High temperature decomposition and age hardening of single-phase wurtzite Ti1−x_{1-x}Alx_{x}N thin films grown by cathodic arc deposition

We investigated the high temperature decomposition behavior of wurtzite phase Ti$_{1-x}$Al$_{x}$N films using experimental methods and first-principles calculations. Single phase metastable wurtzite Ti$_{1-x}$Al$_{x}$N (x = 0.65, 0.75, 085 and 0.95) solid solution films were grown by cathodic arc deposition using low duty cycle pulsed substrate-bias voltage. First-principles calculated elastic constants of the wurtzite Ti$_{1-x}$Al$_{x}$N phase show a strong dependence on alloy composition. The predicted phase diagram shows a miscibility gap with an unstable region. High resolution scanning transmission electron microscopy and chemical mapping demonstrate decomposition of the films after high temperature annealing (950$^{\circ}$C), which resulted in nanoscale chemical compositional modulations containing Ti-rich and Al-rich regions with coherent or semi coherent interfaces. This spinodal decomposition of the wurtzite film causes age hardening of 1-2 GPa

Decomposition routes and strain evolution in arc deposited TiZrAlN coatings

Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti$_{0.31}$Zr$_{0.24}$Al$_{0.45}$N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, −1.1%, which are retained after 3 h at 1100 °C. In coatings with higher Zr-content, the strains relax during annealing above 900 °C due to grain growth and defect annihilation

Decomposition routes and strain evolution in arc deposited TiZrAlN coatings

Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti0.31Zr0.24Al0.45N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, -1.1%, which are retained after 3 h at 1100 degrees C. In coatings with higher Zr-content, the strains relax during annealing above 900 degrees C due to grain growth and defect annihilation. (C) 2018 Elsevier B.V. All rights reserved.Funding Agencies|VINNOVA (Swedish Governmental Agency for Innovation Systems) [2016-05156]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Research Council [2017-03813]; Rontgen-Angstrom Cluster frame grants [VR 2011-6505, VR 2017-06701]</p

Protection of Investors in Gulf Cooperation Council Stock Markets: A Case Study of Kuwait, Bahrain and United Arab Emirates

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Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys

The phase evolution of cubic (c), solid solution Ti$_x$Cr$_{~0.37}$Al$_{1-0.37-x}$N alloys with x ¼ 0.03 and 0.16, and thekinetics of the hexagonal (h)-AlN formation are studied via in situ wide angle x-ray scattering experimentsduring high temperature (1000e1150 C) annealing. Spinodal decomposition was observed inTi$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N while Ti$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N decomposes through nucleation and growth of h-AlN, c-TiNand c-CrAlN. h-AlN is formed from c-CrAlN domains in both cases and the formation rate of h-AlN dependson the stability of the c-CrAlN domains. In Ti$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N, the c-CrAlN domains are stabilized bycrystallographic coherency with the surrounding c-TiCrN in a microstructure originating from spinodaldecomposition. This results in lower formation rates of h-AlN for this composition. These differences arereflected in higher activation energy for h-AlN formation in Ti$_{0.16}$Cr$_{0.36}$Al$_{0.48}$N compared toTi$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N. It also points out different stabilities of the intermediate phase c-CrAlN during phasedecomposition of TiCrAlN alloys. Additional contributions to the low activation energy for formation ofh-AlN in Ti$_{0.03}$Cr$_{0.38}$Al$_{0.59}$N stems from precipitation at grain boundaries