航空材料学报

Precipitation Hardening Behavior of Al-4Cu-1.3Mg-0.9Si Alloy

ZENG Yanqi, WANG Feng, XIONG Baiqing, ZHANG Yongan, LI Xiwu, LI Zhihui, LIU Hongwei

2012, 32(3): 1-4.

[Abstract](1924) [PDF 1256KB](395)

Abstract:
The Precipitation hardening behavior of Al4Cu1.3Mg0.9Si during the aging was investigated by hardness measurement, differential scanning calorimetry(DSC) analyses, tensile test and microstructure analyses. The results show that the alloy exhibited a superior precipitation hardening ability. The aging response rate was greatly accelerated with elevating the aging temperature from 160℃ to 220℃, and the peak hardness was remarkably decreased. The major strengthening precipitates of the alloy aging at 190 ℃ was the S phase. After ageing at 190℃ for 24h, the precipitates of the alloy were S phase with a small amount of cubic phase. Comparing with Al4Cu1.3Mg alloy prepared under the same conditions, the Al4Cu1.3Mg－0.9Si alloy exhibited superior tensile strengths at room and elevated temperature.

Investigation of Hydrogen Diffusion in Secondary Hardening Steel by Means of Thermal Desorption Spectrometry

GUO Yunjing, WANG Chunfang, LI Jianxi, WANG Maoqiu

2012, 32(3): 5-9.

[Abstract](1948) [PDF 2257KB](486)

Abstract:
Hydrogen diffusion and its effect on ductility of a secondary hardening steel have been investigated by means of Thermal Desorption Spectrometry (TDS) and slow strain rate tensile tests (SSRT) Results show that the hydrogen diffusion coefficient in the investigated steel is 34210-8cm2s-1, and it is evidently lower than those in usually quenched and tempered martensitic steels, which is presumably due to lots of fine carbides in the steel TDS analysis shows that there are two hydrogen desorption peaks and the desorption activation energy values are 202kJmol-1 and 246kJmol-1 respecitvely, which are caused by weak hydrogen traps such as grain boundaries and dislocations The reduction of area of the SSRT specimen decreased linearly with the hydrogen content When the hydrogen content reached 510-4%, the reduction of area was less than 10%, and the fracture surface was intergranular

Investigation of Interfacial Reaction between High Cr Content Cast Nickel Based Superalloy K4648 and Ceramic Cores

ZHENG Liang, XIAO Chengbo, ZHANG Guoqing, GU Guohong, Li Xin, LIU Xiaoguang, XUE Ming, TANG Dingzhong

2012, 32(3): 10-22.

[Abstract](2175) [PDF 5483KB](419)

Abstract:
The interfacial reaction between alloy and ceramic core in equiaxed and directional solidified high Cr content cast Nibase superalloy K4648 castings was systematically investigated by optical metallography (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA) and Xray diffraction (XRD) The kinetic curve which indicates the relationship between reaction time and amount was illustrated The morphology of reaction interface and the reaction products at different time were also presented The results shown that a severe interfacial reaction occurred between high Cr content cast Nibase superalloy K4648 melt and silicabased core, whereas it did not happened to aluminabased core The inner surface of the casting was destroyed due to the formation of the metallic abnormal knobs during the interface reaction Furthermore, the color of silicabased core changed from the normal white to abnormal black The black reacted region contained some metallic element from the alloy such as Cr, Al and Ti It was noteworthy that the grey region distributed in the black reaction zone after long time reaction The amounts of Cr, Al and Ti in the grey region were much higher than that in the black reacted zone The interfacial reaction between K4648 alloy and silicabased core could be roughly divided into three stages: (1) The (Cr, Al, Ti) rich melts infiltration into ceramic cores (2) The reaction between (Cr, Al, Ti) rich melts and SiO2 matrix in ceramic cores (3) The reaction between (Cr, Al, Ti) rich melts and blocky ZrSiO4 in ceramic cores Partially liquefaction appeared in the ceramic core region during the reaction The main products of interfacial reaction between K4648 alloy and silicabased core were layershape or dendritic Al2O3, blocky intermetallic Cr3Si, ZrO2, (Cr,Zr,Al,Ti) rich oxides, eutectic (Cr,Si,Al,Ti) rich oxides, blocky or dendritic （Ti,Al,Zr,Cr）rich oxides Among these reaction products, the elements Cr, Al and Ti were from the alloy melt and the Zr, Si and O from the ceramic core

Numerical Simulation Researches Influence of Current on Solidification Process Parameters of GH4169 in Electroslag Remelting Process

CHENG Xudong, MIN Jie, MENG Xiaoming, XIANG Hongyu, ZHANG Pu

2012, 32(3): 23-28.

