Quantitative Characterization of Heat Treatment Response in a Single Crystal Nickel-Based Superalloy

To study quantitatively the effect of heat treatment on the microstructure, composition and mechanical property in a new single crystal nickel-based superalloy for industrial gas turbine (IGT) applications, the eutectic fraction, carbide fraction, and the fraction, size, shape and distribution of the γ ́ phase was characterized by quantitative metallographic method, the evolution of chemical composition and hardness between core and inter dendrite was tested through EMPA and nanoindentation. The experimental results indicate that: The eutectic fraction decreases from (0.52±0.08) % to (0.03±0.01) %. The carbides fraction decreases from (0.23±0.04) % to (0.12±0.03) %, and Feret ratio decreases from 3.21±2.54 to 2.14±0.98. The γ ́ fraction increases from (55.66±4.18) % to (73.78±3.24) % in core dendritic region, from (64.82±1.44) % to (70.11±3.10) % in inter dendritic region. The γ ́-size is 406±111(nm) in core dendritic region and 918±384(nm) in inter dendritic region before heat treatment, 359±69(nm) in core dendritic region and 361±57(nm) in inter dendritic region after heat treatment. The γ ́-cuboidal degree is 1.08±0.20 in core dendritic region and 1.14±0.23 in inter dendritic region before heat treatment, 1.08±0.19 in core dendritic region and 1.02±0.14 in inter dendritic region after heat treatment. The solidification segregation coefficient of main segregation elements, such as Re, W, Hf, Ta, Al, and Mo, is closer to 1, with an average decrease of 27% after heat treatment. The hardness and modulus increase in core and inter dendritic, and their inhomogeneity is reduced between cores and inter dendritic. The improvement of properties result from the improvement of size uniformity and cuboidal degree of γ ́, and the reduction of carbides and eutectic through element homogeneity during heat treatment. The solidification segregation coefficient of main segregation elements, such as Re, W, Hf, Ta, Al, and Mo, is closer to 1, with an average decrease of 27% after heat treatment. With the addition of refractory elements, some elements partition to the dendrite core, while other elements tend to accumulate in the interdendritic liquid and then solidify as the interdendritic and eutectic regions during solidification. The hardness and modulus increase in core and inter dendritic, and their inhomogeneity is reduced between cores and inter dendritic. The improvement of properties result from the improvement of size uniformity and cuboidal degree of γ ́, and the reduction of carbides and eutectic through element homogeneity during heat treatment.

Scintillation and Energy-Storage Properties of Micro-Pulling-Down Grown Crystals of Sc3+- and La3+-Doped YAlO3 Perovskite

The scintillation and energy-storage properties of YAlO3 (YAP) crystals doped with Sc3+ and La3+ isoelectronic dopants were investigated in this work. The YAP:Sc and YAP:La crystals were grown from the melt with a nominal Sc and La content in the 0.2–5.0 mol.% range using the novel micro-pulling-down method. We found that the segregation coefficient of Sc ions in YAP:Sc (0.2–1.0 mol.%) crystals is about of 0.35–0.4 and decreases to around 0.2 at Sc content of 5.0 mol.% when the segregation coefficient of La ions in YAP:La (1.0–5.0 mol.%) crystals is 0.008–0.01. The scintillation and stimulated luminescence phenomena, like thermo- and photoluminescence, were utilized for the property characterization of the studied materials. The cathodoluminescence and X-ray-excited luminescence were used for the imitation of scintillation in the YAP:Sc and YAP:La crystals. The influence of Sc3+ and La3+ dopant concentration on the CL and RL emission spectra, as well as the shape of the measured thermoluminescence (TL) glow-curves, was also investigated. The measured emission spectra showed dominant emission of Sc3+ and La3+ ions in the UV range. For this reason, the YAP:Sc and YAP:La crystals can be considered for creation of ultraviolet (UV)-emitting scintillators. For the undoped YAlO3 crystals, the main TL emission peak occurs in a low-temperature range at 375 K. Meanwhile, even a small addition of dopants causes a strong suppression of luminescence of the YAP host and high-temperature peaks become dominant in the TL glow-curves of YAP:Sc and YAP:La crystals. Moreover, the amplitude of emission does not change monotonically with increasing dopant content. The kinetic parameters of emission were also evaluated, and the first-order behavior was confirmed in all cases. The dosimetric properties of investigated materials such as dose response, fading rate, and the lowest measurable dose are also discussed. The obtained results tend to suggest that the YAlO3 perovskite host, apart from its application for the development of efficient scintillators, may also be considered as a promising matrix for the creation of energy-storage phosphors for dosimetric applications.

