预烧结氧化铝坯体的强度模型及微细加工特性
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摘要
陶瓷材料因其优良的物理化学性能,在微机电系统、微零件和微结构中具有广泛的应用需求。结合微细刀具在线制作和陶瓷预烧结体加工,可以较快地加工出陶瓷微细结构。其中,预烧结可提高坯体强度,有利于减小微细加工对象的边缘破损,但强度过高将加剧刀具磨损。目前对陶瓷预烧结体强度随预烧结条件的变化规律尚未完全明了,急需针对微细加工特点设计合理的预烧结体强度。
对于陶瓷粉末压坯的烧结,烧结温度和烧结时间对颗粒间烧结颈的生长有着重要影响,而烧结颈的大小又决定着陶瓷坯体的强度变化。
本文对氧化铝生坯进行了不同温度和不同时间下的预烧结,并参照三点弯曲法对得到的预烧结体(坯体)进行强度测试；同时对颗粒间的烧结颈进行了理论估算,借鉴粉末冶金中的强度模型预测了陶瓷预烧结体的强度。从抗弯强度测试结果可以看出,坯体强度随着预烧结温度的增加几乎呈指数关系而快速增加,但随着预烧结时间的增加却增加缓慢；根据强度理论预测的结果,实测值和预测值的变化趋势完全一致,且相符程度较好。从而在理论上建立了坯体强度与预烧结温度和时间的关系,为微细加工中坯体强度的设计和预烧结条件的合理选择奠定了理论基础。
陶瓷微细加工中,坯体强度的大小直接影响边缘质量和刀具磨损,刀具磨损则直接影响微结构的尺寸精度,所以坯体强度的合理设计对于微细加工非常重要。
本文结合不同加工参数下的试验探索,对不同强度的预烧结坯体进行了微细长槽加工,通过定量表征微细结构的边缘破损尺寸以及刀具轴向磨损量和其端部形状变化程度等,确定了坯体预烧结强度对边缘破损程度和刀具磨损的影响规律,为在微细加工中优化选择坯体的预烧结强度提供了依据。
通过实际加工实验证实,在本文实验条件下,如果综合考虑边缘质量和刀具磨损,坯体强度以7.302-9.404MPa为好,且走刀速度不宜过小,主轴转速越小越好。其中,选择上限有利于提高微细结构的边缘质量,且走刀速度越小越好；选择下限,则可提高预烧结体的制备效率,同时减小加工过程中的刀具磨损。
所有研究结果表明,综合考虑加工条件、以及坯体预烧结强度对边缘破损和刀具磨损程度的影响,对强度进行优化选择,进而通过坯体强度理论预测模型合理设计预烧结工艺,进而获得理想的坯体强度,是提高陶瓷微细加工质量和效率的有效方法。
Ceramics is widely used in micro components and micro features because of its excellent properties such as resistance to erosion and high temperature. Ceramic micro structure can be easily processed by machining pre-sintered compact. In the machining process, the strength of pre-sintered compact has a significant impact on edge quality and tool wear. However, the relationship between compact strength and pre-sintering condition is not clear. It is also necessary to select the optimal strength of pre-sintered alumina for micro machining.
Pre-sintering temperature and time are key factors that affect the strength of ceramic compact by controlling the growth of sintering neck between particles. In this paper, alumina green compacts were pre-sintered, and then three-point flexure strength tests were carried out. Meanwhile, the theoretical strength of pre-sintered compact was obtained by calculating the size of sintering neck. From experimental results, it can be seen that strength is an exponential function of pre-sintering temperature and is also a logarithmic function of pre-sintering time approximately. And theoretical strengths match well with the experimental values. Therefore the model and be used to select the proper strength and its pre-sintering condition.
In micro-machining, the edge quality of machined micro features and tool wear are directly influenced by the strength of alumina. In this paper, experiments of under different machining parameters and strength were carried out. The evaluation parameters such as damage extent of edge length, width of edge damage, length of tool wear and shape change of tool end was also been established. And the relationship between evaluation parameters and strength provides a basis for optimal selection of strength. The experimental results show that7.302-9.404MPa is the proper choice when both edge quality and tool wear are taken as the evaluation parameters. The higher strength will improve edge quality. And the lower strength will improve the efficiency of preparing pre-sintered alumina and reduce the tool wear.
In summary, it is an effective way to improve the machining equality and efficiency that optimizing pre-sintering conditions and strength selection, which are respectively based on the theoretical prediction model and the relationship between strength and evaluation parameters.
