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Journal articles on the topic 'Single-Crystal casting'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Toloraya, V. N., and G. A. Ostroukhova. "Production of single-crystal seeds [001] from nickeltungsten alloys by directional crystallization." Voprosy Materialovedeniya, no. 2(106) (August 1, 2021): 55–65. http://dx.doi.org/10.22349/1994-6716-2021-106-2-55-65.

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The problem of obtaining priming materials from Ni-W alloys arose in connection with the development of technology for casting single-crystal turbine blades of gas turbine engines (GTE) from hightemperature alloys. This technology uses a seed method for producing single-crystal castings with a crystallographic orientation [001] using seedings from alloys of the Ni-W system with a melting point 120–140°C higher than the casting alloy. The use of such primers greatly simplifies the casting process of turbine blades with a single-crystal structure, increases its reliability both in pass-through furnaces of the PMP-2 type and in high-gradient furnaces of the UVNK-9A type. The article presents the results of the study of the influence of temperature-velocity parameters of directional crystallization, namely, the temperature gradient GZ on the structure of the obtained single-crystal seed blanks, as well as the study of effects of tungsten and carbon on the structure of single-crystal seed blanks, and makes recommendations for optimizing the technological process of single-crystal casting of Ni–W seed blanks adjusting the alloy composition for the seed blanks.

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2

Xu, Qing Yan, Bai Cheng Liu, Zuo Jian Liang, Jia Rong Li, Shi Zhong Liu, and Ha Llong Yuan. "Modeling of Unidirectional Growth in a Single Crystal Turbine Blade Casting." Materials Science Forum 508 (March 2006): 111–16. http://dx.doi.org/10.4028/www.scientific.net/msf.508.111.

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Single crystal superalloy turbine blade are widely used in aero-engineering. However, there are often grain defects occurring during the fabrication of blade by casting. It is important to study the formation of microstructure related defects in turbine blades. Single crystal blade sample castings of a nickel-base superalloy were produced at different withdrawal rates by the directional solidification process and investment casting. There was a difference between the microstructure morphology at the top part of the turbine blade sample castings and the one at the bottom. Higher withdrawal rates led to more differences in the microstructure and a higher probability of crystallographic defect formation such as high angle boundaries at locations with an abrupt change of the transversal section area. To further investigate the formation of grain defects, a numerical simulation technique was used to predict the crystallographic defects occurring during directional solidification. The simulation results agreed with the experimental ones.

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3

Yu, K. O., J. A. Oti, and W. S. Walston. "Investment casting of NiAl single-crystal alloys." JOM 45, no. 5 (May 1993): 49–51. http://dx.doi.org/10.1007/bf03223220.

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4

Jin, H. P., Jia Rong Li, and Shi Zhong Liu. "Simulation of the Solidification Parameters of Single Crystal Casting." Materials Science Forum 638-642 (January 2010): 2251–56. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2251.

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The effects of thermal physical parameters and boundary conditions on investment solidification parameters were obtained using a computer simulation system. Directional solidification parameters of single crystal superalloy include the temperature distribution, the position and the shape of the solid/liquid interface in the mushy zone of the solidifying blade casting. Commercial finite-element analysis software, ProCAST, was used to simulate the solidification processes of the castings of single crystal DD6. The simulation results indicate that the predictions of the temperature show little sensitivity to the thermal physical parameters and boundary conditions. Further, it has also been shown that the location and the shape of solid/liquid interface is related to the boundary conditions of simulation. Increasing the value of interface heat transfer coefficient decreases the width of mushy zone.

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5

Gancarczyk, Kamil, Maciej Zubko, Aneta Hanc-Kuczkowska, Barbara Kościelniak, Robert Albrecht, Dariusz Szeliga, Maciej Motyka, Waldemar Ziaja, and Jan Sieniawski. "The Effect of Withdrawal Rate on Crystal Structure Perfection, Microstructure and Creep Resistance of Single Crystal Castings Made of CMSX-4 Nickel-Based Superalloy." Materials 12, no. 20 (October 19, 2019): 3422. http://dx.doi.org/10.3390/ma12203422.

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This study focuses on the evaluation of the crystal structure perfection in the single crystal made of CMSX-4 nickel superalloy and its effect on creep resistance. Single crystal castings were manufactured by directional solidification process at the withdrawal rate of 1, 3, 5 and 7 mm/min. Light (LM) and electron (SEM, TEM) microscopy, X-ray diffraction and Mossbauer spectroscopy were used for evaluation of the microstructure and crystal structure perfection. Castings were also subjected to creep tests. The best creep resistance was obtained for the casting manufactured at the withdrawal rate of 3 mm/min, characterized by the highest crystal structure perfection compared to the other castings examined.

