Stiff, light, strong and ductile: nano-structured High Modulus Steel

H Springer,D Raabe,V Uhlenwinkel,C Baron,A Szczepaniak

doi:10.1038/s41598-017-02861-3

H Springer, D Raabe + Show 3 more

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https://doi.org/10.1038/s41598-017-02861-3

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Abstract

Structural material development for lightweight applications aims at improving the key parameters strength, stiffness and ductility at low density, but these properties are typically mutually exclusive. Here we present how we overcome this trade-off with a new class of nano-structured steel – TiB2 composites synthesised in-situ via bulk metallurgical spray-forming. Owing to the nano-sized dispersion of the TiB2 particles of extreme stiffness and low density – obtained by the in-situ formation with rapid solidification kinetics – the new material has the mechanical performance of advanced high strength steels, and a 25% higher stiffness/density ratio than any of the currently used high strength steels, aluminium, magnesium and titanium alloys. This renders this High Modulus Steel the first density-reduced, high stiffness, high strength and yet ductile material which can be produced on an industrial scale. Also ideally suited for 3D printing technology, this material addresses all key requirements for high performance and cost effective lightweight design.

Highlights

Structural material development for lightweight applications aims at improving the key parameters strength, stiffness and ductility at low density, but these properties are typically mutually exclusive
The specific yield strength (YS) (i.e. YS/ρ) of high performance Mg7, Al8 and Ti alloys[9] is often the more adequate measure for comparing them to high strength steels commonly used in the automotive industry, such as dual-phase[10] or press-hardening steels[11] (Fig. 1b)
After the primary synthesis (Fig. 3) the conventionally produced High Modulus Steels (HMS) (Fig. 3a) exhibits a typical as-cast microstructure[25] with about 15 vol.% of TiB2 particles of irregular shape and size (1–15 μm in diameter) and number density of about 0.06 μm−2 evenly dispersed in a ferritic matrix with a typical widely irregular α-Fe grain size distribution

Summary

Introduction

Structural material development for lightweight applications aims at improving the key parameters strength, stiffness and ductility at low density, but these properties are typically mutually exclusive. Corresponding Fe-based composites, termed High Modulus Steels (HMS), are especially attractive because of the possibility to exploit the numerous phase transformations of steels to tune the mechanical performance, and keep the raw material and production costs to a minimum[19, 20].

Results

Conclusion