国内图书分类号：TB332 学校代码：10213 国际图书分类号：666 密级：公开
工学硕士学位论文
硕士研究生：张蕾
导 师：叶枫教授
申请学位：工学硕士
通讯加密
学科：材料学
所在单位：材料科学与工程学院互联互通软件
答辩日期：2010年7月
授予学位单位：哈尔滨工业大学
Classified Index: TB332
U.D.C.: 666
Dissertation for the Master Degree in Engineering
HIGH TEMPERATURE COMPRESSIVE DEFORMATION OF SILICON NITRIDE AND CARBIDE CERAMIC COMPOSITES
Candidate：Zhang Lei
Supervisor：Prof. Ye Feng
Academic Degree Applied for：Master of Engineering Speciality：Materials Science Affiliation：School of Mater. Sci. & Eng. Date of Defence：July, 2010
Degree-Conferring-Institution：Harbin Institute of Technology
哈尔滨工业大学工学硕士学位论文
摘要
小型净水器本文采用放电等离子烧结(SPS)法制备了致密的BAS/Si3N4复合材料、SiAlON陶瓷和BAS/SiC复合材料，并在SPS设备中研究了以上材料的高温压缩变形行为，并讨论了压缩变形对材料组织与性能的影响规律。
不同BAS含量的Si3N4复合陶瓷，约在1580℃时开始产生压缩变形，随着材料中所含BAS的量增多，能够在较低的温度下实现较快的压缩变形，最大压缩变形速率在10-3s-1量级。其中40wt%BAS/Si3N4材料1600℃最大应变速率能达到 1.5×10-2s-1，已进入了超塑性变形的范畴。压缩后材料中的长棒状β-Si3N4晶粒沿垂直于外力方向的平面择优分布。 不同稀土掺杂的5wt%BAS/RE-α-SiAlON陶瓷在1500℃时已开始产生压缩变形，到达1630℃后能产生最大应变速率，也在10-3s-1量级上。材料的变形能力与其中所含的晶间相团聚相关，其中Yb-SiAlON材料晶间相分布更均匀，从而应变量与应变速率均最小。材料压缩前后组织形貌无明显变化，长棒状α-SiAlON晶粒在压缩过程中转动和滑移是实现材料宏观应变的主要原因。而添加了过量稀土氧化物的Y1010-α-SiAlON陶瓷同样均在1630℃附近实现了最大压缩变形速率。其中材料的压缩变形量和变形速率与所添加的助烧剂的量成正比关系。对Y1010E2材料而言，材料中的晶间相含量很少，未能实现宏观可见的应变。压缩过程中，同时伴随着晶粒的转动和长大，压缩后的Y1010E4和Y1010E6材料中的长棒状α-Si3N4晶粒在直径和长度方向上均有生长。
不同BAS含量的SiC复合陶瓷约在1590℃时变形启动，同时伴有一个较小的极大压缩变形速率。在进入1600℃的保温阶段时，40wt%BAS/SiC 的压缩变形速率能达到 6.1×10-3s-1。由于BAS/SiC中主要含有等轴状的α-SiC晶粒，压缩后材料并未产生各向异性。同时，尽管α-SiC晶粒的尺寸较大，在几个微米以上，因为等轴状的晶粒在粘性液相中的移动更容易实现，其压缩变形能力仍大于含有细小长棒状晶粒的BAS/Si3N4材料。
关键词Si3N4基陶瓷；SiC基陶瓷；放电等离子烧结(SPS)；高温压缩变形
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哈尔滨工业大学工学硕士学位论文
Abstract
微型汽油机
Dense BAS/Si3N4 composites, SiAlON ceramics, and BAS/SiC composites were fabricated by spark plasma sintering (SPS). The high temperature compressive deformation behaviour and its effects on the microstructures and mechanical were studied.
Si3N4 composites containing different amount of BAS started to deform at about 1580℃. As the BAS content increases, a faster compressive deformation with a maximum compressive strain rate o
n the order of 10-3s-1 were achieved at lower temperature (1600℃). The 40wt%BAS/Si3N4 composite exhibited a maximum strain rate of 1.5×10-2s-1 when deformed under 1600℃ for 5min. This high strain rate demonstrates superplasticity. Texturing of the elongated β-Si3N4 grains, which tended to align along the surface perpendicular to the uniaxial pressure, was observed.
5wt%BAS/RE-α-SiAlONs doped with different rare-earth ions began deformation at 1500℃, and achieved a maximum strain rate of 10-3s-1 at 1630℃, although much less BAS phase was present. The deformation capability of the materials was related to the amount of the interface phases. Yb-SiAlON had a much clearer interface, hence lesser strain and slower strain rate. The strain of the material was accomplished by rotation and sliding of elongated α-SiAlON grains through the deformation process. No significant difference in microstructures before and after deformation has been observed.
Y1010-α-SiAlON using extra rare-earth oxides as the sinter additive also achieved a remarkable compressive strain rate. The maximum reached 10-3s-1 at 1630℃. The compressive deforming directly related with the contents of the sintering additives. Both the rotation and growth of elongated α-SiAlON grains contributed to the deformation process, resulting in larger grain size as well as larger aspect ratio.
SiC composite containing different amount of BAS started deforming at 1590℃. 40wt%BAS/SiC reached maximum compressive deformative rate of 6.1×10-3s-1 at 1600℃. Due to the equiaxed α-SiC grains within the composite, no anisotropy were developed. The equiaxed α-SiC grains had less resistance when
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哈尔滨工业大学工学硕士学位论文
moving in the viscous liquid formed at the high temperatures, and the materials showed a better compressive deformation capability in comparison with BAS/Si3N4 composites, in spite of the much larger micron grain sizes.
Keywords Si3N4 based ceramics, SiC based ceramics, spark plasma sintering (SPS), high temperature compressive deformation
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