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6

Angel, Nicole Marie, and Amrita Basak. "On the Fabrication of Metallic Single Crystal Turbine Blades with a Commentary on Repair via Additive Manufacturing." Journal of Manufacturing and Materials Processing 4, no. 4 (October 26, 2020): 101. http://dx.doi.org/10.3390/jmmp4040101.

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The turbine section of aircraft engines (both commercial and military) is an example of one of the most hostile environments as the components in this section typically operate at upwards of 1650 °C in the presence of corrosive and oxidative gases. The blades are at the heart of the turbine section as they extract energy from the hot gases to generate work. The turbine blades are typically fabricated using investment casting, and depending on the casting complexity, they generally display one of the three common microstructures (i.e., equiaxed or polycrystalline, directionally solidified, and single crystal). Single crystal casting is exotic as several steps of the casting process are traditionally hands-on. Due to the complex production process involving several prototyping iterations, the blade castings have a significant cost associated with them. For example, a set of 40 single crystal turbine blades costs above USD 600,000 and requires 60–90 weeks for production. Additionally, if the components suffer from material loss due to prolonged service or manufacturing defects, the traditional manufacturing methods cannot restore the parent metallurgy at the damage locations. Hence, there is a significant interest in developing additive manufacturing (AM) technologies that can repair the single crystal turbine blades. Despite the blades’ criticality in aircraft propulsion, there is currently no review article that summarizes the metallurgy, production process, failure mechanisms, and AM-based repair methods of the single crystal turbine blades. To address this existing gap, this review paper starts with a discussion on the composition of the single crystal superalloys, describes the traditional fabrication methods for the metallic single crystal turbine blades, estimates the material and energy loss when the blades are scrapped or reverted, and provides a summary of the AM technologies that are currently being investigated for their repair potential. In conclusion, based on the literature reviewed, this paper identifies new avenues for research and development approaches for advancing the fabrication and repair of single crystal turbine blades.

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7

Pan, Dong, Qing Yan Xu, and Bai Cheng Liu. "Numerical Simulation of Grain Selection Behavior of Single Crystal Ni₃Al Based Superalloy Casting." Materials Science Forum 654-656 (June 2010): 1482–85. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1482.

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Ni3Al based superalloy has recently been used for the single crystal gas turbine blade. The grain selection behavior in grain selector directly determines the casting’s final microstructure and properties. A mathematical model based on the modified CA-FD method was developed for the three-dimensional simulation of directional solidification process of Ni3Al based single crystal superalloy castings. The microstructure evolution was simulated with the modified Cellular Automaton method. The grain selection process in the grain selector and final microstructure of casting were simulated. The results indicate that the stray grain is easy to nucleate at the middle part of the pigtail because of the discontinuous mushy zones formation. This agrees with previous published experimental results. Based on simulated results, a newly designed grain selector with optimized geometry was proposed to avoid stray grains.

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8

Erickson, Gary L. "A new, third-generation, single-crystal, casting superalloy." JOM 47, no. 4 (April 1995): 36–39. http://dx.doi.org/10.1007/bf03221147.

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9

Ding, Wan Qiu. "Innovative Casting Methods for Single Crystal Turbine Blades." Materials Science Forum 1032 (May 2021): 178–85. http://dx.doi.org/10.4028/www.scientific.net/msf.1032.178.

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This report outlines a succinct analysis of the contemporary casting methods in single-crystal turbine blades. Furthermore, this paper also provides an examination of the solidification procedure in mixed turbine blades. The couple cooling and heating operation system was advanced to obtain identical thermal positions for single crystal (SC) solidification in the blade group, thereby significantly diminishing the associated flaws in the contemporary Bridgman process. The chemistry science of Nickel based alloys planed for single crystal (SC) gas turbine blades has been notably improved upon, especially when considering the initial production of alloys. The second and third production within the total operation has been enhanced by the introduction of rhenium (Re). Surged density, grain flaws, and microstructural stableness have presented themselves as significant issues within this process. Additionally, it is imperative to minimize the concentrations of the different alloying components.

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10

Kounitzky, A., J. Wortmann, and P. N. Agarwal. "A single crystal casting process for high-temperature components." Materials & Design 12, no. 6 (December 1991): 323–30. http://dx.doi.org/10.1016/0261-3069(91)90074-e.

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11

Szeliga, D., K. Kubiak, and J. Sieniawski. "Numerical Simulation of Directional Solidification Process of Single Crystal Ni- Based Superalloy Casting." Archives of Foundry Engineering 17, no. 2 (June 27, 2017): 111–18. http://dx.doi.org/10.1515/afe-2017-0061.

