航空材料学报

2014, 34(5): .

[Abstract](949) [PDF 3723KB](64)

Abstract:

Effect of Solution-ageing on Microstructure and Properties of Ti-5Mo-5V-2Cr-3Al Titanium Alloy

WEI Yan-guang, TAO Hai-ming, LUO Zheng, CUI Xue-fei

2014, 34(5): 1-6.

[Abstract](1385) [PDF 4944KB](106)

Abstract:
The tensile fracture morphology and microstructure of the 10mm bars of Ti-5Mo-5V-2Cr-3Al titanium alloy were analyzed under different solution-ageing conditions, and the effects of which on mechanical properties were studied. The results show that when the alloy is heated below the transition point, primary decreases and grain increases with the increase of solution temperature. Consequently, the fibrous zone in fracture morphology decreases and the dimple becomes big but shallow. Ways of fracture change from dimple to quasi-cleavage with the increase of strength and decrease of plasticity. Moreover, when the alloy is heated above the transition point, primary disappears and grain re-nucleates and grows. The fracture is made up of small crystal planes with clear edges, which suggests that the alloy fracture is typical intergranular brittle fracture with the strength over 1500/MPa and elongation 2%.

Effect of Forging Process on Abnormal Grain Growth of FGH96 Superalloy

YANG Jie, WANG Xiao-feng, JI Chuan-bo, ZOU Jin-wen

2014, 34(5): 7-11.

[Abstract](1397) [PDF 2873KB](132)

Abstract:
Based on the compression experiments of FGH96 Double Cone (DC) specimens and circular cylinder specimens, the effect of forging temperature, strain rate and strain on Abnormal Grain Growth (AGG) was examined, and isothermal compression of DC specimens was simulated with finite element method (FEM). The critical process parameters are determined within temperature 960℃-1060℃ and strain rates 0.0032s-1-0.032s-1 based on the compression of DC specimens. It is found that AGG does not occur within the strain range 0.03-0.2 at 1040℃ with the crosshead speed of 0.1mm/s. A FEM model is developed for FGH96 superalloy and DC specimen compression is simulated. The strain distribution in the cross section of compression DC specimen is obtained by simulating, which corresponds to the grains distribution from experiment.

Effect of High Temperature Long-term Aging on Tensile Alloy and Stress Rupture Properties of a Nickel Base Single Crystal Alloy

SHUI Li, HU Zhuang-qi

2014, 34(5): 12-16.

[Abstract](1234) [PDF 2076KB](114)

Abstract:
The influences of high temperature long-term aging on the tensile strength at room temperature and stress rupture property at 950℃/240MPa were investigated for a new nickel base single crystal alloy. The results show that the tensile strength of specimens after aging at 1000℃ for no more than 500h does not significantly decline, whereas the tensile yield strength greatly reduces compared with standard heat treatment specimens. The tensile strength continuously declines with the increasing for the aging specimens more than 1000h. Meanwhile, the stress rupture lives of specimens after aging 1000h decreases substantially and the elongation rises rapidly. Furthermore, the stress rupture lives decline slowly and elongation is tending towards stability. The change of the ' morphology and disappearance of the /' interfacial dislocation net are the main reasons for the decrease of mechanical properties of the high temperature long-term aging specimens.

Effects of Minor Erbium on Microstructure and Mechanical Properties of Al-Mg-Mn Alloy

ZHANG Jin-wu, BAI Pu-cun, HOU Xiao-hu, LI Bo

2014, 34(5): 17-24.

[Abstract](1395) [PDF 6762KB](96)

Abstract:
Both Al-6.8 Mg-0.3Mn and Al-6.8Mg-0.3Mn-0.4Er (mass fraction/%) alloy ingots were prepared with semi-continuous casting process, and the alloy ingots were rolled into 4mm thick sheets after homogenization treatment and multipass hot rolling. The effect of Er on microstructure and mechanical properties of Al-Mg-Mn alloy sheets at different annealing temperatures were investigated. The results show that the addition of minor Er can improve the strength of the Al-Mg-Mn alloy significantly as well as the coordination between strength and plasticity of the alloy. Besides, the ability of anti-recrystallization and mechanical properties at room temperature are largely enhanced. Finally by annealing at 300℃ for 1h, the Al-Mg-Mn-Er alloy sheet obtains the optimum application values of b, s and , which are 421MPa, 310MPa and 18.3% respectively.

Recrystallization of Oxide Dispersion Strengthened MGH956 Cold Rolled Sheet

TIAN Yun, YANG Zheng, LIU Guang-zu

2014, 34(5): 25-36.

