Thursday, February 5, 2015

A new recipe for low-density steel that has a combination of strength and malleability beyond that of the lightest, strongest known metals is reported in Nature


Brittle intermetallic compound makes ultrastrong low-density steel with large ductility

Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 . This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others

a, As-cold-rolled microstructure consisting of austenite matrix (γ) and B2 stringer bands. RD, rolling direction; ND, normal direction. b, Annealed microstructure having fine B2 precipitates in between the retained B2 bands in austenite matrix. c, Scanning TEM image of the annealed high-specific-strength steel (HSSS) showing morphologies of B2 particles. The inset shows the selected area diffraction pattern of a B2 precipitate. d, Partitioning of alloying elements between B2 precipitate and austenite matrix. e, Sketches illustrating the formation mechanism of B2 precipitates of types 2 and 3 in b.


Read original article at A lighter, stronger, flexible steel

About the Author

Prejeesh Sreedharan

Author & Editor

I am a Biotechnologist very much interested in #SciTech (Science And Technology). I closely follow the developments in medical science and life science. I am also very enthusiast in the world of electronics, information technology and robotics. I always looks for ways to make complicated things simpler. And I always believes simplest thing is the most complicated ones.

 
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