对于陶瓷粉末压坯的烧结,烧结温度和烧结时间对颗粒间烧结颈的生长有着重要影响,而烧结颈的大小又决定着陶瓷坯体的强度变化。
本文对氧化铝生坯进行了不同温度和不同时间下的预烧结,并参照三点弯曲法对得到的预烧结体(坯体)进行强度测试；同时对颗粒间的烧结颈进行了理论估算,借鉴粉末冶金中的强度模型预测了陶瓷预烧结体的强度。从抗弯强度测试结果可以看出,坯体强度随着预烧结温度的增加几乎呈指数关系而快速增加,但随着预烧结时间的增加却增加缓慢；根据强度理论预测的结果,实测值和预测值的变化趋势完全一致,且相符程度较好。从而在理论上建立了坯体强度与预烧结温度和时间的关系,为微细加工中坯体强度的设计和预烧结条件的合理选择奠定了理论基础。
陶瓷微细加工中,坯体强度的大小直接影响边缘质量和刀具磨损,刀具磨损则直接影响微结构的尺寸精度,所以坯体强度的合理设计对于微细加工非常重要。
本文结合不同加工参数下的试验探索,对不同强度的预烧结坯体进行了微细长槽加工,通过定量表征微细结构的边缘破损尺寸以及刀具轴向磨损量和其端部形状变化程度等,确定了坯体预烧结强度对边缘破损程度和刀具磨损的影响规律,为在微细加工中优化选择坯体的预烧结强度提供了依据。
通过实际加工实验证实,在本文实验条件下,如果综合考虑边缘质量和刀具磨损,坯体强度以7.302-9.404MPa为好,且走刀速度不宜过小,主轴转速越小越好。其中,选择上限有利于提高微细结构的边缘质量,且走刀速度越小越好；选择下限,则可提高预烧结体的制备效率,同时减小加工过程中的刀具磨损。
所有研究结果表明,综合考虑加工条件、以及坯体预烧结强度对边缘破损和刀具磨损程度的影响,对强度进行优化选择,进而通过坯体强度理论预测模型合理设计预烧结工艺,进而获得理想的坯体强度,是提高陶瓷微细加工质量和效率的有效方法。
Ceramics is widely used in micro components and micro features because of its excellent properties such as resistance to erosion and high temperature. Ceramic micro structure can be easily processed by machining pre-sintered compact. In the machining process, the strength of pre-sintered compact has a significant impact on edge quality and tool wear. However, the relationship between compact strength and pre-sintering condition is not clear. It is also necessary to select the optimal strength of pre-sintered alumina for micro machining.
Pre-sintering temperature and time are key factors that affect the strength of ceramic compact by controlling the growth of sintering neck between particles. In this paper, alumina green compacts were pre-sintered, and then three-point flexure strength tests were carried out. Meanwhile, the theoretical strength of pre-sintered compact was obtained by calculating the size of sintering neck. From experimental results, it can be seen that strength is an exponential function of pre-sintering temperature and is also a logarithmic function of pre-sintering time approximately. And theoretical strengths match well with the experimental values. Therefore the model and be used to select the proper strength and its pre-sintering condition.
In micro-machining, the edge quality of machined micro features and tool wear are directly influenced by the strength of alumina. In this paper, experiments of under different machining parameters and strength were carried out. The evaluation parameters such as damage extent of edge length, width of edge damage, length of tool wear and shape change of tool end was also been established. And the relationship between evaluation parameters and strength provides a basis for optimal selection of strength. The experimental results show that7.302-9.404MPa is the proper choice when both edge quality and tool wear are taken as the evaluation parameters. The higher strength will improve edge quality. And the lower strength will improve the efficiency of preparing pre-sintered alumina and reduce the tool wear.
In summary, it is an effective way to improve the machining equality and efficiency that optimizing pre-sintering conditions and strength selection, which are respectively based on the theoretical prediction model and the relationship between strength and evaluation parameters.
引文
[1]金鹏,谭久斌.基于UV—LIGA技术的微型火箭及微型动力系统技术[J].中国机械工程,2005(14)：1233-1234.
[2]BAUER W, KNITTER R. Development of a rapid prototyping process chain for the production of ceramic microcomponents [J]. Journal of Materials Science,2002, 37(15):3127-3140.