[Abstract](1810) [PDF 2573KB](369)

Abstract:
A series of simulations were made on solidification process parameters changes of GH4169 by using the simulation software MeltFlow in electroslag remelting process Influences of changes of current on solidification process parameters have been analysed It is shown that solidification process parameters decrease gradually with the increase of the current, and the solidification process parameters are not changed when current is 4kA; solidification process parameters decrease gradually with the increase of the cooling rate from the center to edge of remelting ingot, trends of local solidification time, secondary dendrite arm spacing, Rayleigh number are consistent, and these parameters are equivalent in solidification structure judgment; the solidification process parameters differ with the currents which arrives at 4kA; simulation results compares well with the experimental results, the generation and extent of defects could be predicted in different process, the process could be planed and optimized, the qualities of ingot could be improved

Numerical Simulation Researches Influence of Current on Solidification Process Parameters of GH4169 in Electroslag Remelting Process

LIANG Qiang, CHEN Xichun, REN Hao, WANG Fei, GUO Hanjie

2012, 32(3): 29-34.

[Abstract](1873) [PDF 4312KB](385)

Abstract:
A series of simulations were made on solidification process parameters changes of GH4169 by using the simulation software MeltFlow in electroslag remelting process Influences of changes of current on solidification process parameters have been analysed It is shown that solidification process parameters decrease gradually with the increase of the current, and the solidification process parameters are not changed when current is 4kA; solidification process parameters decrease gradually with the increase of the cooling rate from the center to edge of remelting ingot, trends of local solidification time, secondary dendrite arm spacing, Rayleigh number are consistent, and these parameters are equivalent in solidification structure judgment; the solidification process parameters differ with the currents which arrives at 4kA; simulation results compares well with the experimental results, the generation and extent of defects could be predicted in different process, the process could be planed and optimized, the qualities of ingot could be improved

Validation and Simulation for Solidification Process ofTwinRoll Continuous Casting Aluminum Thin Strip

CHEN Shoudong, CHEN Jingchao, LV Lianhao

2012, 32(3): 35-39.

[Abstract](1872) [PDF 1140KB](370)

Abstract:
Based on the solidification of twinroll continuous casting thin strip, the analytical model of heterogeneous nucleation, the amended growth of tip and columnar dendrity transformation to equiaxis dendrity (CET) of twinroll continuous casting thin strip solidification are established by means of the principle of metal solidification and based on the cellular automaton, the emulational model of twinroll continuous casting thin strip solidification is established. Simulated results showed that the grain growth in random preferential growth directions can be described by the model reasonably, and the simulated results were coincident with actual phenomena. Meanwhile has confirmed the mathematical simulation feasibility by using the solidification process of twinroll continuous casting aluminum thin strip.

Constitutive Equations for Hot Deformation of Ti60 High Temperature Titanium Alloy

SUN Erju, BIAN Lihong, LIU Dong, JIAO Yuan, ZHANG Rui

2012, 32(3): 40-45.

[Abstract](1931) [PDF 1929KB](389)

Abstract:
The effects of thermomechanical parameters on the flow stress of Ti60 alloy were investigated based on the results of the isothermal constant strain rate compression tests. The results show that the flow stress of Ti60 alloy reduces with the increasement of temperature and decreasement of strain rate, which presents strong strain rate sensitivity and temperature sensitivity. The constitutive equation of Ti60 alloy was obtained on power function equation and ZH parameter. The results of error analysis show the relative error between the calculated and experimental flow stress is less than 10%. The constitutive equation can describe the flow behavior of Ti60 alloy during hotworking exactly.

Experimental Research on Hot Rolling to Improve TIG Welding Joint Mechanical Properties for AZ31B Magnesium Alloy

LI Xiaoquan, CHU Yajie, YANG Zonghui

2012, 32(3): 46-50.

