Effect of the size of transition-metal aluminides on the structure of 1570C aluminum alloy processed by hot multidirectional isothermal forging

1996 ◽

Vol 54 ◽

pp. 522-523

Author(s):

G.A. Botton ◽

C.J. Humphreys

Keyword(s):

High Temperature ◽

Transition Metal ◽

Energy Loss ◽

Grain Boundaries ◽

Industrial Applications ◽

Edge Structure ◽

Structural Applications ◽

Yield Behaviour ◽

Late Transition ◽

Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

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First-principle investigations of structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides

Materials Science-Poland ◽

10.1515/msp-2015-0033 ◽

2015 ◽

Vol 33 (2) ◽

pp. 251-258

Author(s):

Bendouma Doumi ◽

Allel Mokaddem ◽

Mustapha Ishak-Boushaki ◽

Miloud Boutaleb ◽

Abdelkader Tadjer

Keyword(s):

Transition Metal ◽

Electronic Properties ◽

Density Functional ◽

First Principle ◽

Generalized Gradient ◽

Metallic Behavior ◽

Plane Wave Method ◽

Structural And Electronic Properties ◽

The Difference ◽

Metal Aluminides

AbstractIn the present work, we have investigated the structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides in the B2 structure, using first-principle calculations of the density functional theory (DFT) based on the linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k code, in which the energy of exchange and correlation are treated by the generalized gradient approximation (GGA), proposed in 1996 by Perdew, Burke and Ernzerhof (PBE). The ground state properties have been calculated and compared with other calculations, and the electronic structures of all FeAl, CoAl, and NiAl compounds exhibited a metallic behavior. It was depicted that the density of states is characterized by the large hybridization between the s-p (Al) and 3d (Fe, Co, and Ni) states, which creates the pseudogap in the region of anti-bonding states. Moreover, the band structures of FeAl, CoAl, and NiAl are similar to each other and the difference between them is in the energy level of each band relative to the Fermi level.

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