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Asymmetry Behaviour between Tension and Compression for Prestrained materials under cyclic Loading

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Journal of materials Science & Technology 1993年第4期9卷 273-278页

作者： Huifen CHAI Zheng RUAN Quncheng FAN Dept.of materials Science and Engineering,Xi’an Jiaotong University,Xi’an,710049,China

The prestrained metals show substantial asymmetry between tension and compression in addition to the softening under cyclic loading, thus the cyclic creep takes place at a load-control test. The soft- ening reflects the decrease in density of dislocation and total internal stress, and the creep implies the asymmetry in back stress between tension and compression, The mechanical behaviour of the soft- ening is similar for materials with different slip modes, but their features of creep differ significantly. The creep of planar slip Cu-Zn alloy exhibits“explosively”, while that of wavy slip Cu and low car- bon steel occurs continuously and slowly. The explanation of creep behaviour via the internal dislo- cation structure was presented in this paper. According to asymmetw behaviour, it can be concluded that the internal processes of softehing also strongly depend on the slip mode. In addition, under high stress amplitude the opposite asymmetries take place for Cu and Cu-Zn alloy, it indicates that asymmetric back stresses developed in pretension have been eliminated even though the density and the configuration of dislocations have not reached equilibrium.

关键词： internal stress cyclic loading dislocation

EFFECTS OF SLIP MODE ON cyclic BEHAVIOR OF PRESTRAINED materials

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Acta Metallurgica Sinica(English Letters) 1993年第5期6卷 326-331页

作者： CHAI Huifen RUAN Zheng FAN Quncheng (Xi’an Jiaotong University,Xi’an,China CHAI Huifen,associate professor,Department of materials,Xi’an Jiaotong University,Xi’an 710049,China

The cyclic behaviours of two prestrained materials with different slip modes have been com- *** the analysis of hysterisis loops,it is suggested that the decrease in back stress dominates the cyclic process of Cu-Zn alloy with planar slip mode,while the decrease in frictional stress is the main factor affecting the behaviour of Cu with wavy slip *** re- lation between the dislocation configuration and internal stress has been also *** means of the relation just mentioned,the variations of dislocation configuration before and after fatigue of the two materials,the differences in their softening mechanism and mechani- cal behaviour could be interpreted.

关键词： slip mode fatigue softening hysteresis loop internal stress

Martensite Aging Effect and Thermal cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys

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Journal of materials Science & Technology 2001年第3期17卷 359-362页

作者： Wei Cai School of materials Science and Engineering, Harbin Institute of Technology, Harbin 15000k, China Kazuhiro Otsuka Institute of materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan E-mail: weicai@*** Sch. of Mat. Sci. and Eng. Harbin Inst. of Technol. Harbin 150001 China

The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M, and Af temperatures in Ti50Pd50-xNix (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.

关键词： Ti Martensite Aging Effect and Thermal cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys Pd Ni

Preparation and Microstructure of a Si-Mo Fused Slurry Coating on Carbon/Carbon Composites for Oxidation Protection

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Journal of materials Science & Technology 2001年第1期17卷 57-58页

作者： Haitao FANG Jingchuan ZHU and Zhongda YIN School of materials Science and Engineering, Harbin institute of Technology, Harbin 150001, China Jae-Ho Jeon and Yoo-Dong Hahn materials Engineering Department, Korea institute of Machinery & materials, Changwon Sch. of Mater. Sci. Harbin Inst. of Technol. Harbin 150001 China

A coating of composition Si-40Mo (wt pct) was prepared by fused slurry coating method on the two-dimensional carbon/carbon (2D-C/C) composite to improve oxidation resistance. In the procedure of the fabrication, pure St slurry inner layer in the pre-coating was necessary to apply because of infiltration of liquid Si into the substrate during the sintering. The coating consists of Si continuous phase and MoSi2 particles. In addition, the infiltration of Si into the substrate and the SiC reaction layer between the coating and the C/C composite were observed. Oxidation behavior of coated and uncoated C/C composites was studied in cyclic mode. The oxidation resistance and the thermal shock resistance of the Si-Mo fused slurry coating were quite excellent at 1370℃.

关键词： Si Preparation and Microstructure of a Si-Mo Fused Slurry Coating on Carbon/Carbon Composites for Oxidation Protection Mo

DEFORMATION　AND　FRACTURE　OF　TiAl　PST　CRYSTALS　UNDER　MONOTONIC　AND　cyclic　LOADING

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Acta Metallurgica Sinica(English Letters) 1995年第Z1期8卷 329-338页

作者： Y.Umakoshi T. Nakano and H .Y. Yasuda (Department of materials Science and Engineering, Faculty of Engineering, Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565 Japan) Osaka Univ Osaka Japan

Plastic behaviour of TiAl polysynthetically twinned (PST) crystals is reviewed to show our knowledge and understanding for receiving a good combination of strength and ductility of two phase TiAl alloys under monotonic and cyclic loading conditions. Anisotropy and mechanism of strength, ductility, toughness. cyclic hardening and fatigue life are described focusing on the effect of lamellar structure.

