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Aging Effect on Elapsed Time of Serrations in Al-Li Single Crystals

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Journal of materials Science & Technology 1998年第4期14卷 353-356页

作者： Tian, BH Yan, MG Chen, CQ beijing inst aeronaut mat Beijing 100095 Peoples R China beijing Univ aeronaut & Astronaut Beijing 100083 Peoples R China

Elapsed time of serrations in AI-Li single crystals was investigated with two definitions: one is the time elapsed in one cycle of serrations, the other is the average elapsed time within a strain limit. Elapsed time of individual serration appears independent on stress drops during serrated flow. It primarily distributes within the limits of short elapsed time in peak aged condition compared with underaged and overaged conditions, corresponding to low level of the average elapsed time that appears indifferent to increasing strain. It seems that shearing behaviour of delta' particles could be responsible for the variations in elapsed time of serrations.

关键词： Aluminum alloys

Characteristics of Serrated Flow in Al-Li Single Crystals

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Journal of materials Science & Technology 1998年第5期14卷 465-469页

作者： Tian, Baohui Yan, Minggao Zhang, Yonggang Chen, Changqi inst aeronaut mat Beijing 100095 Peoples R China beijing Univ aeronaut & Astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

Serrated flow has been investigated in binary Al-Li single crystals treated from as-quenched to overaged conditions. Serration was observed during the deformation of crystals aged from 10 to 100 h at 448 K, but not in the as-quenched and naturally aged conditions. The number of stress drops for serration persistently increases within small stress drop limits as aging time increases until attainment of peak-aged condition. Crystal orientations have some effects on stress drops for serration. (Edited author abstract) 16 Refs.

关键词： Aluminum alloys

A Near-bulk Quasicrystal Alloy Formed in Zn-Mg-Y System

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Journal of materials Science & Technology 1997年第2期13卷 141-144页

作者： Tang, YL Shen, NF Liu, XF Luo, ZP Liu, BC inst aeronaut mat BEIJING 100095PEOPLES R CHINA TSING HUA UNIV BEIJING 100084PEOPLES R CHINA

Zn-Mg-Y and Mg-Zn-Y-Zr ingots with different chemical compositions were; investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The icosahedral phases were found in all alloys studied in present work under the as-cast conditions. There are nearly all quasicrystal phases with some MgZn2 Laves phase in a Zn-28.31Mg-13.80Y alloy (wt pet). After annealing at 400 degrees C for 8 h, the quasicrystal phases transformed to an fee ''W'' phase in an Mg-5.57Zn-1.08Y-0.60Zr alloy (wt pet).

关键词： Zinc alloys

Study of Solidification Shrinkage of Ductile Iron in Dry Sand Molds

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Journal of materials Science & Technology 1999年第3期15卷 245-250页

作者： Li, JR Liu, BC beijing inst aeronaut mat Beijing 100095 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The effects of metallurgical and processing parameters on the formation of solidification shrinkage in ductile iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in ductile iron castings were discussed. A regression equation relating these variables to the formation of shrinkage was derived based upon the orthogonal experiments conducted.

关键词： Nodular iron

Microstructure and Tensile Properties of Spray-deposited IC6 Alloy

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Journal of materials Science & Technology 1998年第2期14卷 143-146页

作者： Mi, Guofa Li, Zhou Tian, Shifan Zhao, Xianguo Luo, Zhiping Zeng, Songyan Li, Qingchun inst aeronaut mat Beijing 100095 Peoples R China Harbin inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China

The microstructure and mechanical properties of a Ni//3 Al based Ni-Al-Mo superalloy-IC6 which possesses low impurity content and high density by spray deposition technique have been studied. The results indicate that the IC6 alloy has good tensile strength and elongation both at room and intermediate temperatures. (Edited author abstract) 6 Refs.

关键词： Nickel alloys

Ballistic Penetration of Dyneema Fiber Laminate

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Journal of materials Science & Technology 1998年第3期14卷 265-268页

作者： Zhang, Zuoguang Shen, Shiguang Song, Huancheng Zhang, Daxing beijing Univ aeronaut & Astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

UHMWPE fiber (Dyneema) reinforced composites are an important class of materials for armors. These materials provide superior ballistic performance to the armor, such as the military armor systems requiring a reduction in back-armor effects or a substrate for hardened facings of steel or ceramic. The reported work characterized the ballistic impact and mechanical performance of Dyneema fiber in composite laminates. The capability of the laminate to absorb ballistic impact energy was influenced by the impact velocity and the laminate areal density. Two kinds of penetration were compared and a two-step model for the penetration was proposed. (Edited author abstract) 3 Refs.

关键词： Fiber reinforced materials

Annealing Effect on Mechanical Properties of Ti_(51)Ni_(13)Pd_(36)High Temperature Memory Alloy

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Journal of materials Science & Technology 2000年第5期16卷 531-533页

作者： Xu, HB Hu, SQ Jiang, CB Gong, SK beijing Univ aeronaut & Astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

The high temperature shape memory alloy Ti51Ni13Pd36 was subjected to a cold working and annealing treatment to improve its mechanical properties and the shape memory effect. It was found that recovery of the cold worked alloys started at near 673 K and the recrystallization temperature was at about 748 K. The grain size decreased with the increase of annealing temperature below 923 K and then increased when above 923 K. The smallest average grain size of about 3.5μm, which is approximately 10 times smaller than the hot rolled one, permitted the best combination of the mechanical properties in the alloy annealed at 923 K for 1h. The cold rolling raised the peak temperature of reverse transformation. This temperature dropped very sharply when the specimen was annealed at temperatures higher than 673 K.

关键词： Alloys

Toughness and Hot/Wet Properties of a Novel Modified BMI/Carbon Fiber Composite

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Journal of materials Science & Technology 2001年第1期17卷 17-18页

作者： Zhang, B.Y. Chen, X.B. Li, P. Yi, X.S. beijing inst. of aeronaut. mater. Beijing 100095 China

The toughness and hot/wet properties of a novel modified bismaleimide (BMI) 5428/carbon fiber composite were investigated. Results indicate that the prepared BMI/T700 composite has high toughness, excellent hot/wet properties and mechanical properties. The compression strength of the 5428/T700 composite after impact (CAl) is 260 MPa, and the hot/wet test results show that the long-term service temperature of 5428/T700 composite can maintain at 170°C.

关键词： BMI Toughness and Hot/Wet Properties of a Novel Modified BMI/Carbon Fiber Composite

Microstructure of Al-Si Alloys Rapidly Solidified from the Different Temperature Melts

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Journal of materials Science & Technology 1999年第3期15卷 225-228页

作者： Gui, MC Jia, J Song, GS Li, QC beijing inst aeronaut mat Natl Key Lab Adv Composites Beijing 100095 Peoples R China Harbin inst Technol Harbin 150001 Peoples R China

Hypo- and hyper-eutectic At-Si alloys were rapidly solidified from the tow or high temperature melt using water quenching and melt-spinning technique. The differences in microstructure of rapid solidification alloys were studied by scanning and transmission electron microscopy, and X-ray diffraction methods. The primary silicon in the Al-22(wt pct)Si alloy quenched in room temperature water from high temperature melt was smaller than that quenched from low temperature melt. Compared with the ribbons spun from low temperature melt, the ribbons spun from high temperature melt had finer Al-rich and Si-rich phase particles in either Al-7(wt pct)Si or Al-18(wt pct)Si alloy. The mechanism was explained by the nature of the liquid structure.

关键词： Aluminum alloys