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Abstract The analysis of influence of mould withdrawal rate on the solidification process of CMSX-4 single crystal castings produced by Bridgman method was presented in this paper. The predicted values of temperature gradient, solidification and cooling rate, were determined at the longitudinal section of casting blade withdrawn at rate from 1 to 6mm/min using ProCAST software. It was found that the increase of withdrawal rate of ceramic mould results in the decrease of temperature gradient and the growth of cooling rate, along blade height. Based on results of solidification parameter G/R (temperature gradient/solidification rate), maximum withdrawal rate of ceramic mould (3.5 mm/min), which ensures lower susceptibility to formation process of new grain defects in single crystal, was established. It was proved that these defects can be formed in the bottom part of casting at withdrawal rate of 4 mm/min. The increase of withdrawal rate to 5 and 6 mm/min results in additional growth of susceptibility of defects formation along the whole height of airfoil.

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12

Soda, H., A. McLean, Z. Wang, and G. Motoyasu. "Pilot-scale casting of single-crystal copper wires by the Ohno continuous casting process." Journal of Materials Science 30, no. 21 (November 1995): 5438–48. http://dx.doi.org/10.1007/bf00351555.

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13

Masayuki, Nishida, Hanabusa Takao, Ayumi Shiro, and Tatsuya Matsue. "Stress Estimation of Titanium Casting Alloy by X-Ray Measurement Technique of Single Crystal." Materials Science Forum 652 (May 2010): 143–48. http://dx.doi.org/10.4028/www.scientific.net/msf.652.143.

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Residual stresses in titanium casting alloy were estimated by X-ray stress measurement technique. There are two problems in the condition of X-ray stress measurement. Firstly, the titanium casting alloy has the large crystal grains. These coarse grains were generated under solidification processes and those sizes are approximately 2 millimeter in this study. These coarse crystal grains interfere with an accurate stress measurement due to the unstable diffraction profile [1]. This is because the existence of a sufficient number of isotropic crystal grains in the X-ray irradiation area are based on the X-ray diffraction theory. In this study, the stress measurement technique of single crystal materials was adopted for the solution of this fundamental problem [2, 3]. Because the coarse crystal grain was treated as a single crystal, the high intensity diffraction profiles were observed from a certain direction with investigations of crystal orientation. The problem with the coarse crystal grain in titanium casting alloy were cleaned up by the employment of the single crystal measurement technique. Secondly, the results from this study show that the position of crystal grain within the X-ray irradiation area greatly influenced the residual stress values. Therefore, in the present paper the erasing method of this position effect was tried and discussed [4]. Finally, the improvement of the accuracy of this method for the residual stress measurement in titanium casting alloy under the several bending stresses was confirmed. These results show that the erasing method in this study is an effective correction method.

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14

Raza, Muhammad Huzaifa, Ahmad Wasim, Salman Hussain, Muhammad Sajid, and Mirza Jahanzaib. "Grain Selection and Crystal Orientation in Single-Crystal Casting: State of the Art." Crystal Research and Technology 54, no. 2 (January 4, 2019): 1800177. http://dx.doi.org/10.1002/crat.201800177.

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15

Rao, Lei, Lian Bing Zhu, and Qi Yao Hu. "Microstructure Morphology Evolution of Single Crystal Copper Rod by Ohno Continuous Casting in Copper Manufacturing System." Applied Mechanics and Materials 252 (December 2012): 360–63. http://dx.doi.org/10.4028/www.scientific.net/amm.252.360.

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Heated-mould continuous casting (Ohno continuous casting, OCC) is a kind of special continuous directional solidification technique in copper manufacturing system. Copper rod solidification process is cooperative controlled by heated mould and water cooler. Single crystal metal rod of any length can be produced by OCC. In this paper, based on continuous nucleation model, microstructure morphology evolution process of single crystal copper rod has been studied by coupled cellular automata method and finite element method. Competitive growth process has been described that tiny equiaxed crystal merged into big columnar crystals towards heat flow direction. Single crystal evolution distance changing rule has been study under different drawing speed and mould temperature by simulation and experiment results. This study provides reference for high quality single crystal copper rod in copper deep manufacturing processing.

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16

Fullagar, K. P. L., R. W. Broomfield, M. Hulands, K. Harris, G. L. Erickson, and S. L. Sikkenga. "Aero Engine Test Experience With CMSX-4® Alloy Single-Crystal Turbine Blades." Journal of Engineering for Gas Turbines and Power 118, no. 2 (April 1, 1996): 380–88. http://dx.doi.org/10.1115/1.2816600.