[3]LIN H C, KANG S, PRINZ F B, et al.26th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures. Cocoa Beach, Florida,2002 [C].
[4]CHRISTIAN, KENIS P J A. Fabrication of Ceramic Microscale Structures [J]. Journal of the American Ceramic Society,2007,90(9):2779-2783.
[5]WANG J, LIU G, XIONG Y, et al. Fabrication of ceramic microcomponents and microreactor for the steam reforming of ethanol [J]. Microsystem Technologies,2008, 14(9-11):1245-1249.
[6]FENG J, KIM B S, SHIH A, et al. Tool wear monitoring for micro-end grinding of ceramic materials [J]. Journal of Materials Processing Technology,2009,209(11): 5110-5116.
[7]PERRIEA W, RUSHTONA A, GILL M, et al. Femtosecond laser micro-structuring of alumina ceramic [J]. Applied Surface Science,2005,248(1-4):213-217.
[8]YANG Y, LI X C. ASME 2003 International Mechanical Engineering Congress and Exposition. Washington, DC, USA,2003 [C].
[9]MAIER H R, MICHAELI N. Green Machining of Alumina [J]. Key Engineering Materials, 1997,132-136:436-439.
[10]JANOSOVITS U, GROTHE A, POHLMANN H J, et al. Improvement of the green machining process of Si3N4 [J]. Ceramic Forum International/Ber. DKG,1999,76(5):24-28.
[11]SU B, DHARA S, WANG L. Green ceramic machining:A top-down approach for the rapid fabrication of complex-shaped ceramics [J]. Journal of the European Ceramic Society, 2008,28(11):2109-2115.
[12]LI J Z, WU T, YU Z Y, et al. The 5th International Conference on MicroManufacturing, Madison, Wisconsin, USA,2010 [C].
[13]DHARA S, SU B. Green Machining to Net Shape Alumina Ceramics Prepared Using Different Processing Routes [J]. International Journal of Applied Ceramic Technology,2005,2(3):262-270.
[14]LEE D G, LEE H G, KIM P J, et al. Micro-drilling of alumina green bodies with diamond grit abrasive micro-drills [J]. International Journal of Machine Tools & Manufacture,2003,43(6):551-558.
[15]SONG J H, EVANS J R G. On the Machinability of Ceramic Compacts [J]. Journal of the European Ceramic Society,1997,17(14):1665-1673.
[16]吴涛.陶瓷微细结构的生坯加工方法研究[D]：(硕士学位论文).大连：大连理工大学,2010.
[17]YAN B H, HUANG F Y, CHOW H M. Study on the turning characteristics of alumina-based ceramics [J]. Journal of Materials Processing Technology,1995,54(1-4):341-347.
[18]SHIN H W, WON P, KOK C K, et al. Machining Channels on Mesoscale Ceramic Components [J]. Journal of Manufacturing Processes,2004,6(1):15-23.
[19]周玉,葛启录,杨乐民,等.一种新的陶瓷加工工艺——两次烧结中间加工法[J].兵器材料科学与工程,1990(10)：41-46.
[20]黄慧,李静,张富强,等.成型压力和预烧结温度对氧化锆陶瓷可加工性能的影响[J].华西口腔医学杂志,2011,29(5)：534-536.
[21]SCHELLER Il W L. Conventional Machining of Green Aluminum/Aluminum Nitride Ceramics [J]. The Ohio Journal of Science,1994,94(5):151-154.
[22]FILSER F T. Direct Ceramic Machining of Ceramic Dental Restorations [D]. Zurich: Swiss Federal Institute of Technology Zurich,2001.
[23]FILSER F, KOCHER P, GAUCKLER L J. Net-shaping of ceramic components by direct ceramic machining [J]. Assembly Automation,2003,23(4):382-390.
[24]YIN L, PENG H X, YANG L, et al. Fabrication of three-dimensional inter-connective porous ceramics via ceramic Green machining and bonding [J]. Journal of the European Ceramic Society,2008,28(3):531-537.
[25]王昕,田进涛.先进陶瓷制备工艺[M].北京：化学工业出版社,2009.
[26]果世驹.粉末烧结理论[M].北京：冶金工业出版社,1998.
[27]HARDY D, GREEN D J. Mechanical Properties of a Partially Sintered Alumina [J]. Journal of the European Ceramic Society,1995,15(8):769-775.
[28]WILCOX P D, CUTLER I B. Strength of Partly Sintered Alumina Compacts [J]. Journal of the American Ceramic Society,1966,49(5):249-252.
