Selected Article



A Study on the Environmental Embrittlement of the Ni-Si Based Intermetallic Alloys Doped with Boron and Carbon


[[abstract]]摘要 鎳矽介金屬合金(Ni3Si,有序之面心立方L12結構)為一種耐中、高溫及耐特殊酸腐蝕的材料,特別在高溫時,其優異的抗腐蝕性、抗氧化、及降伏強度隨溫度上昇而增加的特性,使其應用在高溫環境之潛力有優於其他合金;但由於該合金的常溫脆性及熱加工性相當差,以致於Ni3Si基合金目前僅可使用於低張力之鑄造零件上,如Hastelloy D.;而常溫脆性乃由於脆弱之晶界結合性所導致脆性之沿晶破裂,故若能有效增加晶界之契合性,大幅提昇其延性,當可突破其應用限制。 鎳-19矽-3鈮(Ni-19Si-3Nb)基介金屬合金,經由前人的研究結果,應用微量合金法(次元素添加量小於600ppm)以化學計量方式同時添加微量硼與碳元素,在氬氣保護下,進行電弧熔煉及墜落式鑄造成鑄塊胚料;鑄胚經以真空熱處理爐1080℃、四小時均質化與700℃、十小時時效處理後,一部份製成標距平行區3mm×2 mm×20 mm之拉伸試片,分別於大氣(14000ppm H2O vapor)真空、水氣(850ppm H2O vapor)各種氣氛下,分別進行25℃、500℃、600℃、700℃及800℃之拉伸試驗,另一部份試片則取樣進行GDS、Auger、DTA、EDS各種分析,另外藉由其金相組織、破斷面之組織,與拉伸試驗之結果比對,以探討在各種環境下影響鎳矽基合金之延性及破裂模式之主要因素。 由本實驗之結果發現,當使用微量合金法添加300ppm硼與200ppm碳於Ni-19Si-3Nb基介金屬合金時,可以有效改善水氣所引發之氫脆現象,其室溫下最大抗拉強度(UTS)由780MPa增加至1160MPa,延伸率也由5.2%提升增加到11.8%,同時亦發現添加硼與碳使其脆性轉換溫度由前人研究中的500℃提升至700℃。

[[abstract]]Abstract Intermetallic compounds based on Ni3Si (order fcc L12 structure) offer a number of interesting properties for structural applications in aggressive environments at elevated temperature. These interesting properties include the excellent corrosion and oxidation resistance at both ambient and elevated temperature, good specific strength in comparison with other materials, increasing yield strength as a function of temperature. However, binary Ni3Si, similarity the Ni3Al suffers from grain boundary embrittlement at room temperature. In addition, the Ni3Si intermetallic alloy also exhibits, brittle behavior at mid-high temperature due to the environment embrittlement. Therefore, how to improve its grain boundary adhesion and resistance of environment embrittlement will be the critical points of increasing the ductility and widespread the applications of Ni-Si intermetallic alloys. According to the pre-studies, we select the Ni-19Si-3Nb alloy as the based alloy to investigate the effect of adding boron and carbon by means of arc melting and drop casting under argon atmospheres, and then homogenizing and aging in a vacuum annealing furnace of under5×10-5 torr at 1080℃ for 4 hours and 700℃ for 10 hours respectively. The main part of heat-treated ingots where machined into the tensile test specimen with the gauge dimension of 3mm×2mm×20mm. Then the specimen where tensile test under different atmosphere, [such as air (14000ppm water vapor), vacuum (2×10-4 torr), and pure water vapor (850ppm)] at different temperature (25℃, 500℃, 600℃, 700℃, 800℃). Both of results of atmosphere-controlled tensile test, the metallography microstructure, and the fracture surface observation were summarized to investigate the effect of environment embrittlement on the ductility and fracture mode for the Ni-19Si-3Nb, and Ni-19Si-3Nb-0.15B-0.1C alloys. According to the result of this study, the microalloying of 300ppm boron and 200ppm carbon into the Ni-19Si-3Nb base alloy exhibits an effective improvement on overcoming the environment embrittlement by water vapor. The positive effect results in improving ultimate tensile strength and elongation from 780MPa, 5.2% to 1160MPa, 11.8% at room temperature in air, as well as increasing the brittle transition temperature from 500℃ to 700℃.