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A team approach involving a turbine engine company (Rolls-Royce), its single-crystal casting facilities, and a superalloy developer and ingot manufacturer (Cannon-Muskegon), utilizing the concepts of simultaneous engineering, has been used to develop CMSX-4 alloy successfully for turbine blade applications. CMSX-4 alloy is a second-generation nickel-base single-crystal superalloy containing 3 percent (wt) rhenium (Re) and 70 percent volume fraction of the coherent γ′ precipitate strengthening phase. Its finely balanced composition offers an attractive range of properties for turbine airfoil applications. In particular the alloy’s combination of high strength in relation to creep-rupture, mechanical and thermal fatigue, good phase stability following extensive high temperature, stressed exposure and oxidation, hot corrosion and coating performance, are attractive for turbine engine applications where engine performance and turbine airfoil durability are of prime importance. The paper details the single-crystal casting process and heat treatment manufacturing development for turbine blades in CMSX-4 alloy. Competitive single-crystal casting yields are being achieved in production and extensive vacuum heat treatment experience confirms CMSX-4 alloy to have a practical production solution heat treat/homogenization “window.” The creep-rupture data-base on CMSX-4 alloy now includes 325 data points from 17 heats including 3630 kg (8000 lb) production size heats. An appreciable portion of this data was machined-from-blade (MFB) properties, which indicate turbine blade component capabilities based on single-crystal casting process, component configuration, and heat treatment. The use of hot isostatic pressing (HIP) has been shown to eliminate single-crystal casting micropores, which along with the essential absence of γ/γ′ eutectic phase, carbides, stable oxide, nitride and sulfide inclusions, results in remarkably high mechanical fatigue properties, with smooth and particularly notched specimens. The Re addition has been shown not only to benefit creep and mechanical fatigue strength (with and without HIP), but also bare oxidation, hot corrosion (sulfidation), and coating performance. The high level of balanced properties determined by extensive laboratory evaluation has been confirmed during engine testing of the Rolls-Royce Pegasus turbofan.

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17

Ohno, A. "Continuous Casting of Single Crystal Ingots by the O.C.C. Process." JOM 38, no. 1 (January 1986): 14–16. http://dx.doi.org/10.1007/bf03257948.

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18

Esaka, H., K. Shinozuka, and M. Tamura. "Possible mechanism of spurious grain in single crystal casting process." International Journal of Cast Metals Research 15, no. 3 (January 2003): 297–99. http://dx.doi.org/10.1080/13640461.2003.11819500.

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19

Ma, Dexin. "Novel casting processes for single-crystal turbine blades of superalloys." Frontiers of Mechanical Engineering 13, no. 1 (November 17, 2017): 3–16. http://dx.doi.org/10.1007/s11465-018-0475-0.

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20

Guo, Yi Ping, Xiao Hui Guo, and Jun Ping Deng. "Study on the Mechanical Properties of Single Crystal Aluminum by Ohno Continuous Casting." Materials Science Forum 809-810 (December 2014): 358–62. http://dx.doi.org/10.4028/www.scientific.net/msf.809-810.358.

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In this paper, tensile properties at room temperature and bending rupture properties of single crystal aluminum wire, 4mm in diameter, fabricated by ohno continuous casting were studied, and its fracture was analyzed. The results showed that: Compared with polycrystalline aluminum samples, the yield strength of Ohno Continuous Casting single crystal aluminum changed little; Ultimate strength decreased by 42.7%; Elongation and reduction of area increased by 111.5% and 575%; Bending fatigue strength have been enhanced distinctly. Fracture of single crystal aluminum were flat tip shape, the slip line near fracture parallel to each other and uniformly distributed, the fracture is typical dimple structure and the dimple size were relatively uniform, appeared as parabolic.

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21

Kolyadov, E. V., L. I. Rassohina, E. M. Visik, V. V. Gerasimov, and E. V. Filonova. "Study of single crystal turbine blades made of ZhS32 alloy with a promising scheme of cooling." Industrial laboratory. Diagnostics of materials 84, no. 10 (October 26, 2018): 35–40. http://dx.doi.org/10.26896/1028-6861-2018-84-10-35-40.

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The results of studying single-crystal turbine blades with a promising scheme of cooling, cast from a heat-resistant ZhS32 alloy using ceramic rods with high-temperature sintering additives and additional impregnation with a varnish solution are presented. The program of crystallizing blades with a single-crystal structure is improved on a VIP-NK installation. A comparison of the operation modes of the updated program and serial technology is presented. A pilot batch of blade castings is obtained under production conditions of a machine-building enterprise with an output suitable in single-crystal structure of about 94%. Blade castings are studied using X-ray diffraction, X-ray and ultrasound methods. Quantitative metallographic analysis is carried out on an optical complex to determine spacing between axes of the first order dendrites (λ1) of the alloy and the volume fraction of the micropores in the cross section of the pen and casting lock. The results of scanning electron microscopy study of macro-and microstructure of the blade castings with a promising cooling scheme showed that the structure is typical for ZhS32alloy in the cast state and is well formed in the elements of the inner cavity of monocrystalline blades.

