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SUPERPLASTICITY AND DIFFUSION bONDING OF IN718 SUPERALLOY

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Acta Metallurgica Sinica(English Letters) 2007年第4期20卷 307-312页

作者： W.b. Han K.F. zhang b. Wang D.z. Wu School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The superplasticity and diffusion bonding of IN718 superalloy were studied in this article. The strain rate sensitivity index m was obtained at different temperatures and various initial strain rates using the tensile speed mutation method; m reached its maximum value 0.53 at an initial strain rate of 1×10^-4s^-1 at 1253K. The diffusion bonding parameters, including the bonding temperature T, pressure p, and time t, affected the mechanism of joints. When the bonded specimen with 25μm thick nickel foil interlayer was tensile at room temperature, the shear fracture of the joints with nickel foil interlayer took place at the IN718 part. Microstructure study was carried out with the bonded samples. The microstructure shows an excellent bonding at the interfaces. The optimum parameters for the diffusion bonding are： T = 1273-1323K, p = 20-30MPa, t = 45-60min.

关键词： superplasticity diffusion bonding nickel foil IN718 alloy

FATIGUE PROPERTIES OF AUSTEMPERED DUCTILE IRON(ADI)IN WATER ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 122-130页

作者： Q.z.Cai b.K.Wei Y.Tanaka StateKeyLabofPlasticFormingSimulation＆Dies／MouldTechnology FacultyofMaterialsScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China DepartmentofMechanicalSystemsEngineering MuroranInstituteofTechnologyMuroran050-8585Japan

The acicular ferrite in austempered ductile iron (ADI) matrix around graphite wascorroded preferentially in wet condition, promoting crack origination and propagationand resulting in the disappearance of ADI fatigue limit. ADI fatigue strength wasgradually reduced with increasing the time of test and was reduced by 50% in wetcondition at 10~7 cycles compared with the fatigue limit in dry condition. The fatiguestrength variation of ferritic ductile iron in wet condition was similar to that of ADI.The ferritic ductile iron, however, has better corrosion resistance so that the fatiguestrength was lowered only by 10% in wet condition at 10~7 cycles compared with thefatigue limit in dry condition. On the other hand, the fatigue limits of ADI and ferriticductile iron were dropped by 32% and 25% in tap water dipping 480h/dry conditionrespectively compared with those in dry condition. The reduction of fatigue limit wasattributed to corrosion pits formation correlated with stress concentration, resultingin origination and propagation of fatigue crack.

关键词： anstempered ductile iron water environment corrosion fatigue crack fatigue strength

Active vibration control of functionally graded beams with piezoelectric layers based on higher order shear deformation theory

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Earthquake Engineering and Engineering Vibration 2016年第4期15卷 611-620页

作者： K. bendine F.b. boukhoulda M.Nouarit z. Satla Mechanics of Structures and Solids Laboratory Department of Mechanics Faculty of technology Djillali Liabes University of Sidi Bel-Abbes Algeria University of Lorraine Laboratoire d'Energetique et de Mecanique Theorique et Appliquee LEMTA CNRS-UMR 7563 Mines Nancy Nancy 88100 France

This paper reports on a study of active vibration control of functionally graded beams with upper and lower surface-bonded piezoelectric layers. The model is based on higher-order shear deformation theory and implemented using the finite element method （FEM）. The proprieties of the functionally graded beam （FGb） are graded along the thickness direction. The piezoelectric actuator provides a damping effect on the FGb by means of a velocity feedback control algorithm. A Matlab program has been developed for the FGb model and compared with ANSYS APDL. Using Newmark＇s method numerical solutions are obtained for the dynamic equations of FGb with piezoelectric layers. Numerical results show the effects of the constituent volume fraction and the influence the feedback control gain on the frequency and dynamic response of FGbs.

关键词： beams piezoelectric finite element method functionally graded materials vibration control

Constitutive equation and model validation for a 31 vol.% b_4Cp/6061Al composite during hot compression

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Journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： L. zhou C. Cui Q.z. Wang C. Li b.L. Xiao z.Y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of b4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% b4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in b4C/AI composites.

关键词： Composites b4C/AI Constitutive equation Hot compression Finite element simulation

Structure and Thermal Parameters of Ni_(20)Pd_(80) Alloy

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Journal of Materials Science & Technology 2009年第2期25卷 208-210页

作者： S. Ahmad A.b. ziya A. Aziz z.I. zafar Department of Physics Bahauddin Zakariya University Department of Chemistry Bahauddin Zakariya University

The structure and thermal parameters of Ni20Pd80 alloy were studied by X-ray diffraction（XRD）. The diffraction experiments performed in the temperature range of 308-1100 K revealed that the alloy formed a face centered cubic （fcc） Al-type structure. The temperature dependence of the lattice parameters was investigated by using the bragg line displacement method showing that the lattice parameter increases with the increase of temperature. The mean linear thermal expansion （MLTE（%））, coefficient of thermal expansion （CTE, α）, the characteristic Debye temperature （（θD） and mean square amplitudes of vibration were determined from XRD data. The value of Debye temperature was found to be 253 K. It was found that temperature factor was independent of the static displacements.

