H.P. Chen and Z.J. Deng (State Key Lab. for Mechanical Behavior of Materials
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Xi'an Jiaotong University
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Xi'an 710049
,
China)
金属学报(英文版)
The effect of specimen thinkness on JR resistance curve has been investigated using low and middle strength steels. As the J dominance regime is reached, the initial J-integral values, J(i), are definite even if the elastic component Ji(e) and plastic component Ji(p)vary with the thinkness of specimen. The wider the specimen width, the larger the Ji(e)/Ji and the smaller the Ji(p)/Ji. The crack propagation resistance, dJR/da and dJp/da, decreases, while dJe/da increases linearly with increasing specimen thinness.Based on the above experimental results, an empirical formula dJ/da = α+β. B is given, which can be used to evaluate the safety of practical structural components.A modified J-integral is presented, upon which a new view is Put forward that the increase in crack growth resistance is induced mainly by the increase in the plastic J-integral component with the crack propagation,
关键词:
: fracture mechanics
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null
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null
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null
张淑佳
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卢炎麟
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任立义
,
洪起超
金属学报
对20 g钢高温断裂韧性随加载速率的变化规律进行了实验研究.在400℃和500℃下,分别测量了几种加载速率下20 g钢的Ji值.实验结果表明:Ji值随应变速率的增大而有较大幅度的降低;在同一应变速率下,400℃时的Ji值小于500℃时的Ji值;400℃时裂纹扩展比500℃时更快.因此,当温度在400℃附近时更应注意避免超载.
关键词:
断裂韧性
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null
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null
周兰花
,
陶东平
,
曾富洪
稀有金属
doi:10.3969/j.issn.0258-7076.2011.04.011
在求解分子相互作用体积模型(MIVM)中的分子对位能参数B(ij),B(ji)时,为避免出现计算超量问题,基于遗传算法,提出了一种新算法--多个体参与交叉遗传算法,并给出了新算法的实现方案.在新算法中,采用了轮盘选种法与优秀个体保存、多个体参与交叉和多点变异等策略;选择B(ij),B(ji)个体时,按照适应度函数值愈大,个体被选中的概率愈大的原则,选择二元合金溶液中一组元活度的计算值与实验测定值之间偏差(σ)建立的适应度函数f(x)最大为优化目标.采用Matlab软件编制新算法下的B(ij),B(ji)计算程序,并分别求算了Cd-Bi,Cd-Pb,Cd-Sn,Bi-Pb,Bi-Sn,Pb-Sn等6组二元合金溶液在773 K下合金溶液的参数B(ij),B(ji)优化值.由B(ij),B(ji)计算优化值和其他一些资料数据,使用MIVM进一步预测773 K下Cd-Bi-Pb,Cd-Bi-Sn,Cd-Pb-Sn,Cd-Bi-Pb-Sn多元合金溶液中组元Cd的活度,模型预测值与实验测定值之间的相对误差低于4.6%,偏差低于0.022,两者吻合很好.结果表明,所提出的多个体参与交叉遗传算法为求解MIVM中的参数B(ij),B(ji)提供了一种有力工具,从而也能提高MIVM对多元合金溶液中组元活度的预测效果.
关键词:
MIVM模型
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分子对位能参数Bij
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Bji
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遗传算法
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活度
Haihua LIU
金属学报(英文版)
doi:10.1016/S1006-7191(08)60120-9
A novel method was reported to measure the remnant magnetic field in Lorentz mode in a FEI Tecnai F20 transmission electron microscope equipped with a Lorentz lens. The movement of the circle Bloch line of the cross-tie wall in Permalloy is used to measure the remnant magnetic field by tilting the specimen and adjusting the objective lens current. The remnant magnetic field is estimated to be about 17 Oe, in a direction opposite to that of the objective lens magnetic field. The remnant magnetic field can be compensated by adjusting the value of the objective lens current.
关键词:
Lorentz electron microscopy
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Lorentz lens
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remnant magnetic field
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Permalloy
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cross-tie walls
Jun Gong
材料科学技术（英文）
Aluminum doped zinc oxide (AZO) thin films were prepared by DC magnetron sputtering at low substrate temperature. A coaxial solenoid coil was placed near the magnetron target to enhance the plasma density (Ji). The enhanced plasma density improved significantly the bulk resistivity (ρ) and its homogeneity in spatial distribution of AZO films. X-ray diffraction (XRD) analysis revealed that the increased Ji had influenced the crystallinity, stress relaxation and other material properties. The AZO films deposited in low plasma density (LPD) mode showed marked variation in ρ (ranging from ~6.5×10-2 to 1.9×10-3 Ω·cm), whereas those deposited in high plasma density (HPD) mode showed a better homogeneity of films resistivity (ranging from ~1.3×10-3 to 3.3×10-3 Ω·cm) at different substrate positions. The average visible transmittance in the wavelength range of 500−800 nm was over 80%, irrespective of the deposition conditions. The atomic force microscopy (AFM) surface morphology showed that AZO films deposited in HPD mode were smoother than that in LPD mode. The high plasma density produced by the coaxial solenoid coil improved the electrical property, surface morphology and the homogeneity in spatial distribution of AZO films deposited at low substrate temperature.
关键词:
Sputtering
刘天成
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卢志超
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李德仁
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孙克
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周少雄
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卢燕平
功能材料
采用电沉积方法从硫酸盐体系镀液中沉积得到Fe18Ni82合金薄膜.运用扫描电子显微镜(SEM),原子力显微镜(AFM),透射电子显微镜(TEM)和X射线衍射分析(XRD)以及磁测量设备分别对薄膜的表面形貌、显微结构和磁性能进行表征和测量.同时利用万能材料试验机和显微硬度计测量了薄膜的力学性能.结果表明:电沉积制备的Fe18Ni82合金薄膜成分均匀,表面平整、光亮、致密,晶粒大小为40～50 nm.薄膜是以Ni为溶剂原子,Fe为溶质原子的置换型固溶体,只存在单一的fcc相,Fei8Ni82合金薄膜沿(111)面有较强的择优取向.镀态Fei8Ni82合金薄膜在50 Hz交流磁场下,测得其饱和磁感应强度为1.08 T,最低矫顽力为20 A/m.19 μm厚的纳米晶薄膜的断裂应力达到785MPa,显微硬度达到605Hv.
关键词:
铁镍合金
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薄膜
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电沉积
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纳米结构
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性能