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22

Rzyankina, Ekaterina, Dariusz Szeliga, Nawaz Mahomed, and Andrzej Nowotnik. "Investigation of the Effect of Solidification Velocity on the Quality of Single Crystal Turbine Blades." Applied Mechanics and Materials 372 (August 2013): 54–61. http://dx.doi.org/10.4028/www.scientific.net/amm.372.54.

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The occurrence of high temperatures in combustion chambers of jet engines and gas turbines has led to the demand for new technologies and new materials for the manufacture of one of the most critical elements of these systems - the turbine blades. These elements have to withstand extreme temperatures for extended periods without loss of mechanical strength, conditions under which many alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. High temperature resistant alloys formed as single crystal (SX) structures offer the necessary material properties for safe performance under such extreme conditions. Modelling and simulation techniques were first used to study the directional solidification (DS) of crystal structures during vacuum investment casting. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this study was therefore to investigate the effect of the solidification rate on the quality of SX castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting.

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23

Kim, Eun-Hee, Hye Yeong Park, Cho-long Lee, Jong Bum Park, SeungCheol Yang, and Yeon-Gil Jung. "Single crystal casting of gas turbine blades using superior ceramic core." Journal of Materials Research and Technology 9, no. 3 (May 2020): 3348–56. http://dx.doi.org/10.1016/j.jmrt.2020.01.029.

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24

Pan, D., Q. Y. Xu, J. Yu, B. C. Liu, J. R. Li, H. L. Yuan, and H. P. Jin. "Numerical simulation of directional solidification of single crystal turbine blade casting." International Journal of Cast Metals Research 21, no. 1-4 (August 2008): 308–12. http://dx.doi.org/10.1179/136404608x362151.

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25

Inozemtsev, Aleksandr Aleksandrovich, Aleksandra Sergeevna Dubrovskaya, Konstantin Aleksandrovich Dongauzer, and Nikolay Aleksandrovich Trufanov. "Numerical Simulation for Optimizing Temperature Gradients during Single Crystal Casting Process." ISIJ International 54, no. 2 (2014): 254–58. http://dx.doi.org/10.2355/isijinternational.54.254.

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26

Albrecht, R., W. Bogdanowicz, J. Sieniawski, and K. Kubiak. "Characterization of Casting Defects in the Single Crystal Turbine Blade Airfoil." Acta Physica Polonica A 130, no. 4 (October 2016): 1091–93. http://dx.doi.org/10.12693/aphyspola.130.1091.

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27

Wang, Runnan, Qingyan Xu, Xianglin Su, Zhonglin Li, and Baicheng Liu. "Influence of gibbosity on recrystallization behavior of single crystal blade casting." Journal of Materials Processing Technology 259 (September 2018): 169–79. http://dx.doi.org/10.1016/j.jmatprotec.2018.04.036.

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28

Liu, Gang, Lin Liu, Guo Jun Zhang, and Jun Zhang. "Microstructure and Element Segregation of Ni-Base Superalloy Casting with Radiation and Liquid-Metal Cooling." Materials Science Forum 816 (April 2015): 608–12. http://dx.doi.org/10.4028/www.scientific.net/msf.816.608.

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A Re-containing single-crystal superalloy was processed with conventional radiation high rate solidification (HRS) and liquid-metal cooling (LMC) techniques, respectively. Compared with the HRS castings, LMC castings exhibited the greatly refined dendrite structures and lower segregation. At the withdrawal rate of 50 μm/s, the primary and secondary dendrite arm spacing of LMC casting was 103 and 19 μm, which were reduced by 60 % and 53 % compared to the counterpart of HRS castings. Moreover, higher withdrawal rates significantly shortened the characteristic diffusion distance and reduced the residual segregation of refractory elements after homogenization-solution treatments, which is beneficial for improving the local phase stability of Re-containing superalloys.

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29

Visik, E. M., V. V. Gerasimov, E. V. Kolyadov, and E. V. Filonova. "Features of the single crystal structure of the turbine blades made of carbon-free and carbon-containing nickel superalloys." Industrial laboratory. Diagnostics of materials 84, no. 6 (August 1, 2018): 38–43. http://dx.doi.org/10.26896/1028-6861-2018-84-6-38-42.