[29]NYCE A C, SHAFER W M. Relationship of B. E. T. Surface Area to the Sintering Behavior of Spherical Copper Particles [J]. International Journal of Powder Metallurgy,1972, 8(4):171-180.
[30]XU X P, LU P Z, GERMAN R M. Densification and strength evolution in solid-state sintering:Part II Strength model [J]. Journal of Materials Science,2002,37(1): 117-126.
[31]尹衍升,张景德.氧化铝陶瓷及其复合材料[M].北京：化学工业出版社,2001.
[32]KUCZYNSKI G C. Self-diffusion in sintering of metallic particles [J]. Trans. AIME, 1949,185:169-178.
[33]KRASULIN Y L, TIMOFEEV V N, BARINOV S M, et al. Strength and fracture of porous ceramic sintered from spherical particles [J]. Journal of Materials Science,1980, 15(6):1402-1406.
[34]WRIGHT J K. The Effect of Firing Conditions on the Strength of Hematite compacts [J]. Powder Technology,1976,14(1):103-113.
[35]XU X P, YI W W, GERMAN R M. Densif ication and strength evolution in solid-state sintering:Part I Experimental investigation [J]. Journal of Materials Science, 2002,37(3):567-575.
[36]PROCHAZKA S, COBLE R L. Surface Diffusion in the Initial Sintering of Alumina, Part III Kinetic study [J]. Physic of Sintering,1970,2(2):15-33.
[37]LIN F J T, JONGHE L C D. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique [J]. Journal of the American Ceramic Society,1997,80(9): 2269-2277.
[38]张锐.陶瓷工艺学[M].北京：化学工业出版社,2007.
[39]中国国家标准化管理委员会.GB/T 6569-2006精细陶瓷弯曲强度试验方法[S].
[40]GERMAN R M:Sintering Theory and Practice [M]. New York:Wiley-Interscience,1996.
[41]宋久鹏,柳葆生.氧化铝陶瓷粉末固相烧结过程模拟[J].西南交通大学学报,2008,43(2)：275-279.
[2]BAUER W, KNITTER R. Development of a rapid prototyping process chain for the production of ceramic microcomponents [J]. Journal of Materials Science,2002, 37(15):3127-3140.
[3]LIN H C, KANG S, PRINZ F B, et al.26th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures. Cocoa Beach, Florida,2002 [C].
[4]CHRISTIAN, KENIS P J A. Fabrication of Ceramic Microscale Structures [J]. Journal of the American Ceramic Society,2007,90(9):2779-2783.
[5]WANG J, LIU G, XIONG Y, et al. Fabrication of ceramic microcomponents and microreactor for the steam reforming of ethanol [J]. Microsystem Technologies,2008, 14(9-11):1245-1249.
[6]FENG J, KIM B S, SHIH A, et al. Tool wear monitoring for micro-end grinding of ceramic materials [J]. Journal of Materials Processing Technology,2009,209(11): 5110-5116.
[7]PERRIEA W, RUSHTONA A, GILL M, et al. Femtosecond laser micro-structuring of alumina ceramic [J]. Applied Surface Science,2005,248(1-4):213-217.
[8]YANG Y, LI X C. ASME 2003 International Mechanical Engineering Congress and Exposition. Washington, DC, USA,2003 [C].
[9]MAIER H R, MICHAELI N. Green Machining of Alumina [J]. Key Engineering Materials, 1997,132-136:436-439.
[10]JANOSOVITS U, GROTHE A, POHLMANN H J, et al. Improvement of the green machining process of Si3N4 [J]. Ceramic Forum International/Ber. DKG,1999,76(5):24-28.
[11]SU B, DHARA S, WANG L. Green ceramic machining:A top-down approach for the rapid fabrication of complex-shaped ceramics [J]. Journal of the European Ceramic Society, 2008,28(11):2109-2115.
[12]LI J Z, WU T, YU Z Y, et al. The 5th International Conference on MicroManufacturing, Madison, Wisconsin, USA,2010 [C].
[13]DHARA S, SU B. Green Machining to Net Shape Alumina Ceramics Prepared Using Different Processing Routes [J]. International Journal of Applied Ceramic Technology,2005,2(3):262-270.
[14]LEE D G, LEE H G, KIM P J, et al. Micro-drilling of alumina green bodies with diamond grit abrasive micro-drills [J]. International Journal of Machine Tools & Manufacture,2003,43(6):551-558.