[[note]]參考文獻 [1] R. G. Davis and N. S. Stoloff,“Trans. TMS-AIME”, vol.233, pp.714, 1965 [2] E. M. Grala,“Mechanical Properties of Intermetallic Compounds” (Wiley, New York), pp.358, 1960 [3] T. Takasugi, M. Nagashima and 0. Izumi, “Strengthening and Ductilization of Ni3Si by the Addition of Ti Elements”, “Acta metall”, mater, vol.38, pp.747,1990 [4] T.E.Evans and A. C. Hart, Electrochem,“Acta metall”, vol.16, pp.1955, 1971 [5] K. S. Kumar and C. T. Liu,“Ordered Intermetallic Alloys”, Part II: Silicides, Trialuminides, and Others, JOM, pp.28, June 1993 [6] I. Baker and P. R. Munroe,“Improving Intermetallic Ductility and Toughness”, Journal of Metals, 28 Feb,1988 [7] A Ph.D Thesis of Chun-Huei Tsau, advised by J. w. Yeh. And J. S. C. Jang, “A Study on the Microstructure Evolution and Mechanical Behaviors of the Ni-Al-Fe Based Intermetallics”, July 1995 [8] J. S. C. Jang, S. K. Wong, P. Y. Lee,“The effect of boron on the microstructure and mechanical behavior of and Ni-19Si-3Nb based alloy”, Materials Science and Engineering, A vol.17, 2000 [9] J. S. C. Jang and C. H. Tsau,“The Effect of Niobium Additions on the Fracture ofNi-19Si-based alloys”, Materials Science and Engineering, A153 1992 [10] J. S. C. Jang, C. H. Tsau, and T.C. Tsai,“The Temperature Dependence on the Mechanical Properties of the Ni-19Si Based Alloys”, Proceedings of the 1994 Annual Conference of the Chinese Society for Materials Science, 1994 [11] J. C. Ou,“Study on the Microstructure Evolution and Mechanical Behaviors of the Ni-19Si-3Nb Based Intermetallic Alloys Doped with Boron and Carbon by using Microalloying Methods”,2000 [12] K. J. Williams,“J. Inst. Metal”, vol.97, pp.112, 1969 [13] T. Takasuhi, 0. Izumi, “Electronic and Structural Studies of Grain Boundary Strength and Fracture in L12 Ordered Alloys ON Binary A3B Alloys”“Acta Metall”, vol.33, pp.1247, 1985 [14] T.Takasuhi, 0. Izumi, and N.Masahashi, “Electronic and Structural Studies of Grain Boundary Strength and Fracture in L12 Ordered Alloys - II. on the Effect of Third Elements in Ni3Al Alloy” “Acta Metall”, vol.33, pp.1259, 1985 [15] A. I. Taub, C. L. Briant, S. C. Huang, K. M. Chang and M. R. Jackson,“Scripta Metall”, vol.20, pp.129, 1986 [16] W. C. Oliver and C. L. White,“Mater. Res. Soc. Symp”. Proc, vol.81, pp.241,1987 [17] W.C. Oliver,“Mater. Res. Soc. Symp”. Proc, vol.133, pp.397, 1989 [18] W.C. Oliver, Proc. MRS Symp,“High Temperature Ordered Intermetallic Alloys III” (edited by C. T. Liu, A. 1. Taub, N. S. Stoloff and C. C. Koch), vol.133, pp.397, 1989 [19] T. Takasugi, D. Shindo, 0. Izumi, and M. Hirabayashi,“Acta Metall”, vol.38, pp.739, 1990 [20] T. Takasugi, M. Nagashima, 0. Izumi,“Acta Metall”, vol.38, pp.747, 1990 [21] A. H. Cottrell,“Boron and Carbon in Nickel”, Iron, and Ni3Al, Materials Science and Technology, vol.7, pp.585, July 1991 [22] C. T. Liu, E. H. Lee, E. P. George, and A. J. Duncan,“Intergranular Fracture Tendency in NiAl Doped with Boron and Carbon”, skripta Metallurgica et Materialia, vol.30, pp.387-392, 1994 [23] C. T. Liu, E. P. George, W. C. Oliver,“Grain-boundary Fracture and Boron Effect in Ni3Si Alloys”,pp.77, June 1995 [24] S. K. Wang,“A study on the Microstructure Evolution and Mechanical Behaviors of the Ni-19Si-3Nb Based Intermetallic Alloys Doped with Boron or Carbon by using Microalloying Methods”, 1998 [25] C. L. Ma, T. Takasugi and S. Hanada,“ The Effect of Trapped Hydrogen on Mechaical Behavior of Ni3Si,Ti”) Intermetallic Compound, Acta Mater, vol.44, pp.1349-1359, 1996 [26] T. Takasugi, M. Nagashima, and 0. Izumi,“Acta Metall”, vol.37, pp.3425, 1989, vol.38, pp.747, 1990 [27] M. Yoshida and T. Takasud,“Philos. Mag”, A65, vol.41, 1992 [28] T. Takasugi and M. Yoshida,“J. Mater. Sci”, vol.26, pp.3032/3517, 1991 [29] T. B. Massalski, J. L. Murray, L. H. Bennett & H. Baker ASM, Metals Park ohio,“Binary Alloy Phase Diagram for Ni-Si alloy”,pp.1756, 1986 [30] T. B. Massalski, J. L. Murray, L. H. Bennett & H. Baker ASM, Metals Park ohio.“Binary Alloy Phase Diagram for Nb-Ni alloy”, pp.1682, 1986 [31] T. B. Massalski, J. L. Murray, L. H. Bennett & H. Baker ASM, Metals Park ohio.“Binary Alloy Phase Diagram for Nb-Si alloy”, pp.1696, 1986 [32] Handbook of Temary Alloy Phase Diagrams, pp.12796 [33] B. D. Cullity,“Elements of X-ray Diffraction”, Addison-Wesley, London, 2nd edition, pp.356, 1978 [34] I. Baker and E. P. George, Intermetallic Compounds:“an update, High Performance Materials, Metals and Materials”, pp.318-323, June 1992 [35] P. Nagpal and I. Baker,“Metall. Trans”, 21A pp.2281, 1990 [36] B. Schmidt, P. Nagpal and I. Baker.“Proc. MRS”, vol.133, pp.755, 1989 [37] 劉錦川、鄭憲清,“規則化介金屬化合物之最新發展”工業材料 116期,pp.56, 1996 [38]周浩森,"銲接殘留應力和變形",銲接與切割,第2卷,第一期,pp.83-92,1992 [39]A. R. Troianio, Trans.ASM, Vol.52, pp.54, 1960. [40]N. J. Petch and P. Stables, Nature, Vol.169, pp.842, 1952. [41] P. Bation and P. Azou, Proc. Of World Met. Cong., Ist. ASM, pp.535, 1951 [42] J. K. Tien, A. W. Thompson, I. M. Bemstein and R. J. Richards, “Hydrogen Transport by Dislocation”, Metall, Trans Vol.7A ,pp.821, 1976 [43] S. Van Dyck, L. Delaey, L. Froyen and L. Bekenhout,“Microstructural evolution and its influence on the mechanical properties of a nickel silicide based intermetallic alloy”, intermetallics, vol.5, pp.137-145, 1997 [44] C. L. White, R. A. Padgett, C. T. Liu and S. M. Yalisove,“Surface and Grain Boundary Segregation in Relation to Intergranular Fracture”, Boron and Sulfur