EVALUATING GEOCHEMISTRY OF RARE EARTH ELEMENTS IN COPPER DEPOSIT OF AGHBOLAGH, NORTH OF OSHNAVIEH, WEST AZARBAIJAN PROVINCE-IRAN

AghBolagh region is located in southwest of West Azarbaijan Province that is 10 km far from north of Oshnavieh. Most of the rocky outcrops in the region include Cambrian deposits (carbonate deposits and clastic deposits (sandstone and shale)). These deposits were later influenced and altered by granite Intrusion. The Intrusion is made of granite and in term of nature, it is magmatic with High-potassium calc-alkaline and peralumin. Also the penetration of intrusion and Ore maker solvent in further distances from the contact point and inside the sequences of sandstone has formed quartzite rocks and ore bearing veins of cooper. The REE pattern normalized to Chondrite for granite, skarn, and marble intrusion and vein deposits shows the fact that, although the REEs pattern is a little smooth and unified, LREEs have more enrichment compared to HREEs in different lithology. The range of normalized numbers to Chondrite in AghBolagh deposit is clearly variable (2.58 to 141.93 for La and 0.14 to 27.27 for Yb). This indicates that there have been clear differences in increase and decrease of LREEs and HREEs during the formation of AghBolagh deposit stones and rocks. The La / Y ratio shows the pH condition of the environment for formation of deposit. This ratio in AghBolagh deposit ranges from 0.09 to 2.26. The granite intrusion shows the most amount of La/Y which is equal to 2. Skarn Zone (Endoskarn and Exoskarn and Ore in Exoskarn) shows two different conditions. The first condition: the part in which LA/Y>1, and this can be observed in samples near the intrusion and Skarn ore is also found in this range. The second condition: the part that La/Y<1, which is near to marble lithology. Also, about vein deposit, the sample is ore making in alkaline conditions, and other samples show acidic conditions. To evaluate the segregation coefficient between REEs, different ratios of REEs including (La/Yb) n ', (La/Sm) n, and (Gd/Yb) n are used. The values of these ratios range from (0.42 to 50.56) for (La/Yb) n; and from (0.25 to 80.125) for (La/Sm) n’; (from 0.006 to 48.8) for (Gd/Yb) n. The highest segregation was between LREEs and HREEs (more than 125) and the least segregation was between MREEs and HREEs during the Skarn process.

The effects of deuteration-levels in solution and temperature on the segregation coefficient of the deuterium content in rapid-grown K(DxH1−x)2PO4 crystals via Raman spectroscopy

The correlation between the deuterium segregation coefficient and temperature, and the deuterium content in a solution was studied for the first time.

Bridgman Growth of New Nonlinear Optical Crystal (La1 − xSmx)3Ga5.5Nb0.5O14 for Quasi-Parametric Chirped Pulse Amplification

Samarium-doped La3Nb0.5Ga5.5O14 (Sm:LGN) crystals were grown along a (100)-orientation by the Bridgman method for quasi-parametric chirped pulse amplification (QPCPA) applications. The structure of La1-xSxmGN (x = 0.1, 0.2) crystals was the same as that of La3Nb0.5Ga5.5O14 (LGN) crystals. The effective segregation coefficient of Sm3+ in the La0.9Sm0.1GN crystal was 0.140. The full width at half maximum (FWHM) of La1-xSxmGN (x = 0.1,0.2) crystals was lower than 50″, which indicated the high quality of the crystals. The density of the La0.9Sm0.1GN crystal was 5.968 g/cm3 and that of the La0.8Sm0.2GNcrystal was 5.988 g/cm3. The transmittance of the crystals at 532nm and 800nm was all above 73%. The absorption spectra indicated that the crystals had strong absorption peaks at wavelengths of 1544 and 1595 nm. The thermal properties of La1-xSxmGN (x = 0.1, 0.2) crystals were similar to those of the LGN crystals. The laser damage thresholds of La0.9Sm0.1GN and La0.8Sm0.2GN crystals were, respectively, 188.30 and 54.84 TW/cm2 (@800 nm,35 fs).

Effect of [Li]/[Nb] ratios on segregation coefficient and dopant occupancy of In:Yb:Nd:LiNbO3 crystals

A series of [Formula: see text] crystals with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38) were grown by the Czochralski method. They were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). As the [Li]/[Nb] ratio increases in the melt, the segregation coefficients of [Formula: see text] and [Formula: see text] ions increase, while the segregation coefficient of [Formula: see text] ions decrease. The [Li]/[Nb] ratio in the crystal of sample [Formula: see text] is 0.996, which is near stoichiometric. The dopant occupancy with different [Li]/[Nb] ratios was analyzed by IR transmission spectrum and UV-VIS-NIR spectrum. When the [Li]/[Nb] ratio reaches 1.20, the absorption peak at [Formula: see text] indicates that the threshold concentration of [Formula: see text] is 1 mol.% in the sample [Formula: see text].

