Effect of Carbon in Severe Plastically Deformed Metals

Abstract

In the last decades severe plastic deformation techniques have gained increasing interest as they allow the production of bulk nanostructured materials with superior mechanical and functional properties. However, because of mechanically induced grain boundary migration, the achievable grain size reduction is not indefinite but tends to stagnate once sufficient strain has been applied. Consequently, addition of solute elements or second phase particles offers the possibility to access the true nanocrystalline regime. Due to their low solubility and high mobility, interstitial elements are extremely effective at subduing boundary migration. Herein the effect of carbon on grain refinement and the resulting mechanical properties are summarized. As carbon may not only be added as graphite but could also be introduced in other forms or as allotropes such as nanotubes, nanodiamonds, or carbides, the respective advantages and problems associated with it are the center of discussion. Independent of the strategy used, strength levels hardly achievable with other alloying elements can be obtained. Moreover, as carbon does not have a negative effect on grain boundary cohesion, despite the enormous strength levels even ductility and toughness can be widely maintained.

SPD Deformation of Pearlitic, Bainitic and Martensitic Steels

“…However, the tool steel anvils restrict maximum deformability for quasi-constrained HPT to below 800 HV. This is clearly seen in the maximum achievable hardness values of the pearlitic steel grades, which do not exceed the anvil hardness (Figure 7) [44,52]. Once the deformed steels reach the hardness of the anvils, either slippage of the sample within the cavity of the HPT anvils or deformation of the anvil itself occurs.…”

“…Altogether, the structural evolution of steels during HPT yields in a lamellar architecture (Figure 10) with carbon playing a crucial role in stabilizing ferrite interfaces [52]. Yet, the efficiency to achieve structural refinement and so high strength depends on the steel grade that varies in starting architecture (lamellar cementite vs. random carbides), initial grain spacing or chemical composition.…”

The Effect of Severe Plastic Deformation on the Hydrogen Storage Properties of Metal Hydrides

“…7(a)). During this process the sample undergoes plastic deformation, and the equivalent strain can be given as: 85)…”