关键词： Fatigue. Deformation TiAl Intermetallic Compound

Influence of nanometric CeO2 coating on high temperature oxidation of Cr

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Progress in Natural Science:materials International 2007年第5期17卷 601-606页

作者： Jin Huiming , Zhang Linnan and Liu Xiaojun (materials Research Center, Department of Mechanical Engineering, Yangzhou University, Yangzhou 225009, China College of materials Science and Engineering, North-East University, Shenyang 110014, China) materials Research Center Department of Mechanical Engineering Yangzhou University Yangzhou 225009 China College of materials Science and Engineering North-East University Shenyang 110014 China

Isothermal and cyclic oxidation behavior of chromium and its superficially applied nanometric CeO2 samples were studied at 900℃in air. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and high resolution electronic microscopy (HREM) were used to examine the morphology and micro-structure of oxide films. It was found that ceria addition greatly improved the anti-oxidation ability of Cr both in isothermal and cyclic oxidizing experiments. Acoustic emission (AE) technique was used in situ to monitor the cracking and spalling of oxide films, and AE signals were analyzed in time-domain and number-domain according to the related oxide fracture model. Laser Raman spectrometer was also used to study the stress status of oxide films formed on Cr with and without ceria. The main reason for the improvement in anti-oxidation of chromium was that ceria greatly reduced the growing speed and grain size of Cr2O3. This fine-grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of compressive stress by means of creeping, and maintained the ridge character and relatively low internal stress level. Meanwhile, ceria application reduced the size and the number of interfacial defects, while remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.

关键词： oxidation stress CeO2 nanoparticle coating chromium.

Tetragonal Domain Switching via Reversible tm Phase Transformation

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Journal of materials Science & Technology 1996年第4期12卷 255-260页

作者： Haiyan ZHU and Zhicheng XU(Dept. of materials Science and Engineering, Zhejiang University, Hangzhou 310027, China) Dept. of materials Science and Engineering Zhejiang University Hangzhou 310027 China

Grinding-induced tm phase transformation and the resultant texture in ceria-yttria-doped tetragonal zirconia polycrystals with varied tetragonality have been studied by XRD. It is observed that the reversible tm phase transformation occurs during grinding and the intensity ratio of I(002)t/I(200)t increases with the transformability. The author proposes that the texture induced by grinding at low temperatures is due to the tetragonal variant reorientation via cyclic,reversible tm phase transformation, termed 'transformational domain switching', instead of the ferroelastic one

关键词： Jun Am Chen Tetragonal Domain Switching via Reversible t m Phase Transformation

The strain amplitude-controlled cyclic fatigue behavior of Al2O3 fiber reinforced Al-Si alloy composite at elevated temperatures

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Progress in Natural Science:materials International 2012年第2期22卷 153-159页

作者： Guohua Zhang a,c,Bingchao Li b,Jianxin Zhang b,Wei Cai a a School of materials Science and Engineering,Harbin Institute of Technology,Harbin 150001,China b School of materials Science and Engineering,Shandong University,Jinan 250061,China c Shandong Binzhou Bohai Piston Co.,Ltd,Binzhou 256602,China School of materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Shandong Binzhou Bohai Piston Co. Ltd Binzhou 256602 China School of materials Science and Engineering Shandong University Jinan 250061 China

The strain amplitude-controlled fatigue characteristics of an Al-Si casting alloy and its composite reinforced with 17 vol%Al2O3 fibers(Al-Si/Al2O3)are studied at three different *** the alloy and the composite showed different degrees of cyclic softening at elevated *** the temperature,fatigue damage of either the alloy or the composite occurred with varying mode from brittle fracture of silicon particles to their separation from the aluminum *** is explained by the different thermal expansion coefficients of silicon particles and the aluminum *** reinforcement Al2O3 fibers in the composite showed a similar damage behavior with those silicon particles despite temperature variation.

关键词： Metal matrix composites Squeeze casting Fatigue Fracture Temperature

cyclic DEFORMATION OF COARSE GRAINED POLYCRYSTALLINE PURE Al——Ⅱ.FRACTURE SURFACE MORPHOLOGY

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Acta Metallurgica Sinica(English Letters) 1992年第5期5卷 330-335页

作者： XIA Yuebo WANG Zhongguang State Key Laboratory for Fatigue and Failure of materials,Institute of Metal Research,Academia Sinica,Shenyang,China

SEM photos for very coarse grained and high ductile polycrystalline pure Al show following characteristics:A few fracture sources are concentrated,the crack propagates in fan-shape near them,and the fatigue striations are cyclic cleavage *** striation consists of a wide cleavage facet and a narrow cleavage *** stages often blunt due to plastic *** fatigue striations are clear and continual,and distribute over whole zone of stage Ⅱ crack *** kinds of fatigue striations form in different levels,are conjoined by a“twisted baked piece of pastry”*** secondary crack along the fatigue striations was observed *** of them have already developed into secondary macrocracks and secondary fatigue striations were found clearly on secondary fracture sur- *** fracture surface can be divided into two parts,initiation and propagation zone of the crack,however,no statical-fracture zone was *** mechanism to form striations was preliminarily discussed.

关键词： fatigue crack Al fatigue striation secondary crack cleavage tongue