航空材料学报

2013, 33(5): .

[Abstract](943) [PDF 13524KB](69)

Abstract:

Hot Deformation Behavior of Powder Metallurgical TiAl Alloy

LIU Na, LI Zhou, YUAN Hua, XU Wen-yong, ZHANG Yong, ZHANG Guo-qing

2013, 33(5): 1-5.

[Abstract](1158) [PDF 1082KB](117)

Abstract:
Hot deformation behavior of powder metallurgical TiAl alloy was investigated on Gleeble-3500 thermal mechanical simulator at a temperature range of 1050-1200℃, and a strain rates range of 0.001-0.1s-1 with engineering strain of 50%. The results show that, the flow stress of PM TiAl alloy is sensitive to both deformation temperature and strain rate, significantly decreasing with the increase of deformation temperature and the decrease of strain rate. Dynamic recrystalization occurs during the hot compression. The flow stress model of TiAl alloy during hot compression was established based on the Arrhenius equations and Zener-Hollomom parameter, the regressed expression is =90.91In{(Z/1.681016)1/2.06+[(Z/1.681016)2/2.06+1]1/2}. The hot deformation activation energy of PM TiAl alloy was calculated about 477.56kJ/mol. And the flow stress constitutive model can efficiently predict the deformation behavior of the PM TiAl alloy during high temperature deformation.

Experimental Research on Formation and Evolution Process of Third Body of ZDPH Low Alloy Steel

LI Zhi-qiang, HAN Jian-min, LI Wei-jing, PAN Li-ke, YANG Zhi-yong

2013, 33(5): 6-12.

[Abstract](1727) [PDF 3300KB](108)

Abstract:
During the friction process, the two-body friction system is changed into three-body system by the third body which formatted on the surface of the friction material. The formation and evolution of third body plays an important role to the friction and wear properties of materials. 10 tests with different friction time which is from 1 to 10 minutes were carried out by using ZDPH low alloy steel and copper matrix powder metallurgy. The result shows that the third body appears on the surface at certain speed and pressure. During friction process, the friction surface is covered by the third body which tends to be more consistent and flattened. Third body is the mixture of the friction materials particles and their oxides. With the high pressure and temperature, the third body on the surface experiences a dynamic process of forming and destroying. Oxidized spots, adhesive particles, adhesive pits, surface peeling and material transfer can be observed on it. And the micro-hardness of the third body is higher than the hardness of friction material.

Effects of Surface Integrity of Shot Peening, Grit Blasting and HVOF Sprayed WC-17Co Coating on Fatigue Properties of TC18 Titanium Alloy

DU Dong-xing, LIU Dao-xin, MENG Bao-li, ZHANG Xiao-hua

2013, 33(5): 13-21.

[Abstract](1337) [PDF 5845KB](133)

Abstract:
In order to investigate the effect of surface integrity of shot peening(SP), grit blasting(GB) and HVOF sprayed WC-17Co coating on the fatigue behavior of Ti5Al5Mo5V1Cr1Fe(TC18)alloy, the surface integrity of the surface treatment was evaluated by using X-ray diffraction (XRD), surface roughness meter, microscopic hardness tester, scanning electron microscopy (SEM) and X-ray stress test instrument. The fatigue property of TC18 alloy influenced by above surface treatment was studied by using rotating bending fatigue test machine. The result indicates that the surface integrity after SP treatment is better than that after GB process. Therefore, the fatigue life of TC18 titanium alloy increases dramatically by SP, but there is no significant change of fatigue life by GB treated TC18 alloy. The fatigue life of HVOF WC-17Co coated TC18 alloy with SP pretreatment is increased six times larger than that of the alloy substrate. This is attributed to the retained large residual compressive stress in the SP layer. The crack initiation and earlier propagation are delayed by the residual compressive stress. However, the fatigue life of HVOF WC-17Co coated TC18 alloy with GB pretreatment is obviously decreased. This is due to the low toughness, large surface roughness, and pore defects of WC-17Co coating. The relaxation of residual compressive stress influenced by the HVOF high temperature process and the notch effect in GB layer are also the reasons.

Experimental Investigation of Hot Deep Drawability of EW94 Heat Resistant Alloy Sheet

LI Li, ZHOU Nan

2013, 33(5): 22-28.

