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Influence of Zr on structure, mechanical and thermal properties of Ti-Al-N.

Chen L, Holec D, Du Y, Mayrhofer PH - Thin Solid Films (2011)

Bottom Line: Here, we study the effect of Zr addition on structure, mechanical and thermal properties of Ti(1-x)Al(x)N based coatings under the guidance of ab initio calculations.Increasing the Zr content from z = 0 to 0.17, while keeping x at ~ 0.5, results in a hardness increase from ~ 33 to 37 GPa, and a lattice parameter increase from 4.18 to 4.29 Å.Furthermore, Zr assists the formation of a dense oxide scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Leoben, 8700, Austria.

ABSTRACT
Multinary Ti-Al-N thin films are used for various applications where hard, wear and oxidation resistant materials are needed. Here, we study the effect of Zr addition on structure, mechanical and thermal properties of Ti(1-x)Al(x)N based coatings under the guidance of ab initio calculations. The preparation of Ti(1-x-z)Al(x)Zr(z)N by magnetron sputtering verifies the suggested cubic (NaCl-type) structure for x below 0.6-0.7 and z ≤ 0.4. Increasing the Zr content from z = 0 to 0.17, while keeping x at ~ 0.5, results in a hardness increase from ~ 33 to 37 GPa, and a lattice parameter increase from 4.18 to 4.29 Å. The latter are in excellent agreement with ab initio data. Alloying with Zr also promotes the formation of cubic domains but retards the formation of stable wurtzite AlN during thermal annealing. This leads to high hardness values of ~ 40 GPa over a broad temperature range of 700-1100 °C for Ti(0.40)Al(0.55)Zr(0.05)N. Furthermore, Zr assists the formation of a dense oxide scale. After 20 h exposure in air at 950 °C, where Ti(0.48)Al(0.52)N is already completely oxidized, only a ~ 1 μm thin oxide scale is formed on top of the otherwise still intact ~ 2.5 μm thin film Ti(0.40)Al(0.55)Zr(0.05)N.

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DSC spectra of powdered Ti1-x-zAlxZrzN films in synthetic air (20 sccm) with a 20 K/min heating rate.
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f0040: DSC spectra of powdered Ti1-x-zAlxZrzN films in synthetic air (20 sccm) with a 20 K/min heating rate.

Mentions: Fig. 8 shows the results of dynamical DSC experiments of powdered freestanding film samples up to 1500 °C in synthetic air, allowing for a qualitative comparison of the temperatures where distinct reactions occur. The Ti0.34Al0.37Zr0.29N film shows the lowest onset temperature (~ 800 °C) of exothermic heat flow of the films investigated, which is mainly attributed to the low Al content (x ~ 0.37) and the high amount of Zr, which is highly affine to O2. The other films with a higher Al content (x ~ 0.5) exhibit the pronounced oxidation reaction at temperatures above 1000 °C with the Zr-containing films exhibiting an additional pre-reaction in the temperature range 870–1030 °C. The latter can especially be observed for Ti0.40Al0.55Zr0.05N. The XRD analyses of Ti0.48Al0.52N and Ti0.40Al0.55Zr0.05N freestanding films after annealing in ambient air at 1000 °C for 1 h, Fig. 9a, indicate that Ti0.48Al0.52N is almost completely oxidized to form rutile, r-TiO2, (with some anatase, a-TiO2,) and α-Al2O3. On the contrary, the XRD pattern of Ti0.40Al0.55Zr0.05N after annealing in air is very similar to that after annealing in vacuum, Fig. 9b, and only small XRD peaks, suggesting the formation of TiO2, α-Al2O3, and Zr0.33Ti0.67O2 can be detected. Consequently, the pre-reaction to the strong exothermic contribution during DSC of Ti0.40Al0.55Zr0.05N (Fig. 8) is assigned to the formation of stable oxides which slow down a further oxidation.


Influence of Zr on structure, mechanical and thermal properties of Ti-Al-N.