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A comparative study of structural features of the blade castings having a single-crystal structure and made of heat-resistant carbon-free and carbon-containing high-temperature nickel alloys upon directional crystallization with 001 crystallographic orientation is carried out. The results of the effect of directional crystallization modes on the formation of the structure and defects of castings of working blades made of carbon-containing and carbon-free high-temperature nickel alloys are presented. Changes in the degree of pickling of the near-surface layer of casting are presented as a function of pickling conditions. The microstructure of the near-surface zone of castings made of ZhS32 heat-resistant alloy is studied after different modes of their technological processing. It is shown that blade castings with a single-crystal structure made of heat-resistant carbon-free superalloys have a tendency to formation of the block structure and appearance of surface recrystallized grains. Recommendations on the use of methods of nondestructive X-ray control of blades made of carbon-frees alloys and precautions regarding birth of microporosity on the shelf and in the blade lock are specified.

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30

Yuan, C., S. Jones, P. A. Withey, and P. M. Marquis. "Development of alumina primary coat for single crystal investment casting ceramic mould." British Ceramic Transactions 101, no. 2 (May 2002): 59–64. http://dx.doi.org/10.1179/096797801225000842.

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31

Panwisawas, Chinnapat, Harshal N. Mathur, Robert W. Broomfield, Duncan Putman, Catherine M. F. Rae, and Roger C. Reed. "Prediction of recrystallisation in single crystal nickel-based superalloys during investment casting." MATEC Web of Conferences 14 (2014): 12002. http://dx.doi.org/10.1051/matecconf/20141412002.

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32

Guangji, Xu, Ding Zongfu, Ding Yutian, Kou Shengzhong, Liu Guanglin, and Li Wei. "Process parameters of manufacturing single crystal copper by heated mold continuous casting." Journal of Wuhan University of Technology-Mater. Sci. Ed. 20, no. 4 (December 2005): 100–103. http://dx.doi.org/10.1007/bf02841295.

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33

Li, Zhonglin, Jichun Xiong, Qingyan Xu, Jiarong Li, and Baicheng Liu. "Deformation and recrystallization of single crystal nickel-based superalloys during investment casting." Journal of Materials Processing Technology 217 (March 2015): 1–12. http://dx.doi.org/10.1016/j.jmatprotec.2014.10.019.

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34

Jo, Chang Yong, D. H. Kim, Yeong Seok Yoo, D. H. Ye, and Jung Hun Lee. "Effect of Boron on Solidification Microstructure in a Single Crystal Superalloy." Materials Science Forum 486-487 (June 2005): 460–63. http://dx.doi.org/10.4028/www.scientific.net/msf.486-487.460.

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Carbon and boron were mainly considered to strengthen grain boundaries formed during single crystal casting of complex shaped components. However, those elements cause segregation forming the phase with low melting temperature or with brittle nature. To determine the optimum amount of these elements, the effect of boron on solidification behavior was investigated in the C doped single crystal RR 2072 alloy. The solid/liquid interface morphologies and the solidification microstructures were studied at various solidification rates and with B addition by directional solidification.

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35

Ma, De Xin, Bin Zhou, and Andreas Bührig-Polaczek. "Development and Application of Heat-Conductor Technique for Single Crystal Components of Superalloys." Advanced Materials Research 278 (July 2011): 306–11. http://dx.doi.org/10.4028/www.scientific.net/amr.278.306.

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During single crystal (SC) solidification in turbine blades of superalloys, grain defects often form in the platform region with abrupt variation in cross-section. In order to reduce grain defects induced by component geometries, a Heat Conductor (HC) technique was developed and applied to the production of SC turbine blades. The corresponding ceramic shell moulds were produced by a modified investment casting procedure. The heat conductors with excellent heat conductivity were inserted close to the inner corners of the platform, to effectively extract the local heat during directional solidification. Both computer simulation and temperature measurements have shown that this technique is able to produce a clear improvement of the thermal condition in the critical region of the components. The SC growth in the blade body can spread into the platform more quickly before the melt at the extremity becomes deeply undercooled. Microstructure investigations reveal a remarkable reduction in grain defect formation, providing confirmation of the effectiveness of the HC technique in improving the casting quality of SC components.

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36

Liu, Chun Tao, Xiang Mei Li, Bo Wang, Zhong Ming Ren, and Jie Yu Zhang. "Effect of Simulation Conditions on Grain Selection during Solidification of Single Crystal Casting." Advanced Materials Research 146-147 (October 2010): 829–33. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.829.

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A macro-scale ProCAST and a meso-scale Cellular Automaton Finite Element model (CAFE) are used to simulate the grain selection during solidification with different simulation conditions. To improve the efficiency of the spiral grain selector, the effects of spiral geometries, boundary conditions and nucleation parameters on the grain selection are investigated. Simulation results reveal that the spiral geometries affect the height where the single crystal occurs in the spiral selector when volume nucleation is neglected. The average orientation deviation and grain number is relatively insensitive to volume nucleation and thermal boundary conditions around grain selector, and the thermal boundary conditions in the top of grain selector being of lesser importance.

