Ying Yan
,
Wan-Peng Deng
,
Zhan-Feng Gao
,
Jing Zhu
,
Zhong-Jun Wang
,
Xiao-Wu Li
金属学报(英文版)
doi:10.1007/s40195-016-0373-6
To explore the coupled effect of temperature T and strain rate ε˙ε˙ on the deformation features of AZ31 Mg alloy, mechanical behaviors and microstructural evolutions as well as surface deformation and damage features were systematically examined under uniaxial tension at T spanning from 298 to 523 K and ε˙ε˙ from 10-4 to 10-2 s-1. The increase in T or the decrease in ε˙ε˙ leads to the marked decrease in flow stress, the appearance of a stress quasi-plateau after an initially rapid strain hardening, and even to the occurrence of successive strain softening. Correspondingly, the plastic deformation modes of AZ31 Mg alloy transform from the predominant twinning and a limited amount of dislocation slip into the enhanced non-basal slip and the dynamic recrystallization (DRX) together with the weakened twinning. Meanwhile, the cracking modes also change from along grain boundaries (GBs) and at twin boundaries (TBs) or the end of twins into nearby GBs where the DRX has occurred. The appearance of a stress quasi-plateau, the formation of large-sized cracks nearby GBs, and the occurrence of continuous strain softening, are intimately related to the enhancement of the non-basal slip and the DRX.
关键词:
AZ31
,
Mg
,
alloy
,
Uniaxial
,
tension
,
Temperature
,
Strain
,
rate
,
Deformation
,
Damage
,
Twinning
F. Huang N.R. Tao K. Lu
材料科学技术（英）
The microstructures and hardness of pure Al samples subjected to plastic deformation with different temperatures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.
关键词:
Dynamic plastic deformation
,
Microstructure
,
Hardness
,
Strain rate
,
Temperature
X.S. Zheng*
金属学报(英文版)
Mold is the heart of the continuous casting machine. Heat transfer and solidification in a water- cooled mold are the most important factors during the continuous casting of steel. For studying the temperature distribution of a mold wall, a simulated apparatus of mold was designed and experiments were performed by it. The measured results indicated that the mold wall temperature approaches the temperature of cooling-water. An equivalent thermal-conductivity coefficient was proposed and deduced on the basis of the conclusion of the experiments. This coefficient was applied to solve the heat transfer between the melt and cooling water, and to characterize the heat transfer capacity of the mold. By this equivalent thermal-conductivity coefficient, it is very easy and convenient to numerically simulate the solidification process of continuous casting. And the calculation results are in agreement with the experiments. The effects of casting speed and water flow rate on the mold temperature field were also discussed.
关键词:
continuous casting mold
,
casting
,
mold
,
Temperature
,
fie
F. Huang N.R. Tao K. Lu
材料科学技术（英）
The microstructures and hardness of pure Al samples subjected to plastic deformation with different temperatures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation (DPD). Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.
关键词:
Dynamic plastic deformation
,
Microstructure
,
Hardness
,
Strain rate
,
Temperature
Xiying ZHOU
,
Peiyao LI
,
Junming LUO
,
Shiqiang QIAN
,
Jianhua TONG
材料科学技术（英）
Dry sliding friction between the Al¬59Cu¬25.5Fe¬12.5B¬3 quasicrystals (QCs)/coating of the diamond-like carbon (DLC) was carried out by self-made tribometer under different conditions. The influences of four parameters (temperature, sliding velocity, applied load, atmosphere) on friction and wear of quasicrystal surface were studied. Microstructure of quasicrystal, morphology of worn surface, and wear debris were observed by scanning electron microscopy (SEM). The results showed that for QCs, the friction coefficient and roughness of worn surface were influenced by the parameters, especially greatly by the temperature. With rise of the applied load and sliding velocity, the friction coefficient decreased. The dominant wear mechanism at 350℃ was delamination for QCs. The cracks formed on the worn surface during the friction. Moreover, phase transformation was not observed on worn surface of QCs at 350℃. All the results are discussed and explained.
关键词:
Quasicrystal
,
null
,
null
王超
,
刘婷婷
,
蒋立异
,
廖文和
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2014.06.014
硅酸铝纤维供应商往往只提供客户硅酸铝纤维在某一温度的热导率,难以指导隔热结构的设计.本文针对市场上常用的硅酸铝纤维板,设计了隔热性能测试装置,实验获得硅酸铝纤维温度随时间的变化曲线,并进行了有限元仿真分析.研究表明,硅酸铝纤维隔热效果稳定且具有一定的抗热辐射能力.有限元分析结果与实验数据基本一致,说明采用有限元分析方法能够支持设计人员较好预测隔热效果.
关键词:
硅酸铝纤维
,
隔热性能
,
温度
,
ANSYS
,
边界条件
徐斌
,
吴锋
,
曹高萍
,
杨裕生
新型炭材料
doi:10.3969/j.issn.1007-8827.2006.01.003
将PAN预氧化纤维在400℃～900℃炭化,经CO2活化得到一系列活性炭纤维,表征了其比表面、孔容和孔径分布等微结构参数,研究了炭化温度对CO2活化PAN基活性炭纤维微结构的影响.结果表明,炭化温度对活性炭纤维的比表面和孔结构有显著影响,适中的炭化温度(600℃)有利于得到高比表面积、大的孔容和孔径.
关键词:
活性炭纤维
,
炭化
,
温度
,
微结构
魏斌
,
丘明
,
张宏杰
,
诸嘉慧
,
陈盼盼
,
杨艳芳
低温物理学报
在实际的超导电力装置运行过程中,超导带材可能由于电力系统中诸如系统短路故障等各种动态过程,承受短路大电流、不平衡电流的冲击,以及由此而产生的电磁、机械应力、热量的作用而失超,因此,研究热冲击对超导材料性能的影响对超导电力装置失超保护非常重要.本文以第二代高温超导(YBCO)带材为样品,模拟实际超导电力装置中带材的绝热环境,通过外加电源对超导带材进行热冲击,研究YBCO带材在不同情况的热冲击条件下的失超过程以及带材温度和超导性能的变化.试验结果表明:对于美国Superpower公司生产的YBCO工程带材,瞬时温度超导300K后,带材的临界电流下降,瞬时温度超过500K,带材可能出现烧断现象.
关键词:
YBCO
,
温度
,
恢复特性
,
失超
牛一凡
,
杨赢
,
姚佳伟
宇航材料工艺
doi:10.3969/j.issn.1007-2330.2016.02.014
通过拉伸实验获得碳纤维增强聚醚醚酮复合材料(CF/PEEK)拉伸性能随温度的变化关系,并利用扫描电子显微镜观察断口形貌,研究分析了材料高温损伤机理.结果表明,随着环境温度的升高,碳纤维/PEEK的弹性模量与拉伸强度显著降低,在温度达到220℃时,分别下降89.20％和71.18％;断裂伸长率持续上升,在220℃时达到8.84％.弹性模量与断裂伸长率在Tg附近变化显著,主要原因是高温下纤维/树脂界面脱粘和树脂由玻璃态转化为高弹态后拉伸性能的显著变化.借助有限元方法计算由该材料制成的驾驶舱方向舵踏板在不同温度下的疲劳寿命,得出疲劳寿命随温度的升高而下降.在Coffin-Manson方程和通用斜率方程的基础上总结得出该材料疲劳寿命与温度的关系.
关键词:
聚醚醚酮
,
复合材料
,
温度
,
拉伸性能
,
疲劳寿命
