研究目的
Investigating the dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides, specifically Al0.7Cr0.3N thin films, using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction.
研究成果
The study demonstrates that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides. The decomposition process starts at the same stress level of ~?4300 MPa in all three films, indicating that this compressive stress level functions as an energy threshold for the diffusion-driven formation of hexagonal Al(Cr)N phase. The unique synchrotron experimental setup provided comprehensive insights into the thermal stability and phase evolution of Al0.7Cr0.3N thin films.
研究不足
The study is limited to Al0.7Cr0.3N thin films and does not explore other compositions or materials. The experiments were conducted under specific conditions (vacuum at ptotal < 10?2 mbar) which may not represent all operational environments. The high heating rate and exposure time may introduce uncertainties in the determination of onset temperatures of phase decomposition.
1：Experimental Design and Method Selection
In-situ high-temperature high-energy grazing incidence transmission X-ray diffraction (HT-HE-GIT-XRD) was used to study the temperature-dependent behavior of Al0.7Cr0.3N films and WC-Co substrates. The methodology included heating the samples to 1100 °C at a rate of 1 K/s followed by a holding segment of 300 s at the maximum temperature and subsequent cooling to room temperature (RT) at a rate of ~1 K/s.
2：Sample Selection and Data Sources
Three Al0.7Cr0.3N thin films with residual stress magnitudes of ?3510, ?4660 and ?5930 MPa in the as-deposited state were characterized. The films were deposited on mirror-polished cemented carbide (WC, 6 wt.% Co) substrates.
3：List of Experimental Equipment and Materials
The experiments were performed at the P07B beamline of the PETRA III synchrotron source in Hamburg (D) in transmission geometry, using a pencil X-ray beam with a size of 400 × 100 μm2 and an energy of 87.1 keV. A DIL 805 dilatometer (TA Instruments) was used for mounting the samples. A Perkin-Elmer detector with a pixel size of 200 × 200 μm2 was used for recording the diffraction patterns.
4：Experimental Procedures and Operational Workflow
The samples were mounted into the dilatometer with the surface aligned with respect to the primary beam at an incidence angle β of ~2 deg. The thermal cycle included heating to 1100 °C at a rate of 1 K/s followed by a holding segment of 300 s at the maximum temperature and subsequent cooling to RT at a rate of ~1 K/s. Two-dimensional X-ray diffraction patterns were recorded continuously with an exposure time of ~25 s per frame.
5：Data Analysis Methods
The detector calibration was performed using a LaB6-powder and the Fit2D software package. The 2D data evaluation was performed using the pyFAI software package. The temperature and phase evolution during one temperature cycle were analyzed by integrating the diffraction signal from the detector in the azimuthal angle range δ from ?180 to 0 deg.
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