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37

Zhang, Hang, Qingyan Xu, and Baicheng Liu. "Numerical Simulation and Optimization of Directional Solidification Process of Single Crystal Superalloy Casting." Materials 7, no. 3 (February 28, 2014): 1625–39. http://dx.doi.org/10.3390/ma7031625.

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38

Stanford, N. "Seeding of single crystal superalloys––role of seed melt-back on casting defects." Scripta Materialia 50, no. 1 (January 2004): 159–63. http://dx.doi.org/10.1016/j.scriptamat.2003.08.029.

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39

Esaka, H., K. Shinozuka, and M. Tamura. "Analysis of single crystal casting process taking into account the shape of pigtail." Materials Science and Engineering: A 413-414 (December 2005): 151–55. http://dx.doi.org/10.1016/j.msea.2005.08.154.

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40

Gao, S. F., L. Liu, X. B. Zhao, T. W. Huang, J. Zhang, and H. Z. Fu. "Effects of spiral geometries on grain selection during casting of single crystal superalloys." Materials Science and Technology 27, no. 12 (December 2011): 1783–87. http://dx.doi.org/10.1179/1743284711y.0000000074.

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Chen, J., W. Yan, R. G. Ding, and X. H. Fan. "Dislocation boundaries in drawn single crystal copper wires produced by Ohno continuous casting." Journal of Materials Science 44, no. 8 (April 2009): 1909–17. http://dx.doi.org/10.1007/s10853-008-3079-y.

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Wang, Ning, Lin Liu, Sifeng Gao, Xinbao Zhao, Taiwen Huang, Jun Zhang, and Hengzhi Fu. "Simulation of grain selection during single crystal casting of a Ni-base superalloy." Journal of Alloys and Compounds 586 (February 2014): 220–29. http://dx.doi.org/10.1016/j.jallcom.2013.10.036.

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43

Gao, S. F., L. Liu, N. Wang, X. B. Zhao, J. Zhang, and H. Z. Fu. "Grain Selection During Casting Ni-Base, Single-Crystal Superalloys with Spiral Grain Selector." Metallurgical and Materials Transactions A 43, no. 10 (April 11, 2012): 3767–75. http://dx.doi.org/10.1007/s11661-012-1165-x.

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Onyszko, Arkadiusz. "Gamma Prime Crystal Lattice Orientation of Turbine Blades of the Single Crystal Nickel Based CMSX-4 Superalloy." Solid State Phenomena 203-204 (June 2013): 169–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.169.

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The paper attempts to determine the changes in the γ’ lattice orientation of aircraft engine turbine blades made of the CMSX-4 single crystal nickel superalloy. The solidification of a hollow assembly structure for 2 various blades was carried out by the Bridgman method at the Research and Development Laboratory for Aerospace Materials at Rzeszow University of Technology using an ALD Vacuum Technologies vacuum furnace. Ceramic moulds made of Al2O3 were used. The alloy temperature during casting into the mould amounted to 1550°C. The specimens for Laue method tests were cut out from the blades at withdrawal rates of 3 and 4 mm/min.

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45

Zhu, Xintao, Qiang Yang, Fu Wang, and Dexin Ma. "Grain Orientation Optimization of Two-Dimensional Grain Selector during Directional Solidification of Ni-Based Superalloys." Materials 13, no. 5 (March 3, 2020): 1121. http://dx.doi.org/10.3390/ma13051121.

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The grain selection method is widely used in industry to produce Ni-based single crystal superalloys. A Z-form two-dimensional (2D) grain selector was designed to obtain high-quality single crystals. To control grain orientation deviation, one of the most important defects of the single crystal superalloys in casting, Z-form 2D grain selectors with different take-off angle were investigated in this study. The MM247LC superalloy single crystal samples were obtained by the Bridgman method modified by the Z-form grain selectors in this study. The Electron Backscattered Diffraction (EBSD) and the Optical Microscopy (OM) were used to observe and measure the grain selection growth and the microstructural evolution and orientation of the single crystal were also discussed. The results show that a Z-form 2D grain selector with an appropriate take-off angle can significantly reduce the deviation of the grain orientation. A single crystal superalloy with a deviation angle less than 6° can be obtained effectively when the take-off angle was 40°.

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46

Ma, Ning, Wentao Liu, Lili Ma, Suqin He, Hao Liu, Zhenya Zhang, Aihua Sun, Miaoming Huang, and Chengshen Zhu. "Crystal transition and thermal behavior of Nylon 12." e-Polymers 20, no. 1 (June 22, 2020): 346–52. http://dx.doi.org/10.1515/epoly-2020-0039.