[Abstract](1231) [PDF 2570KB](133)

Abstract:
Mechanical properties and hot deep drawability of EW94 alloy sheet prepared through hot-rolling process was systematically investiaged. For this purpose, uniaxial tensile tests were conducted to investigate mechanical properties, strain rate sensitivity parameter (m-value) and plastic strain ratio (R-value) of the sheet at elevated temperatures. The sheet exhibited the high strength of more than 300 MPa at 513 K and superplasticity above 723 K. The m-value and R-value ranged from 0.07-0.32 and 0.9-1.4 respectively. Non-isothermal deep drawing tests were performed to explore the influence of technological parameters on deep drawability for EW94 sheet and AZ31 sheet. Limiting drawing ratio (LDR) of EW94 sheet reached 5.2 that is much higher than that of AZ31. Textures of the initial sheet and the necking regions for post-deformed cylindrical cups were measured. It is suggested from texture analysis that the activation of pyramidal slip systems made contribution to neck of the cup wall. The excellent LDR of EW94 sheet is attributable to its relatively stronger temperature sensitivity of flow stress.

Microstructure and Mechanical Properties of Aluminum Alloy 2618 Prepared with New Thermomechanical Treatment

WU Bo, ZHAO Man-xiu, LIU Ting-ting, SU Xu-ping, WU Chang-jun, WANG Jian-hua

2013, 33(5): 29-35.

[Abstract](1351) [PDF 3367KB](102)

Abstract:
Aluminum alloy 2618 was prepared by three procedures. The three procedures are as follows: (1) solution treatment + peak aging treatment (T6), (2) solution treatment + ECAP+ peak aging treatment, (3) solution treatment + ECAP + short time recrystallization + peak aging treatment. The grain microstructures and mechanical properties of the alloys were investigated by using optical microscope and tensile testing machine, respectively. The results indicated that the grain microstructure of alloy 2618 prepared with solution treatment + ECAP + short time recrystallization + peak aging treatment was refined remarkably and the comprehensive mechanical properties of the alloy was enhanced effectively. The new thermomechanical treatment is a kind of effective method in improving the strength and toughness of aluminum alloy 2618.

Temperature Fields in 6082 Aluminum Alloy Samples Bobbin-Tool Friction Stir Welded

LI Jing-yong, ZHOU Xiao-ping, DONG Chun-lin, DONG Ji-hong

2013, 33(5): 36-40.

[Abstract](1436) [PDF 3032KB](239)

Abstract:
By applying thermocouple temperature measurement technology, the temperature curves of feature points in 6082 aluminum alloy samples bobbin-tool friction stir welded were measured, and then the characteristic of temperature distributions in different areas of welding samples were analyzed. More heat is created during bobbin-tool friction stir welding (BTFSW) because of the double shoulders, and very different heat elimination conditions compared with traditional friction stir welding (FSW). So the faster welding speeds were applied during bobbin-tool friction stir welding led the obvious differences between the temperature distributions of BTFSW samples and that of FSW samples. The BTFSW process is divided into the acceleration stage and stable stage. At the first stage, the temperature near the beginning end of samples increased slowly along with the welding speed rising. While the welding speed reached the stable data, 400mm/min, the temperature of the subsequent feature points increased rapidly to the peak temperature while the tool arrived near them. Under the same welding condition, the temperature near the lower shoulder is higher than that near the upper shoulder, and the temperature at retreating side is higher than that at advancing side. Increasing welding speed, the peak temperature of each measurement point is lower and lower. With the temperature measuring point away from the weld center, the effect of welding speed on the temperature distributions is gradually weakened.

Experimental Study of Steady Electric Field on Refining Solidification Microstructures of Ti-50at%Al Binary Alloy

ZHANG Yong, DING Hong-sheng, LIU Jun, YU Zhong-jun, LIU Hong-hui

2013, 33(5): 41-45.

[Abstract](1214) [PDF 1982KB](125)

Abstract:
By utilizing electric field solidifying technology, the Ti-50at%Al binary alloy was treat to a steady electric field in its mush zone and above its liquidus. The effects of electric field on morphologies of phase and /2 laminar were analyzed through comparing different current densities. Results show that steady electric field makes the most significant difference in refining solidification microstructures of Ti-50at%Al nearby electrodes. Furthermore, with the increasing current density, the grains of alloy decrease gradually.

