材料期刊网

Damping Behaviour and Mechanism of Graphite Particulate Reinforced Metal Matrix Composites

Yongchang LIU , Gencang YANG and Yili LU(State Key Lab. of Solidification Processing , Northwestern Polytechnic University , Xi'an 710072 , China)Zhengang ZHU(Lab. of Internal Friction and Defects in Solids , Institute of Solid State Physics , Chinese Academy o

材料科学技术（英文）

The effect of graphite particulate reinforcement on the resultant damping behaviour of ZA27metal matrix composites (MMCs) has been investigated in an effort to develop a new functional material. The MMCs were processed by a spray atomization and deposition technique. The damping capacity, as well as the relative dynamic modulus, was measured at frequencies of 1and 4 Hz in the 30 to 200℃ temperature range. There exists a transformation point at 55℃in the internal friction and temperature spectrum of the MMCs. It is shown from microstructural analysis that the damping capacity of ZA27 can be significantly improved by the addition of graphites particulates through spray deposition processing. Finally, the operative damping mechanism is discussed in light of the data obtained from characterization of microstructure and damping capacity.

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INTERNAL FRICTION OF GRAIN BOUNDARIES IN Fe-P AND Fe-P-La ALLOYS CONTAINING TRACE Cu

JI Jingwen WEI Quanjin GENG Dianqi WU Yuqin Northeast University of Technology , Shenyang , China Professor , Dept.of Physics , Northeast University of Technology , Shenyang 110006 , China

金属学报(英文版)

The grain boundary internal friction(GBIF)in Fe-P and Fe-P-La alloys containing trace Cu has been studied.It is found that an addition of 0.584—0.722 wt-% La obviously reduces the IF,shifts grain boundary peaks towards higher temperatures,and produces a small addi- tional peak at even higher temperature.The mechanism of GBIF is explained as the movement of defects of atomic size,namely point defects,at gram boundaries and/or their clusters un- der stress.

关键词: internal friction , null , null , null , null

NONLINEAR INTERNAL-FRICTION AND RESONANCE IN MANGANESE-COPPER ALLOYS

Journal of Materials Science

Internal friction and modulus at different amplitudes and frequencies were measured for as-cast Mn60Cu40 alloy. Strong non-linear internal friction and resonance were observed. It was proposed that the sources of these were derived from different factors. A parameter, P, which can be used to weigh up non-linear resonance of materials, is proposed. A high damping mechanism is discussed for manganese-copper alloy.

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Controversy about the Origin of the Grain Boundary Internal Friction Peak and Its Clarification

T.S.Ke (Tingsui GE)(Lab. of Internal Friction and Defects in Solids , Institute of Solid State Physics , Chinese Academy of Sciences , Hefei 230031 , China)

材料科学技术（英文）

In the seventies some scientific workers from France and ltaly suggested that the grain boundary internal friction peak (named the Ke peak in the literature) widely accepted as a grain bound ary process, is originated from the motion of lattice dislocations. Since this problem is one of fundamental importance, this controversy has drawn much international attention. Started from 1982, the Hefei research group made a critical analysis of the large amount of literature concerning this problem and performed a series of crucial experiments to clarify the controversy It is concluded that the irrelevant evidence suggested by the controverters comes from the farfetched interpretation and the mis-identification of the internal friction peaks appeared under various experimental conditions and different states of the specimens.

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The investigation of internal friction and elastic modulus in surface nanostructured materials

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

In this paper, 304 stainless steel and pure Fe specimens, which were processed by high-energy shot peening (HESP) and ultrasonic shot peening (USP) respectively, were studied by the internal friction method. Measurements were carried out on a vibrating reed apparatus. The change of internal friction and elastic modulus shows that the treatment duration of specimen is not accompanied by the corresponding persistent increase of internal friction and elastic modulus. There is a transition layer from the top surface to the inside of the materials. Young's modulus of surface shows obviously a fluctuation along the depth profile. The phenomena have never been shown by other measurement methods. The microstructure change should be related to some basic mechanism of surface layer formation. It may also explain why the improvement of mechanical properties in surface nanocrystallized materials does not simply correspond to the duration time of severe deformation. (C) 2003 Elsevier B.V. All rights reserved.

关键词: internal friction;Young's modulus;surface nanostuctured material;iron;nanocrystallization;304-stainless-steel;behavior

Internal friction and elastic study on surface nanocrystallized 304 stainless steel induced by high-energy shot peening

材料科学技术（英文）

The 304 stainless steel with nanostructured surface layer was successfully obtained by using the high-energy shot peening (HESP) method. The internal friction and Young's modulus of this kind of surface nanocrystallized material were dynamically measured by means of the vibrating reed apparatus. The results implied that different treatment time could induce different microstructure and distribution characteristic of defects in this kind of materials. It is also demonstrated that there is a transition layer between the nano-layer on surface and the coarse grain region inside. The transition layer obviously has certain influence on the overall mechanical properties.

