as hot or cold rolling.

Through simulation and then experimentation, the WMG researcher group found that at certain high annealing temperatures, the brittle phases become much more controllable, allowing the steels to retain their ductility.

Between 900°C to 1200°C, the k-carbide phase can be removed from production, and the B2 intermetallic brittle phase can become manageable, forming in a disk-like, nano-sized morphology, as opposed to the coarser product that forms at lower temperatures.

Dr Rahnama, said: “Most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. This paper studies the kinetics and thermodynamics of microstructural evolution of lightweight steels through simulations and experiments and proposes a mechanism to achieve higher strength and larger ductility; a method that can be readily adopted by industry.”

The research, ‘Effect of Ni alloying on the microstructural evolution and mechanical properties of two duplex light-weight steels during different annealing temperatures: experiment and phase-field simulation’, is published in Acta Materialia.

It is co-authored by Dr Hiren Kotadia and Professor Seetharaman Sridhar.

Author
Justin Cunningham

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Advanced high-strength steels have both excellent strength and ductility.

Comment Satyam Impex, 16/11/2017
Enjoyed reading the article above, really explains everything in detail. This article discusses the development of Ductile high strength steel & its importance.

Comment bhairavsteel, 02/11/2017
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