Ning ZHANG
,
Hongqiang RU
,
Xudong SUN
,
Qingkui CAI
材料科学技术（英文）
The α-SiC in 0.5μm size powders were coated with Al2O3 and Y2O3 by a coprecipitation coating (CPC) method for fabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechanical mixing (MM) method for comparison. Two kinds of SiC/YAG composites were manufactured by pressureless sintering using the different powders, named CPC composite and MM composite thereafter respectively. It is shown that the CPC composite has the advantages of homogeneous distribution of YAG phase and of being sintered to high density at a low temperature, 100℃ lower than that of MM composite. The strength (573 MPa) and hardness (23.3 GPa) of the CPC composite are significantly higher than those (323 MPa and 13.5 GPa) of the MM composite, respectively.
关键词:
Coprecipitation
,
null
,
null
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
,
K.A.Khalil
材料科学技术（英文）
Alumina-(0 similar to 20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed-alumina and iron powders at 1400 degreesC and 30 MPa for 30 min. Hot-pressed bodies with nearly theoretical density were obtained for addition up to 10 vol. pct Fe, but relative density decreased gradually with further increase in Fe addition. The materials exhibit a homogeneous dispersion of Fe. Fracture strength of the composites exhibits a maximum value of 604 MPa at 15 vol. pct Fe, which is 1.5 times that of alumina alone. Fracture toughness increases with the increase in Fe content, reaching 7.5 MPa.m(1/2) at 20 vol. pct Fe. The theoretical values of fracture toughness was calculated and compared with the experimental one. Toughening mechanisms of the composites are also discussed.
关键词:
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
材料科学技术（英文）
Thermal shock behaviour was investigated for two morphologically different composites comprising an alumina matrix and 20 vol. pct Fe particles for a wide range of quenching temperature differences (∆T=100~800°C) and compared to a monolithic alumina. The retained strength and critical quenching temperature difference, ∆Tc, of the two composites were a significant improvement over the values for the respective monolithic alumina. Crack lengths and densities were shown to be greater for the alumina than for the two composites at all quenching temperature differences. The thermal shock resistance parameters for monolithic alumina and the two composites were calculated according to their mechanical and physical properties. The calculated results agree well with the experimental one and indicate possible explanations for the differences in thermal shock behaviour.
关键词:
Alumina-iron composite
,
null
,
null
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
材料科学技术（英文）
Two morphologically different composites comprising an alumina matrix and 20 vol. pct Fe particles have been fabricated by hot pressing technique. Two kinds of microstructures, i.e. a dispersive distribution of Fe particles and a network distribution of Fe particles in alumina matrix, have been produced. Both composites are tougher than the virgin alumina matrix. The fracture toughness of the composite with a network microstructure is much higher than the composite with a microstructure of dispersed particles. For the particulate dispersion microstructure, the main limitation to the toughening is the lack of plastic deformation of the ductile Fe due to the pull out of Fe particles, indicating weak bonding at the Al2O3/Fe interface. For the network microstructure composite, the gauge length of the ductile phase is much larger, allowing the ductile Fe to be stretched to failure between the crack faces. The weak bonding at Al2O3/Fe interface can promote partial debonding and contribute further to toughening in the network microstructure composite.
关键词:
周镇
,
艾育华
,
孔文俊
工程热物理学报
本文利用双腔泄压式定压燃烧弹,研究了高压下典型IGCC合成气的层流火焰传播特性,得到了不同压力(0.1～1 MPa)和不同当量比下(0.6～3.0)合成气的层流火焰传播速度和Markstein长度.实验结果表明,层流火焰传播速度随当量比先增加后减少,随压力的增加而减小.Davis和Sun机理能较好地预测高压下合成气层流火焰的传播速度.Markstein长度随当量比的增加而增加,随压力的增加而减小.
关键词:
合成气
,
球形火焰
,
层流火焰传播速度
,
Markstein长度
程杰锋
,
唐广波
,
刘正东
钢铁研究学报
选取了现有典型的C-Mn钢相变过程的物理冶金模型,包括5组孕育期模型、7组相变动力学方程模型、5组相变后铁素体晶粒尺寸模型.利用自行开发的组织性能预报系统软件模拟计算了在3组实际冷却工艺条件下各模型的奥氏体转变过程,并对各模型进行了评价.结果表明,对于所设定的成分和工艺条件,适用性较好的孕育期模型是Kwon所提出的模型;适用性较好的动力学方程模型是Liu、Donnay和Sun所提出的模型;适用性较好的铁索体晶粒尺寸模型是Hodgson所提出的模型.
关键词:
孕育期
,
相变
,
适用性分析
朱亮
,
肖毅
复合材料学报
为满足在工程应用中对建立拉压性能不同纤维增强复合材料的非线性本构理论的需要,考虑静水压影响的Drucker-Prager屈服准则与各向异性的Hill屈服准则相结合,提出了广义Hill屈服准则,并推广到Sun-Chen的单参数塑性模型中,建立了考虑拉压异性复合材料的非线性统一本构方程.实验验证结果表明,运用本文中所建立的本构模型能够很好地描述碳纤维/环氧(IM600/Q133)复合材料在偏轴拉伸和压缩载荷作用下的非线性响应.
关键词:
单向复合材料
,
非线性响应
,
不同屈服强度
,
本构方程
,
偏轴拉伸-压缩载荷
郝寅雷
无机材料学报
doi:10.3321/j.issn:1000-324X.2003.02.007
建立在均匀、无应力状态基础上的玻璃性质计算模型,在用于离子交换法制备的GRIN光学元件的折射率变化值(ΔN)计算时与实验结果有一定的偏差.本文对HSD(Higgins,Sun和Davis)模型和干福熹模型进行了比较,结果表明,干福熹模型用于低应力光学元件的计算时计算结果与实验值偏差较小,但对高应力GRIN光学元件的ΔN计算偏差很大;HSD模型在计算过程中分别考虑了玻璃组分的极化率因素和体积因素对其折射率的影响,在用于高应力GRIN光学元件ΔN计算时具有更强的适用性.
关键词:
梯度折射率
,
离子交换
,
玻璃
,
模型