关键词: surface nanocrystallization;internal friction;high-energy shot peening;iron;behavior

INTERNAL FRICTION AND ELASTIC CONSTANTS OF Pd-B-H ALLOYS

Y.L. Chen(Department of Materials Science and Engineering , Zhejiang University , Hangzhou 310027 , China)

金属学报(英文版)

Internal friction measurements on binary and ternary α-phase alloys of Pd with hydrogen and boron have been performed with a torsion pendulum and by observing the cttenuation of ultrasonic pulses. A pronounced damping maximum of binary Pd-B alloys at 220K and measuring frequencies of about 4Hz could not be established at a frequency of 15MH. Ternary Pd-B-H alloys show an additional damping maximum besides the hydrogen Zener effect, which is interpreted in terms of a changed jump frequency of hydrogen in the neighborhood of boron atoms.

关键词: Pd-B-H alioy , null , null , null

Investigation on microstructure and internal friction for low density TiB₂/ZL114 composites

Wenmao HUANG , Haihong ZHAN , Lingyan XU , Zhengbing XU , Jianmin ZENG

金属学报(英文版) doi:10.1016/S1006-7191(08)60091-5

TiB₂/ZL114 composites with the density of 2.733 g/cm³ were fabricated through reaction of K₂TiF₄ and KBF₄ (LSM method). The composites were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The internal friction measurements were performed on DTM-II-J dynamic modulus damping analyzer and the mechanisms were investigated. Experimental results indicate that reinforced particles are well-distributed in the matrix and the internal friction value of TiB₂/ZL114 composites is up to a maximum of 9.04x10^-3, almost twice that of ZL114. The internal friction results form dislocation vibration within the material, the sliding of grain boundary and phase interface, and together with the micro-plastic deformation caused by difference in coefficients of thermal expansion and elasticity modulus of various phases. The average internal friction values of samples with the sizes of 40 mmx4 mmx2 mm, 40 mmx8 mmx2 mm and 40~mm$\times 25 mmx2 mm are 8.83x10^-3, 8.89x10^-3, and 8.93x10^-3, respectively. Thus, the developed composites are of low density, high internal friction, and the sizes of samples have no relation to the internal friction behavior.

关键词: LSM method , null , null

EFFECT OF SLIP ORIENTATION ON STRESS RESPONSE,INTERNAL FRICTION AND ULTRASONIC ATTENUATION DURING CYCLIC DEFORMATION IN Al SINGLE CRYSTALS

XIA Yuebo ZHANG Tianyi State Key Laboratory for Fatigue and Fracture of Materials , Institute of Metal Research , Academia Sinica , Shenyang , ChinaFEI Guangtao ZHOU Xing Laboratory of Internal Friction and Defects in Solids , Institute of Solid State Physics , Academia Sinica , Hefei , China Associate Professor , Institute of Metal Research , Academia Sinica , Shenyang 110015 , China

金属学报(英文版)

The variation of cyclic stress,internal friction and ultrasonic attenuation during cyclic deformation and relations among them have been investigated with different slip orientation Al single crystals.The results indicate that the value of cyclic stress σ,internal friction Q~(-1)and ultrasonic attenuation △α depend obviously on the slip orientation.There are large differences in above three parameters for different slip orientation Al crystals.In early stage of fatigue life,σ and △α increase and Q~(-1)decreases with cycles N,and △α reached maxi- mum before σ,while Q~(-1)and σ get the valley and the peak,respectively,at same cycles.

关键词: crystal orientation , null , null , null , null , null

High-temperature internal friction, stiffness and strength of Zr-Al(Si)-C ceramics

Scripta Materialia

The temperature dependence of internal friction, stiffness and strength of Zr-Al(Si)-C ceramics was studied. For glass-free Zr-Al(Si)-C ceramics, the internal friction curve followed an exponential-like background. For liquid-phase-sintered Zr(3)Al(3)C(5), an internal peak present at 1590 K revealed the grain-boundary sliding due to wetting of glass phase at grain boundaries and triple junctions. Zr-Al(Si)-C ceramics exhibited high degrees of stiffness and strength at high temperatures up to 1600 and 1400 degrees C, respectively, which render them good high-temperature structural materials. (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: Carbide;TEM;Grain boundaries;Elastic behavior;Internal friction;liquid reaction synthesis;si-c ceramics;grain-boundary;polycrystalline ti2alc;elastic properties;oxidation;microstructure;relaxation;viscosity;zr2al3c4