关键词： Alloys Structure Thermal parameters X-ray diffraction (XRD)

THEORETICAL ANALYSIS FOR THE MOTION AND TEMPERATURE OF MELT DROPLETS IN SPRAY DEGASSING PROCESS

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Acta Metallurgica Sinica(English Letters) 2007年第3期20卷 193-198页

作者： R.z. Wu z.K. Qu b.D. Sun D. Shu J. Wang College of Materials Science ＆ Chemical Engineering Harbin Engineering University Harbin 150001 China State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University Shanghai 200030 China Department of Chemistry Harbin Normal University Harbin 150025 China

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process couM be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets wouM solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results,

关键词： spray degassing hydrogen removal aluminum melt motion temperature

Improving the strength and SCC resistance of an Al-5Mg-3zn alloy with low-angle grain boundary structure

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Journal of Materials Science & Technology 2023年第30期161卷 63-73页

作者： z.C.Tang W.Xu D.Y.zhao b.zhang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

The strength of traditional Al-Mg alloys is relatively low because it mainly relies on solid solution *** a third component to form precipitation can improve their strength,but it usually leads to high-stress corrosion cracking(SCC)sensitivity due to the formation of high-density precipitates at grain boundaries(Gbs).So far,it is still challenging to improve the strength of Al-Mg alloys without re-ducing SCC ***,a nanostructured Al-5Mg-3 zn alloy with a good yield strength of 336 MPa and good elongation was successfully *** dynamic plastic deformation and appropriate anneal-ing treatment,near-equiaxed nanograins were introduced in the nanostructured Al-5Mg-3 zn alloy with a high proportion(71%)of the low-angle grain *** statistical investigations show that the pre-cipitation of active T’phase at Gbs has been greatly suppressed in the nanostructured Al-5Mg-3 zn alloy at sensitized conditions,and the area fraction of Gb precipitates is reduced from 72%to 21%,which sig-nificantly decreases the SCC *** study provides guidance for developing advanced Al-Mg alloy with high SCC resistance.

关键词： Al-5Mg-3 zn alloy Stress corrosion cracking Low angle grain boundary Nanostructured Dynamic plastic deformation

Dielectric and infrared properties of SrTiO_3 single crystal doped by 3d (V,Mn,Fe,Ni) and 4f (Nd,Sm,Er) ions

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Chinese Physics b 2014年第2期23卷 369-374页

作者： S.Maletic D.Maletic I.Petronijevic J.Dojcilovic D.M.popovic Faculty of Physics University of Belgrade Institute of Physics University of Belgrade

In this study, the effects of doping by 3d （V, Mn, Fe, Ni） and 4f （Nd, Sm, Er） ions on dielectric and infrared properties of SrTiO3 （STO） single crystals are investigated. It is well known that doping of the SrTiO3 can change the dielectric properties of the STO from an insulator to an n-type semiconductor, and even to a metallic conductor. Dielectric and infrared （IR） properties of the undoped STO and doped STO single crystals are analyzed using dielectric spectroscopy （80 kHz-5 MHz）, transmission （200 cm^-1-4000 cm^-1）, and reflection spectroscopy （50 cm^-1-2000 cm^-1）. It is found that doping by the 3d ions reduces the value of dielectric permittivity, but the trend of temperature dependence of the dielectric permittivity remains almost unchanged. On the other hand, dielectric spectroscopy measurements for samples doped by 4f ions show the anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition. There are two fractures of temperature dependences of inverse dielectric permittivity εr^-1 （T）. Transmittance spectroscopy measurements show that there are differences in the shape of the spectrum in the mid-IR region between the undoped STO and the one doped by 4f ions. The differences in the reflectance spectrum between the STO：Nd and STO are analyzed in detail.

关键词： doping dielectric properties phase transitions infrared spectroscopy

Evaluating instrumented Charpy impact strain signals using curve fitting equations

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Journal of Central South University 2014年第2期21卷 600-609页

作者： M.b.Ali S.Abdullah M.z.Nuawi A.K.Ariffin z.M.Nopiah Department of Mechanical and Materials Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia Department of Structure and Material Faculty of Mechanical EngineeringUniversiti Teknikal Malaysia Melaka

An effective and simple way to develop equations from impact strain signals was *** research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact *** this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition *** 6061-T6 was used to extract strain responses on the striker during Charpy impact *** analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact *** I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and *** and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz *** equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.

关键词： charpy impact curve fitting I-kaz signal and strain