[15]SONG J H, EVANS J R G. On the Machinability of Ceramic Compacts [J]. Journal of the European Ceramic Society,1997,17(14):1665-1673.
[16]吴涛.陶瓷微细结构的生坯加工方法研究[D]：(硕士学位论文).大连：大连理工大学,2010.
[17]YAN B H, HUANG F Y, CHOW H M. Study on the turning characteristics of alumina-based ceramics [J]. Journal of Materials Processing Technology,1995,54(1-4):341-347.
[18]SHIN H W, WON P, KOK C K, et al. Machining Channels on Mesoscale Ceramic Components [J]. Journal of Manufacturing Processes,2004,6(1):15-23.
[19]周玉,葛启录,杨乐民,等.一种新的陶瓷加工工艺——两次烧结中间加工法[J].兵器材料科学与工程,1990(10)：41-46.
[20]黄慧,李静,张富强,等.成型压力和预烧结温度对氧化锆陶瓷可加工性能的影响[J].华西口腔医学杂志,2011,29(5)：534-536.
[21]SCHELLER Il W L. Conventional Machining of Green Aluminum/Aluminum Nitride Ceramics [J]. The Ohio Journal of Science,1994,94(5):151-154.
[22]FILSER F T. Direct Ceramic Machining of Ceramic Dental Restorations [D]. Zurich: Swiss Federal Institute of Technology Zurich,2001.
[23]FILSER F, KOCHER P, GAUCKLER L J. Net-shaping of ceramic components by direct ceramic machining [J]. Assembly Automation,2003,23(4):382-390.
[24]YIN L, PENG H X, YANG L, et al. Fabrication of three-dimensional inter-connective porous ceramics via ceramic Green machining and bonding [J]. Journal of the European Ceramic Society,2008,28(3):531-537.
[25]王昕,田进涛.先进陶瓷制备工艺[M].北京：化学工业出版社,2009.
[26]果世驹.粉末烧结理论[M].北京：冶金工业出版社,1998.
[27]HARDY D, GREEN D J. Mechanical Properties of a Partially Sintered Alumina [J]. Journal of the European Ceramic Society,1995,15(8):769-775.
[28]WILCOX P D, CUTLER I B. Strength of Partly Sintered Alumina Compacts [J]. Journal of the American Ceramic Society,1966,49(5):249-252.
[29]NYCE A C, SHAFER W M. Relationship of B. E. T. Surface Area to the Sintering Behavior of Spherical Copper Particles [J]. International Journal of Powder Metallurgy,1972, 8(4):171-180.
[30]XU X P, LU P Z, GERMAN R M. Densification and strength evolution in solid-state sintering:Part II Strength model [J]. Journal of Materials Science,2002,37(1): 117-126.
[31]尹衍升,张景德.氧化铝陶瓷及其复合材料[M].北京：化学工业出版社,2001.
[32]KUCZYNSKI G C. Self-diffusion in sintering of metallic particles [J]. Trans. AIME, 1949,185:169-178.
[33]KRASULIN Y L, TIMOFEEV V N, BARINOV S M, et al. Strength and fracture of porous ceramic sintered from spherical particles [J]. Journal of Materials Science,1980, 15(6):1402-1406.
[34]WRIGHT J K. The Effect of Firing Conditions on the Strength of Hematite compacts [J]. Powder Technology,1976,14(1):103-113.
[35]XU X P, YI W W, GERMAN R M. Densif ication and strength evolution in solid-state sintering:Part I Experimental investigation [J]. Journal of Materials Science, 2002,37(3):567-575.
[36]PROCHAZKA S, COBLE R L. Surface Diffusion in the Initial Sintering of Alumina, Part III Kinetic study [J]. Physic of Sintering,1970,2(2):15-33.
[37]LIN F J T, JONGHE L C D. Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique [J]. Journal of the American Ceramic Society,1997,80(9): 2269-2277.
[38]张锐.陶瓷工艺学[M].北京：化学工业出版社,2007.
[39]中国国家标准化管理委员会.GB/T 6569-2006精细陶瓷弯曲强度试验方法[S].
[40]GERMAN R M:Sintering Theory and Practice [M]. New York:Wiley-Interscience,1996.
[41]宋久鹏,柳葆生.氧化铝陶瓷粉末固相烧结过程模拟[J].西南交通大学学报,2008,43(2)：275-279.