Altered and gangue quartz in hydrothermal veins from the Kubi Gold deposit in Dunkwa on Offin in the central region of Ghana are investigated for possible Au-associated indicator minerals and to provide the understanding and increase the knowledge of the mineral hosting and alteration processes in quartz. X-ray diffraction, air annealing furnace, differential scanning calorimetry, energy dispersive X-ray spectroscopy, and transmission electron microscopy have been applied on different quartz types outcropping from surface and bedrocks at the Kubi Gold Mining to reveal the material properties at different temperatures. From the diffraction results of the fresh and annealed quartz samples, we find that the samples contain indicator and the impurity minerals iron disulfide, biotite, titanium oxide, and magnetite. These minerals, under oxidation process between 574 and 1400 °C temperatures experienced hematite alterations and a transformation from α-quartz to β-quartz and further to cristobalite as observed from the calorimetry scans for hydrothermally exposed materials. The energy dispersive spectroscopy revealed elemental components of Fe, S, Mg, K, Al, Ti, Na, Si, O, and Ca contained in the samples, and these are attributed to the impurity phase minerals observed in the diffraction. The findings also suggest that during the hydrothermal flow regime, impurity minerals and metals can be trapped by voids and faults. Under favorable temperature conditions, the trapped minerals can be altered to change color at different depositional stages by oxidation and reduction processes leading to hematite alteration which is a useful indicator minerals in mineral exploration.

We report on phase and strain changes in Ti_1-xAl_xN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.

The defect structures forming during high-temperature decomposition of Ti1-xAlxNy films were investigated through high-resolution scanning transmission electron microscopy. After annealing to 950 °C, misfit edge dislocations a/6〈112〉{111} partial dislocations permeate the interface between TiN-rich and AlN-rich domains to accommodate lattice misfits during spinodal decomposition. The stacking fault energy associated with the partial dislocations decreases with increasing Al content, which facilitates the coherent cubic to wurtzite structure transition of AlN-rich domains. The wurtzite AlN-rich structure is recovered when every third cubic {111} plane is shifted by along the [211] direction. After annealing to 1100 °C, a temperature where coarsening dominates the microstructure evolution, we observe intersections of stacking faults, which form sessile locks at the interface of the TiN- and AlN-rich domains. These observed defect structures facilitate the formation of semicoherent interfaces and contribute to hardening in Ti_1-xAl_xN_y.

Structural changes in Ti_1-xAl_xN coated tool inserts used for turning in 316L stainless steel were investigated by XANES, EXAFS, EDS, and STEM. For coarse-grained fcc-structured Ti_1-xAl_xN coatings, with 0 ≤ x ≤ 0.62, the XANES spectrum changes with Al-content. XANES Ti 1s line-scans across the rake face of the worn samples reveals that TiN-enriched domains have formed during turning in Ti_0.47Al_0.53N and Ti_0.38Al_0.62N samples as a result of spinodal decomposition. The XANES spectra reveal the locations on the tool in which the most TiN-rich domains have formed, indicating which part of the tool-chip contact area that experienced the highest temperature during turning. Changes in the pre-edge features in the XANES spectra reveal that structural changes occur also in the w-TiAlN phase in fine-grained Ti_0.38Al_0.62N during turning. EDS shows that Cr and Fe from the steel adhere to the tool rake face during machining. Cr 1s and Fe 1s XANES show that Cr is oxidized in the end of the contact length while the adhered Fe retains in the same fcc-structure as that of the 316L stainless steel.

Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterizedthin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. Byhigh-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besidesthe expected primary a/2{110}h110i dislocation, Shockley partial dislocations a/6{111}h112i and sessileLomer edge dislocations a/2{100}h011i. Density-functional theory and classical interatomic potentialsimulations complement STEM observations by recovering the atomic structure of the different disloca-tion types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core.The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakenedTi-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}h110i and {111}h112idislocations. Our findings underscore that the presence of different dislocation types and their effects onchemical bonding should be considered in the design and interpretations of nanoscale and macroscopicproperties of TiN.

The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at similar to 750-800 degrees C, followed by decomposition of the alpha-Cr2O3 structure in conjunction with bcc-Cr formation, starting at similar to 950 degrees C. The resulting coating after annealing to 1140 degrees C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at similar to 750 degrees C. The resulting coating after annealing to 975 degrees C is a mixture of t-ZrO2 and alpha-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with alpha-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 degrees C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.

The effect of metal alloying on mechanical properties including hardness and fracture toughness were investigated in three alloys, Ti 0.33Al0.50(Me) 0.17N (Me = Cr, Nb and V), and compared to Ti0.50Al0.50N, in the as-deposited state and after annealing. All studied alloys display similar as-deposited hardness while the hardness evolution during annealing is found to be connected to phase transformations, related to the alloy’s thermal stability. The most pronounced hardening was observed in Ti0.50Al0.50N, while all the coatings with additional metal elements sustain their hardness better and they are harder than Ti0.50Al0.50N after annealing at 1100 °C. Fracture toughness properties were extracted from scratch tests. In all tested conditions, as-deposited and annealed at 900 and 1100 °C, Ti0.33Al0.50Nb0.17N show the least surface and sub-surface damage when scratched despite the differences in decomposition behavior and h-AlN formation. Theoretically estimated ductility of phases existing in the coatings correlates well with their crack resistance. In summary, Ti0.33Al0.50Nb0.17N is the toughest alloy in both as-deposited and post-annealed states.

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (greater than50 keV), high photon flux (greater than10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (less than1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (less than11 degrees), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument. (C) 2015 AIP Publishing LLC.

Ti1_−xAl_xN is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the newly developed symmetry imposed force constant temperature dependent effective potential method, that include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C₁₁ decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.

We study the thermal stability of wurtzite (w) structure ZrAlN coatings by a combination of in situ high-energy x-ray scattering techniques during annealing and electron microscopy. Wurtzite structure Zr1-xAlxN coatings with Al-contents from x = 0.46 to x = 0.71 were grown by cathodic arc evaporation. The stability of the w-ZrAlN phase depends on chemical composition where the higher Al-content coatings are more stable. The wurtzite ZrAlN phase was found to phase separate through spinodal decomposition, resulting in nanoscale compositional modulations, i.e., alternating Al-rich ZrAlN layers and Zr-rich ZrAlN layers, forming within the hexagonal lattice. The period of the compositional modulations varies between 1.7 and 2.5 nm and depends on the chemical composition of the coating where smaller periods form in the more unstable, high Zr-content coatings. In addition, Zr leaves the w-ZrAlN lattice to form cubic ZrN precipitates in the column boundaries. (C) 2015 AIP Publishing LLC.