[Abstract](1913) [PDF 2107KB](333)

Abstract:
To explore method of improving mechanical properties for magnesium alloy welding joint, TIG welding was applied to butt AZ31B magnesium alloy plates with the same composition filled wire, specimens cut from test piece of butt welding were heated up to 350℃ by a special ceramic electric heater, then experiments have been carried out on high temperature tensile machine. Specimens with aswelded and hot rolled were machined as tensile specimens to test normal atmospheric temperature mechanical properties. Meanwhile welding joint was analyzed using optical metallographic microscope and fracture morphology as well as microarea chemical composition were researched with the help of scanning electronic microscopy and energy spectrum analyzer appended. The results show that applying hot rolling procedure, the tensile strength of TIG welding joint can be increased up to 90% of that of the base metal and elongation rate also improved obviously. Hot rolling may effectively change networklike distribution of Mg17Al12 precipitate on Mg grain boundary of weld microstructure and make it solid solve to reprecipitate in way of dispersoidparticle in grain, resulting in dispersionstrengthening effect. In addition, hot rolling may also promote ascast weld microstructure to produce dynamic recrystallization and make microstructure reconstructed and refined.

Analysis of Microstructures and Fatigue Properties of Friction Stir Overlap Welds in AA2024T4 Alloy

XU Xiao, YANG Xin, ZHOU Guang, TOGN Jian

2012, 32(3): 51-56.

[Abstract](1851) [PDF 3341KB](456)

Abstract:
Microstructures and the fatigue performances of AA6061T6 frictionstirwelded overlap joints were investigated. It was shown that the grain deformation of TMAZ was more serious in the retreating side than that in the advancing side. All the fatigue fracture sites of specimens were initiated at the more serious hooking defect, in which the uptrend was larger. When R was equal to 0.1, the fatigue strength k of Aluminum alloy FSW overlap joints was 18.25MPa for the 95% survival probability, which meant an increase of 31.11% as compared with the k=13.92MPa of Aluminum alloy fusion overlap welded joints. Besides, it was observed that the slope value m for the SN curve of the FSW joints was 5.39, which was higher than that of the fusion welded joint set to 3.03.5. So the FSW joint had better fatigue strength than that of the fusion welded joints in the long life region of fatigue performance. Fatigue cracking was initiated at the surface defects or strengthening phase particles locating at the bottom of the upper plate, which were corresponded to the hooking position.

Studies on Shape Memory Hydroepoxy System

WEI Kun, TANG Yusheng, ZHU Guangming, LI Ximin, MEN Qianni, SHI Ruifeng

2012, 32(3): 57-62.

[Abstract](1903) [PDF 1777KB](354)

Abstract:
A novel shape memory hydroepoxy resin system was prepared by hydroepoxy, poly(propylene glycol) diglycidyl ether (PPGDGE) and maleic anhydride (MA) DSC, DMA, bend test and U type shape memory test were used to systematically investigate the thermomechanical, mechanical and shape memory properties of these materials These results indicate that the segment crystallization might occur, due to the existence of long flexible segments between the crosslink points in the hydroepoxy network The glass transition temperature (Tg) of polymer decreases linearly with increasing of PPGDGE content, the highest Tg can reach to 124℃ The novel shape memory hydroepoxy resin has good shape memory performance The recovery time doesnt change dramatically in five cycles, full recovery can be observed only in several minutes, the shape recovery ratio (Rr) is almost 100%

Fabrication of ZnO MSM UV Detector and Its Photoelectronic Property

LIU Dabo

2012, 32(3): 63-67.

[Abstract](1900) [PDF 1280KB](449)

Abstract:
ZnO UV detector were prepared by magnetron sputtering on quartz substrate. The photoelectronic properties of ZnO UV detector was investigated through SEM, XRD, and the detection of photoelectronic properties. It was found that the photocurrent was as much as 3 orders of magnitude greater than the darkcurrent, and the ultraviolet photoresponse was as much as 2 orders of magnitude greater than visible light photoresponse. ZnO UV detector with high sensitivity and visible blind property could be obtained.

Study on Erosion Resistance of Three Stainless Steels Using Solid Particles

WU Xiaomei, SHANG XiaoYu

2012, 32(3): 68-72.

[Abstract](1827) [PDF 1328KB](365)

Abstract:
Erosion resistance of 1Cr17Ni2，1Cr12Ni2W2MoVNb and 1Cr11Ni2W2MoV was evaluated by solid particle erosion testing at 90and 30impact angle. It was found that three stainless steels had been erode under the solid particles impact condition，erosion rate of 30impact angle was higher than erosion rate of 90impact angle. Erosion resistance of three stainless steels was 1Cr17Ni21Cr12Ni2W2MoVNb1Cr11Ni2W2MoV under the same impact condition, 1Cr17Ni2 had the best erosion resistance performance under the Solid Particles impact condition.