Effect of Milling Steel Ball Ratio on Microwave Absorbing Properties of Flake Carbonyl Iron

LI Xiao-guang, LV Hua-liang, JI Guang-bin, ZHANG Bao-shan, TANG Dong-ming

2013, 33(5): 46-53.

[Abstract](1381) [PDF 3791KB](183)

Abstract:
The behaviours about high saturation magnetization and certain plane anisotropy of flake-shaped carbonyl-iron particle (FCI) are conditioned by the breakthrough mechanism of Snoek limitation. Thus, it will be exposed a wide application for the field of microwave-absorb. The FCI was synthesed from spherical carbonyl iron powder with various steel ball ratios by mechanical milling. The results have also demonstrated an obvious effect on the morphological and electromagnetic characteristics accompanied with different ratio of steel ball. With the decrease of average diameter of the steel ball, the flake product yield was gradually increased with the larger size, thinner flake and the increased absorbing properties. For the milling with diameter of 4 mm, the FCI has the best microwave absorbing properties, and the real part and the imaginary part of complex permeability of the material at 2 GHz can be achieved 2.8773 and 0.9493 respectively. The results also show that the reflectance loss (RL) reached the maximum value of -35.472 dB at 9.184 GHz when the coating thickness is 2 mm, and the frequency band is 7.429 GHz when the RL is less than -10 dB.

Electromagnetic Properties of Co and Co/Fe Coated MWCNTs before and after Heat Treatment

DING He-yan

2013, 33(5): 54-60.

[Abstract](1219) [PDF 1658KB](124)

Abstract:
Multi-walled carbon nanotubes (MWCNTs) coated with Co and Co-Fe alloy ferromagnetic material is an ideal kind of light electromagnetic wave absorber.In this article, the influence of heat treatment on the electromagnetic properties of Co and Co-Fe coated MWCNTs was discussed. The surface composition and structure of Co and Co-Fe coated MWCNTs was characterized by field emission scanning electron microscope (FESEM), energy dispersive X-ray detector (EDX), X-ray diffractometer (XRD). Its electromagnetic properties were also measured. The results showed that the microwave absorbing property of Co and Co-Fe alloy coated MWCNTs in high frequencies was improved and the saturation magnetization increased while the coercivity decreased after heat treatment.

Influence of CaCO₃ on Electrical Properties of Carbon Black/Epoxy Composites

ZHENG Xing-zhuo, JI Tie-zheng, ZHANG Jiao-qiang, YANG Jian-feng, LI Ping, GU Jing-kai

2013, 33(5): 61-65.

[Abstract](1244) [PDF 1607KB](169)

Abstract:
This paper studies the influnce of CaCO3 content on the room volume resistivity and resistance-temperature characteristics of CB/EP composite. With CaCO3 as additional agent,carbon black (CB) as conductive filler,epoxy resin (EP) as matrix resin,2-ethyl-4-methyl-imidazo(2,4-EMI) as curing agent,the CO3/CB/EP composites were prepared by ultrasonic dispersion. Its room volume temperature resistance and volume resistance-temperature characteristics were tested, morphology properties were analyzed by scanning electron microscopy. The results show that, in the system of CaCO3/CB/EP which CB content is 14%,with increase of CaCO3 content,the room volume temperature volume resistivity of the composites decreases and then increases. The volume resistivity reaches minimum at a ration of 0.5:1 (CaCO3:CB). The PTC (Positive temperature coefficient) effect of the CaCO3/CB/EP composite material is stronger than that of EP/CB composite material, and it has no NTC (Negative temperature coefficient) effect within the test temperature.

Structure and Performance of OMMT/Hydrogenated Nitrile Rubber Nano-Composite Material

ZHANG Chun-mei, DU Hua-tai, PANG Ming-lei, ZHANG Zhi-gang, CUI Yu, DU Ming-xin, ZHANG Hong-min, CHEN Bin

2013, 33(5): 66-71.