Consequences of microphysical segregation of chemical elements in welded steels

Defects of metallurgy-originated steel (sub-cored bubbles, impurities, macro- and micro-segregations of chemical elements, nonmetallic inclusions) to a large extent determines the faultiness of metal rolled products. The processes of chemical elements segregation in steel macro- and micro volumes considerably influence its quality. Reasons of microphysical dendrite segregation originating in steels of welding purpose of Св-09Г2С and Св-08ГНМ type considered. Mechanism of dendrites formation studied as well as the segregation degree of chemical elements along the continuously casted billet cross section. To estimate the segregation degree a criteria was used – the segregation coefficient, determined as relation of chemical elements mass shares in different micro-areas (dendrites, inter-dendrite gaps) of continuously casted billet cross section to those elements content by a ladle analysis of a heat or one another in different micro-areas. A heredity of segregation transfer from CC billet to finished wire rod of Св-08Г2С and Св-08ГНМ steels studied. It was determined, that decrease of the number of bainite-martensite areas as a result of decrease of dendrite segregation of chemical elements takes place by minimization within grade chemical composition of both main alloying element and impurities ones. Besides an additional alloying of steel by boron takes place based on boron to nitrogen relation at the level of B/N = 0,8±0,15. It was shown that to decrease the inter-dendrite segregation it is necessary to elaborate and implement effective steel modifying by calcium and REMs regimes as well as electro-magnetic stirring during continuous casting.

Investigation of Ce-=SUP=-3+-=/SUP=- impurity centers in UV active media Ce:LiCaAlF-=SUB=-6-=/SUB=- and Ce:LiSr-=SUB=-0.8-=/SUB=-Ca-=SUB=-0.2-=/SUB=-AlF-=SUB=-6-=/SUB=- -=SUP=-*-=/SUP=-

Fluoride crystals with the colquiriite structure LiCaAlF6 doped with Ce3+ ions are used as active media for lasers of ultraviolet spectral range with advantages of laser wavelength tuning range and no photoinduced degradation of laser properties. In this work we show that the multicenter character of Ce3+ segregation in this matrix agrees with the previously known peculiarities. On the basis of spectral-kinetic properties investigation, we show the increase of segregation coefficient for Ce3+ in LiSr0.8Ca0.2AlF6 mixed crystal. In laser experiments with Ce : LiCaAlF6 crystal, the differential efficiency of 47% and the wavelength tuning from 281 to 312 nm have been reached.

A Facile and Low-Cost Method to Produce Ultrapure 99.99999% Gallium

As one of the critical raw materials, very pure gallium is important for the semiconductor and photoelectric industry. Unfortunately, refining gallium to obtain a purity that exceeds 99.99999% is very difficult. In this paper, a new, facile and efficient continuous partial recrystallization method to prepare gallium of high purity is investigated. Impurity concentrations, segregation coefficients, and the purification effect were measured. The results indicated that the contaminating elements accumulated in the liquid phase along the crystal direction. The order of the removal ratio was Cu > Mg > Pb > Cr > Zn > Fe. This corresponded to the order of the experimentally obtained segregation coefficients for each impurity: Cu < Mg < Pb < Cr < Zn < Fe. The segregation coefficient of the impurities depended strongly on the crystallization rate. All observed impurity concentrations were substantially reduced, and the purity of the gallium obtained after our refinement exceeded 99.99999%.

Effective Diffusion Coefficient

The diffusion of a B element into an A matrix was studied by the random walk theory. Considering that concentration of B element in the A matrix is very low, the jumps of diffusing atoms are independent of each other. The A matrix is a two-region material with different properties, such as a two-phase material, a single crystal with dislocations, or regions influenced by other solute and a polycrystalline material.It is assumed that material B has a penetration that allows it to cross each region of material A several times. This implies that jumps across the surface between those regions have an average frequency and, as a consequence, there is an interdiffusion coefficient between them. The interdiffusion coefficient between those regions is different than the coefficient of the diffusion in each region.Expressions were obtained that allow to delimit the ranges of validation with greater precision than the corrected Hart-Mortlock equation for solute diffusion. In addition, an original relationship was obtained between the segregation coefficient and parameters specific to the diffusion. New powerful tools were also found that can help to understand diffusion in nanocrystalline materials, diffusion in metals influenced by impurities and diffusion produced by different mechanisms.