Influence of Saline Environment on Fatigue Property of PreCorroded Aluminum Alloy

HUI Li, ZHOU Song, XU Liang, MA Shaohua, WANG Yan, ZHANG Yingying

2012, 32(3): 73-78.

[Abstract](2021) [PDF 1616KB](322)

Abstract:
he influence of saline environment on fatigue property of precorroded 7XXX aluminum alloy were investigated by means of fatigue life experiments of precorroded 7XXX aluminum alloys (Kt=1 and Kt=3) in laboratory air environment and saline environment. The results showed that saline environment significantly reduces fatigue property of precorroded 7XXX aluminum alloy. Laboratory air environment enlarges the dispersivity of fatigue life which becomes larger with the lower stress level. Fatigue life (Kt=1) is little reduced at a high stress level in saline environment and is 22.71% of that in air environment. However, it is significantly deduced at a low stress level in saline environment and is 2.22% of that in air environment. In addtion, fatigue life (Kt=3) is smoothly reduced at different stress level in saline environment

Experimental Study on Crazing Initiation and Damage in PMMA under Creep

WU Guofu, ZHU Xiping, GAO Zongzhan, YUE Zhufeng

2012, 32(3): 79-84.

[Abstract](1849) [PDF 1931KB](353)

Abstract:
A series of creep experiments are carried out for MDYB3 PMMA under different stresses at the room temperature. The whole process from the crazing initiation and growth to specimen's fracture under creep is researched，finding out that the crazing in PMMA present the alternating distribution of sparse and dense ，which is perpendicular to the load. Based on the experimental data and analysis，a relationship between stress and the time of the crazing initiation is given，which quantifies the crazing initiation time shortened nonlinear as the stress increases. And a model is built to describe the crazing damage density with stress and time for MDYB3 PMMA using of nonlinear fitting based on hyperbolic function.

Study on TensionTension Fatigue Properties of T700 Composite Laminates

WANG Jun, CHENG Xiaoquan, ZHANG Jikui, LI Zhengneng

2012, 32(3): 85-90.

[Abstract](2071) [PDF 1079KB](442)

Abstract:
Tensiontension fatigue test was carried out on T700/9368 composite smooth laminates and those with a hole of different diameter The stiffness attenuation of the specimens was measured while bearing fatigue load and the fatigue damage mechanism of T700/9368 composite laminates was explored by ultrasonic Cscan  The damage model of the laminates was established according to the Means of Elasticity Modulus Based on average stress criterion, the damage model of the laminates with holes was established as well The experimental data was fit into the fatigue damage model with leastsquares method, to obtain a specific formula for calculating the fatigue life of T700/9368 laminates Applying this formula to predict fatigue life of laminates under several different stress levels, the results are in a good agreement with experimental data

Application of Infrared Thermography in Research of Radar Absorbing Coating Defects

WANG Zhiyong, LIU Yingtao, WANG Xiaohu, ZHANG Tong, LI YanhongHUO Yan

2012, 32(3): 91-95.

[Abstract](1778) [PDF 1383KB](397)

Abstract:
A NDT method of bonding defects in radar absorbing materials is developed with the infrared thermograph technique. Radar absorbing film and radar absorbing coating samples with different bonding defects are prepared on aluminum-alloy bases. The infrared thermograph testing system is used to detect cooling behavior of a sample surface after it has been heated from a flash lamp array. Thermal properties of a defect or its host material are analyzed by IR photos and temperature datas. It is shown that bonding defects in RAC can be found using this method, which is convenient, accurate and nondestructive for coatings. The method makes it possible to control RAC quality during RAC application and RAC reliability in service.

Diagnosing Compress Damage in Carbon Fabric/EpoxyMatrix Composites by Electrical Resistance Measurement

XIE Xiaolin, HONG Zhen, LI Zhipeng, QUAN Hongying, FAN Hongqing

2012, 32(3): 96-100.

[Abstract](1873) [PDF 963KB](317)

Abstract:
The influence of compress load on different specification carbon fabric/epoxymatrix composites was studied by electrical resistance measurement and acoustic emission technology, compress damage in composites was diagnosed by electrical resistance measurement. The experiment results showed that when carbon fabric/epoxymatrix composites were compressed, the conductive network in composites changed, so, electrical resistance of composites changed too. At the same time, acoustic emission energy of composites increased. When the change extent of electrical resistance of composites exceeded a certain value, compress damage in composites can be diagnosed. The safety of composites in use can be improved in this case.

2012 Vol. 32, No. 3