Theory of the effects of substitutions on the phase stabilities of Ti1−xAlxN

Hugosson, Håkan Wilhelm; Högberg, Hans; Algren, M.; Rodmar, M.; Selinder, T. I.

doi:10.1063/1.1557779

Cited by 80 publications

(35 citation statements)

References 21 publications

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“…In general, the phase composition of the (Ti, Al) N nanocrystalline coatings is driven by the aluminum contents. [5,11,[20][21][22] However, there is a remarkable spread in the reported solubility limits of Al in fcc-(Ti, Al) N. This was already concluded by PalDey and Deevi, [23] who related the maximum concentration of aluminum in fcc-(Ti, Al) N to the deposition conditions. Recently, the bias voltage was discussed to be a factor influencing the phase composition of the as-deposited Ti-Al-X-N coatings with X = Ta and V (References 24 and 25).…”

Section: Introductionmentioning

confidence: 79%

Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings

Rafaja

Wüstefeld

Baehtz

et al. 2010

Metall Mater Trans A

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The effect of microstructure on the thermal stability and hardness of the cathodic arc evaporated Ti 0.5 Al 0.5 N coatings was investigated with the aid of the in-situ high-temperature X-ray diffraction experiments, which were accompanied by high-resolution transmission electron microscopy (HRTEM) and nanoindentation measurements. The microstructure of the coatings was modified through the choice of the bias voltage in the deposition process. It was found that the bias voltage affects strongly the uniformity of the local distribution of titanium and aluminum in the coatings. The nonuniform distribution of the elements contributes to the formation of lattice strains at the crystallite and phase boundaries. The lattice strains at the crystallite boundaries increase the hardness of the coatings; the lattice strains at the phase boundaries improve their thermal stability. A certain nonuniformity of the distribution of the metallic species in the coatings is regarded as advantageous. However, a great nonuniformity in the distribution of the metallic species accelerates the degradation of the coatings at high temperatures. As a measure for the nonuniformity of the distribution of the atomic species in the as-deposited (Ti, Al) N samples, the stress-free lattice parameter of fcc-(Ti, Al) N is suggested.

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Section: Introductionmentioning

confidence: 79%

Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings

Rafaja

Wüstefeld

Baehtz

et al. 2010

Metall Mater Trans A

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“…5 It has been shown to take place by the formation of coherent Ti-enriched Ti 1−x Al x N regions and cubic AlN nanograins. 5,6 Although significant understanding of the growth processes of transition metal nitrides have been achieved through ab initio calculations 7 and attempts have been made to simulate the effects of alloying on general phase stabilities in the Ti 1−x Al x N system, 8 as well as in nitride based semiconductors, [9][10][11][12] the nature of the decomposition in multicomponent nitride systems is not fully understood. An attempt made in Ref.…”

Section: Introductionmentioning

confidence: 99%

Mixing and decomposition thermodynamics ofc−Ti1−xAlxNfrom first-principles calculations

et al. 2007

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We describe an efficient first-principles method that can be used to calculate mixing enthalpies of transition metal nitrides with B1 structure and substitutional disorder at the metal sublattice. The technique is based on the density functional theory. The independent sublattice model is suggested for the treatment of disorderinduced local lattice relaxation effects. It supplements the description of the substitutional disorder within the coherent potential approximation. We demonstrate the excellent accuracy of the method by comparison with calculations performed by means of the projector augumented wave method on supercells constructed as special quasirandom structures. At the same time, the efficiency of the technique allows for total energy calculations on a very fine mesh of concentrations which enables a reliable calculation of the second concentration derivative of the alloy total energy. This is a first step towards first-principles predictions of concentrations and temperature intervals where the alloy decomposition proceeds via the spinodal mechanism. We thus calculate electronic structure, lattice parameter, and mixing enthalpies of the quasibinary alloy c-Ti 1−x Al x N. The lattice parameter follows Vegard's law at low fractions of AlN but deviates increasingly with increasing Al content. We show that the asymmetry of the mixing enthalpy and its second concentration derivative is associated with substantial variations of the electronic structure with alloy composition. The phase diagram is constructed within the mean-field approximation.

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“…Previous theoretical works used different approaches to understand the physics of Al containing ternary nitrides and focused on the crossing point of the binding energy curves of the cubic and hexagonal structures of the alloys. 14,15 However, the possibility of isostructural decomposition is as important for the understanding of the physics of hard coating nitrides as the decomposition which involves structural modifications. 1,2 In this work we present the result of first-principles calculations of the magnetic properties, electronic structure, lattice parameter, and mixing enthalpy of B1 Cr 1−x Al x N. We compare the results with the recent calculations of Ti 1−x Al x N, 2 as well as with the available experimental data.…”

Section: Introductionmentioning

confidence: 99%

Comparison of thermodynamic properties of cubic Cr1−xAlxN and Ti1−xAlxN from first-principles calculations

Alling

Marten

Abrikosov

et al. 2007

Journal of Applied Physics

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In order to investigate the stability of the cubic phase of Cr 1−x Al x N at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti 1−x Al x N and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr-and Ti-containing systems. Cr 1−x Al x N turns out to be more stable against spinodal decomposition than Ti 1−x Al x N, especially for AlN-rich samples which are of interest in cutting tools applications.

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Theory of the effects of substitutions on the phase stabilities of Ti1−xAlxN

Cited by 80 publications

References 21 publications

Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings

Effect of Internal Interfaces on Hardness and Thermal Stability of Nanocrystalline Ti0.5Al0.5N Coatings

Mixing and decomposition thermodynamics ofc−Ti1−xAlxNfrom first-principles calculations

Comparison of thermodynamic properties of cubic Cr1−xAlxN and Ti1−xAlxN from first-principles calculations

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