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AbstractThe polyamide 12 (PA12) with different crystal forms is prepared with three crystallization paths. The crystal structures and corresponding thermal properties are systematically investigated. The results reveal that an α-form and a mixed (α + γ)-form of PA12 can be obtained by casting at 30°C and (40–80°C), respectively. Meanwhile, the γ-form of PA12 can be obtained by both casting at 90°C and slow melt cooling. However, the γ′-form is obtained only by melt quenching. Both the γ and γ′ forms of PA12 exhibit a single melting peak, whereas the α-form exhibits two melting peaks. The higher peak is attributed to the melting of γ-PA12, which originates from the melting–recrystallization of the α-PA12. It is found that the tensile properties of PA12 depend on the crystal forms. Both the γ and γ′-PA12 are strong and tough polymer materials, while α-PA12 is a strong but brittle polymer material.

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Masayuki, Nishida, Hanabusa Takao, Tatsuya Matsue, and Hiroshi Suzuki. "Neutron Stress Measurement of Coarse Crystal Grain in Aluminum Casting Alloy." Materials Science Forum 652 (May 2010): 243–48. http://dx.doi.org/10.4028/www.scientific.net/msf.652.243.

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Internal stresses in aluminum casting alloy were measured by the neutron stress measurement method with the apparatus RESA in Japan Atomic Energy Agency (JAEA). In usual cases, coarse crystal grains are included in aluminum casting alloy. These coarse crystal grains make it extremely difficult to estimate the internal stresses by the neutron diffraction [1]. The two problems arise because of the existence of the coarse crystal grains. The first problem is the production of an unstable diffraction profile in the necessary direction. The second is the edge effect which is generated by the overhang of the coarse crystal grains from the neutron irradiation area (gage volume). In this study, two kinds of new techniques used were proposed to resolve these problems. Firstly, the elastic theory based on the sin2ψ method is shown. Diffraction peaks in several directions were found by use of the rocking curve method. Following that, the lattice spaces in each principal direction were calculated from these diffraction peaks using the elastic theory. Secondly, the distribution of edge effect around the gage volume was measured using a small bit of copper single crystal. From this result, the edge effect was canceled out by the modified measurement method which was done symmetrically. Finally, the aluminum casting sample which included coarse crystal grains was set to the tensile testing machine on RESA’s measurement table and the applicability of these new techniques were confirmed experimentally.

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Watari, Koji, Kiyoshi Hirao, Manuel E. Brito, Motohiro Toriyama, and Shuzo Kanzaki. "Hot Isostatic Pressing to Increase Thermal Conductivity of Si3N4 Ceramics." Journal of Materials Research 14, no. 4 (April 1999): 1538–41. http://dx.doi.org/10.1557/jmr.1999.0206.

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Highly anisotropic Si3N4 ceramics were successfully fabricated by tape-casting of raw α–Si3N4 powders with β–Si3N4 single-crystal particles as seed particles and Y2O3 as an effective sintering aid, followed by hot isostatic pressing at a temperature of 2773 K for 2 h under a nitrogen gas pressure of 200 MPa. The microstructure consists of very large elongated grains (diameter ~10 μm; length of ~200 μm), highly oriented in the tape-casting direction. The thermal conductivity along this direction reaches 155 W m-1K-1 at room temperature, but varies significantly between room temperature and 1273 K. This thermal conductivity is closely related to (1) formation of extremely large elongated β–Si3N4 grains with a reduced amount of crystal defects due to the high-temperature firing and to (2) orientation of β–Si3N4 grains due to addition of seed particles and to tape-casting.

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Zhu, Xintao, Fu Wang, Shuaipeng Zhang, Tobias Wittenzellner, Jessica Frieß, Dexin Ma, and Andreas Bührig-Polaczek. "Using a Three-Dimensional Reduction Method in the High-Efficiency Grain Selector and Corresponding Grain Selection Mechanism." Materials 12, no. 11 (June 1, 2019): 1781. http://dx.doi.org/10.3390/ma12111781.

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In the development of a high-efficiency grain selector, the spiral selectors are widely used in Ni-based single crystal (SX) superalloys casting to produce single crystal turbine blades. For the complex three-dimensional structure of the spiral, a 2D grain selector was designed to investigate in this paper. As a result, the parameters of two-dimensional grain selection bond and the corresponding grain selection mechanism were established, and the three-dimensional grain selection bond was designed again by means of two-dimensional coupling optimization parameters.

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50

Dai, H. J., J. C. Gebelin, N. D'Souza, P. D. Brown, and H. B. Dong. "Effect of spiral shape on grain selection during casting of single crystal turbine blades." International Journal of Cast Metals Research 22, no. 1-4 (August 2009): 54–57. http://dx.doi.org/10.1179/136404609x367317.

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