[Abstract](1195) [PDF 1544KB](166)

Abstract:
Hydrogenated nitrile rubber (HNBR)/organic montmorillonite (OMMT) nano-composites was prepared using melt intercalation preparation. And the amount of organic montmorillonite (OMMT) were 0 phr, 5 phr, 10 phr, 15 phr, 20 phr respectively. This paper examines the effect of the OMMT amount on the mechanical properties and ablation performance, and we analysis the ablative carbon layer morphology and composition of the nanocomposite. The results show that OMMT have a reinforcing role in a certain range (0phr ~ 15phr). But it can not improve of the strength and elongation when its content is too much (20phr). In the experimental range, with the increase of its content, ultimate permanent deformation and hardness of the materials increases, and its elastic resilience reduce in turn. The linear ablation rate and the mass ablation rate is generally a downward trend. The mechanical melt mixing process makes the span of montmorillonite lamella change, and the lamella structure is completely destroyed after ablation. The composite positive and negative structure of carbon layer formed in ablation is dirrerent obviously.

Probabilistic Analysis Method and Sub-cluster Theory Model of Delamination for Composite Components

WANG Xue-ming, XIE Fu-yuan

2013, 33(5): 72-76.

[Abstract](1187) [PDF 831KB](112)

Abstract:
Aimed to that the of delamination is easily appeared in composites during autoclave process, this study focuses on proposing and developing the probabilistic analysis method and sub-cluster theory model of delamination for composite components in order to evaluate quantitatively the process quality of composite components with different shape. Some quantitative results of the relative acceptable rate of delamination and the sub-cluster parameters reflecting the tendency of delamination area are obtained. The results indicate that a good agreement is observed between these two statistical methods for evaluating process quality of composite components. The more complicated shape of composite components, the higher tendency of the large delamination area appearance and the lower relative acceptable rate of delamination. The results provide important theoretical analysis methods for evaluating process quality of composite components.

Influence Law of Pre-Corrosion on AF1410 Steel Fatigue Life

HAO Xue-long, ZHANG Dong-hui, LIU Jian-hua, SUN Ze-ming

2013, 33(5): 77-82.

[Abstract](1215) [PDF 885KB](113)

Abstract:
The different time pre-corrosion was applied to the AF1410 ultra-high-strength steel by using the neutral salt spray, and the fatigue test with different loads was carried out to the pre-corrosioned specimens. The pre-corrosion fatigue life was studied, and the S-N curve showing the pre corrosion fatigue life of the material was obtained. The curve of C, which was the influence coefficient of the pre-corrosion time on the AF1410 steel fatigue life, was presented and fitted. The pre-corrosion fatigue life data for the different pre-corrosion time and under the different fatigue loading were analysed comprehensively, and surface of C-T-S, which denoting the influences of the pre-corrosion time and the fatigue load on the pre-corrosion fatigue life, was obtained. Thus the fitting formula describing the influences of the pre-corrosion damage on the fatigure life was established, and the dymamics law for the impact of pre-corrosion on the AF1410 steel fatigue life was investigated.

Research Progress and Review on Key Problems of Stress and Failure Mechanism of Thermal Barrier Coating

HAN Meng, HUANG Ji-hua, CHEN Shu-hai

2013, 33(5): 83-98.

[Abstract](1322) [PDF 3707KB](296)

Abstract:
The research of failure behavior and stress in failure process of thermal barrier coating is always emphazed in studying the failure of thermal barrier coating. On the base of review of the current state of numerical simulation of stress, three key issues of thermally grown oxide, nonlinear characteristics of materials, internal relations between stress state and failure mechanism were reviewed in this paper. The questions of the influence on internal stress and failure mode of the coating system through the formation of thermally grown oxide and the stress relief mechanism of the creep characteristics of coating were discussed separately. At last, on the basis of the results of numerical simulation and the results of experimental observation, the failure modes of thermal barrier coating made by APS/EBPVD were comparative summarized. In the last part of present paper, the development bottleneck of the traditional 8YSZ TBC was described. In the future, the research will be more focused on exploring new ceramics with lower thermal conductivity, and exploring reasonable structure of the coating. The new coating system (the double-ceramic-layer thermal barrier coating) was introduced and discussed. The numerical simulation is still an important approach in studying the stress state and failure behavior of the new coating, and also in optimizing the structure of the coating.

2013 Vol. 33, No. 5