in Ni3Al, Scripta Metall, vol.18, pp.1417, 1984 [45] W. C. Oliver,“ In high-temperature Ordered Intermetallic Alloys III”,MRS conf. Proc., Vol.133. Materials research Society, Pittsburgh, PP.397-402, 1989 [46] W. C. Oliver and C. L. White,“The Segregation of Boron and its Effect on the Fracture of an Ni3Si Based Alloy”, High Temperature Ordered Intermetallic Alloys II, eds. N. S. Stoloff, C. C. Koch, C. T. Liu and O. Izumi, Materials Research Society, pp.241, 1987 [47] N. Masahashi, T. Takasugi and O. Izumi,“Mechanical properties of Ni3Al Containing C, B, and Be”, Acta Metall, Vol.36, No.7, pp.1823-1830, 1988 [48] E. M. Schulson,“Proposal to Office of Basic Energy Sciences”, U.S.A, Department of Energy contract No. DEFG 02-86 ER 45260, 1990 [49] D. A. Muller, S. Subramanian, P. E. Batson, J. Silcox, and S. L. Sass, “Structure Chemistry and Bonding at Grain Boundaries in Ni3Al (1) ”: The Role of Boron in Utilizing Grain Boundaries, Acta mater,Vol.44, No.4, pp.1637-1645, 1996 [50] C. T. Liu, C.L. White and J. A. Horton, “Effect of Boron on Grain-boundaries in Ni3Al” “Acta metall”, vol.3, pp.3213, 1985 [51] E. P. George, C. T. Liu and D. P. Pope, “Fracture in Ni3Al Environmental and Dopant Effects”, “Scripta Metall. Mater”, vol.30, pp.37, 1994 [52] C. T. Liu,“Structural Intermetallics-Proceedings”(edited by R. Darolia et al.), TMS, Warrendale, PA 365, 1993 [53] C. T. Liu,“Scripta metall”, mater, vol.27, pp.25, 1992 [54] J. E. Harris, J. A. Whiteman, and A. G. Quarrell,“Steels for reactor pressure circuits”, The Iron and Steel Institute, London, pp.54, 1961 [55] R. D. Noebe, C. L. Cullers, and R. R. Bowman,“J. Mater. Res”, vol.7 pp.605, 1992 [56] C. Y. Ma, T. Parthasarathy, P. G. Shewmon, W. Gust and R. A. Foumelle, “Scripta Metall. Mater”, pp.1235, 1992 [57] J. E. Hack, J. M. Brzeski, and R. Darolia, “Evidence of Inherent Ductility In Single Crystals of the Ordered Intermetallic Compound NiAl”, “Scr. Metall”, vol.27, pp.1259, 1992 [58] L. Liu, F. Sommer and H. Z. Fu,“Effect of Solidification Conditions on MC Carbides in a Nickel Base Superalloy IN 738LC”, Scripta Metall. et Mater, vol.30, pp.587-591, printed in U.S.A, 1994 [59] R. D. K. Misra and P. Rama Rao,“Grain Boundary Segregation Isotherms”, Materials Science and Technology, vol.13, pp.277, April 1997 [60] J S. C. Jang, S. K. Wong, and G. Y. Chen,“The effect of Heat-treatment on the Microstructure and Mechanical Properties of the Ni-19Si-3Nb-0.15B Intermetallic Alloy”, 中國材料科學學會87年年會論文集, pp.21, 1998 [61] J. Phys. Chem. Ref. Data, vol. 14, Suppl. 1, 1985 [62] Richard A. Swalin, “Thermodynamics of Solid”, Eurasia Book Co., Print in the United States of America , pp.116, 1962 [63] 金重勳, “熱處理”,復文書局,台灣, pp.47, 1994