Chen L, Holec D, Du Y, Mayrhofer PH - Thin Solid Films (2011)

DSC spectra of powdered Ti1-x-zAlxZrzN films in synthetic air (20 sccm) with a 20 K/min heating rate.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117144&req=5

f0040: DSC spectra of powdered Ti1-x-zAlxZrzN films in synthetic air (20 sccm) with a 20 K/min heating rate.
Mentions: Fig. 8 shows the results of dynamical DSC experiments of powdered freestanding film samples up to 1500 °C in synthetic air, allowing for a qualitative comparison of the temperatures where distinct reactions occur. The Ti0.34Al0.37Zr0.29N film shows the lowest onset temperature (~ 800 °C) of exothermic heat flow of the films investigated, which is mainly attributed to the low Al content (x ~ 0.37) and the high amount of Zr, which is highly affine to O2. The other films with a higher Al content (x ~ 0.5) exhibit the pronounced oxidation reaction at temperatures above 1000 °C with the Zr-containing films exhibiting an additional pre-reaction in the temperature range 870–1030 °C. The latter can especially be observed for Ti0.40Al0.55Zr0.05N. The XRD analyses of Ti0.48Al0.52N and Ti0.40Al0.55Zr0.05N freestanding films after annealing in ambient air at 1000 °C for 1 h, Fig. 9a, indicate that Ti0.48Al0.52N is almost completely oxidized to form rutile, r-TiO2, (with some anatase, a-TiO2,) and α-Al2O3. On the contrary, the XRD pattern of Ti0.40Al0.55Zr0.05N after annealing in air is very similar to that after annealing in vacuum, Fig. 9b, and only small XRD peaks, suggesting the formation of TiO2, α-Al2O3, and Zr0.33Ti0.67O2 can be detected. Consequently, the pre-reaction to the strong exothermic contribution during DSC of Ti0.40Al0.55Zr0.05N (Fig. 8) is assigned to the formation of stable oxides which slow down a further oxidation.

Bottom Line: Here, we study the effect of Zr addition on structure, mechanical and thermal properties of Ti(1-x)Al(x)N based coatings under the guidance of ab initio calculations.Increasing the Zr content from z = 0 to 0.17, while keeping x at ~ 0.5, results in a hardness increase from ~ 33 to 37 GPa, and a lattice parameter increase from 4.18 to 4.29 Å.Furthermore, Zr assists the formation of a dense oxide scale.

View Article: PubMed Central - PubMed

Affiliation: Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Leoben, 8700, Austria.

ABSTRACT
Multinary Ti-Al-N thin films are used for various applications where hard, wear and oxidation resistant materials are needed. Here, we study the effect of Zr addition on structure, mechanical and thermal properties of Ti(1-x)Al(x)N based coatings under the guidance of ab initio calculations. The preparation of Ti(1-x-z)Al(x)Zr(z)N by magnetron sputtering verifies the suggested cubic (NaCl-type) structure for x below 0.6-0.7 and z ≤ 0.4. Increasing the Zr content from z = 0 to 0.17, while keeping x at ~ 0.5, results in a hardness increase from ~ 33 to 37 GPa, and a lattice parameter increase from 4.18 to 4.29 Å. The latter are in excellent agreement with ab initio data. Alloying with Zr also promotes the formation of cubic domains but retards the formation of stable wurtzite AlN during thermal annealing. This leads to high hardness values of ~ 40 GPa over a broad temperature range of 700-1100 °C for Ti(0.40)Al(0.55)Zr(0.05)N. Furthermore, Zr assists the formation of a dense oxide scale. After 20 h exposure in air at 950 °C, where Ti(0.48)Al(0.52)N is already completely oxidized, only a ~ 1 μm thin oxide scale is formed on top of the otherwise still intact ~ 2.5 μm thin film Ti(0.40)Al(0.55)Zr(0.05)N.

No MeSH data available.


Related in: MedlinePlus