[Abstract](1274) [PDF 9143KB](86)

Abstract:
Recrystallization behaviors of oxide dispersion strengthened MGH956 cold rolled sheet that are able to form two kinds of entirely different crystal grain structure,rather uniformly fine and extremely coarse,were investigated. Microstructures of cold rolled sheets isothermally annealed at 700~1350℃ for 1~120min were examined by optical microscopy. Results show that recrystallization initial and finish temperatures, onset nucleation sites, and grain growing speeds of the two kinds of grain structure are obviously different, which indicates that recrystallization formation mechanism of MGH956 cold rolled sheet is not merely by one, but at least by two models, and they are able to occur jointly within one sheet. All of those result in diversity on structure morphologies and extreme differences on grain size of MGH956 sheet recrystallized.

Influence of Bias Voltage on Microstructure and Properties of Magnetron Sputtering TiB₂ Coating

GU Wen-cui, LI Shou-de, WANG Huai-yong, CHEN Chun-li, LI Peng, HUANG Feng

2014, 34(5): 37-42.

[Abstract](1419) [PDF 1653KB](114)

Abstract:
In order to improve the compactness of TiB2 coating, the samples with different substrate bias (floating, -30V and -90V) have been deposited by non-reactively magnetron sputtering. The microstructure was analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The nanoindentation, Vickers indentation and wear tests were used to characterize the mechanical properties. The results show that only hexagonal TiB2 crystalline can be identified from all of the coatings. The hardness of coating under floating is lower (~15GPa) with loose columnar structure. With the increase of bias voltage, the columnar structures are found to be compact and even disappear, and the hardness and tear-resistant property of which enhance. When the bias voltage increases from -30V to -90V, the size of crystal grain grows by one time to 21nm with the improvement of hardness from 35.5GPa to 61.9GPa. The columnar structure becomes compact and finally disappears. Simultaneously, the wear rate is reduced to 5.6 10-16m3/Nm, when the coating is subjected to the sliding test against Al2O3 ball, one order of magnitude lower than that of the coating deposited at -30V bias.

Electrical Insulating Properties of Plasma Sprayed Al₂O₃ Coating

GUO Rui, LIANG Bo, ZHAO Xiao-bing, YANG Ying-chun, JL Heng, ZHENG Xue-bin

2014, 34(5): 43-48.

[Abstract](1236) [PDF 2887KB](77)

Abstract:
Al2O3 insulation coating was deposited by atmospheric plasma spraying (APS) method on Cu substrate. The microstructures of the Al2O3 coating were characterized by XRD and SEM. Based on the investigation of the influences of porosity and moisture absorption behavior on insulation performances, the relationship between the structure of plasma spraying Al2O3 coating and property of electric insulation failure was analyzed. Results show that the as-sprayed Al2O3 coating has dense structure and good interface bonding between the Al2O3 coating and substrate, whose porosity changes in the range of 5% to 7% as coating thickness varies. The breakdown of as-sprayed coating always occurs at the position of the hole, which demonstrates a typical morphology of corona breakdown. The cracks resulted from corona breakdown prolongates along the direction of the breakdown are formed as a tunnel. The direction of breakdown is closely related with the position of holes not the electrode polarity. There is a reciprocal function relation between coating thickness and breakdown strength of the coating. The formation of the conductive path caused by moisture absorption results in decrease of the insulate property of as-sprayed coating.

Microstructure Evolution and Refinement Mechanism of Ultra-fine Copper Prepared by Asymmetrical Accumulative Roll Bonding

ZHOU Lei, SHI Qing-nan, WANG Jun-li

2014, 34(5): 49-54.

[Abstract](1227) [PDF 3991KB](215)

Abstract:
The microstructure and grain boundaries of the copper prepared by Asymmetrical Accumulative Roll Bonding(AARB) within 1 to 3 passes were studied, and the grain refinement mechanism of AARB was obtained. The results show that S-band is obtained in AARB process. The S-band parted by the consecutive dislocation walls crosses inside, and the ultra-fine copper with sub-grains is prepared. Sub-grain boundaries with low-angle are obtained in the refine process of AARB. And with the shear stress,these discontinuous low-angle boundaries are combined as the sub-grain boundaries.

Nonisothermal Crystallization Kinetics of Polypropylene Nano-diamond as Fillers

CAO Xin-xin, LUO Si-hai, WANG You, HE Xiao-fang

2014, 34(5): 55-62.

[Abstract](1257) [PDF 3956KB](107)

Abstract:
Effeets of Nano-diamond composites on the crystal morphology and non-isothermal crystallization of linear low density polyethylene(LLLDPE) were investigated by XRD, polarization microscope(POM) and differential scanning calorimetry(DSC). The Jeziorny and Mo methods were applied to the analysis of the non-isothermal crystallization kinetics of LLDPE and LLDPE/ Nano-diamond composites, and the activation energy (E) based on Kissinger method was evaluated. The results show that Nano-diamond is an effective nucleating agent, provides more activated nuclei for the crystallization of LLDPE, plays a role in heterogeneous nucleation, and enhances crystallization onset temperature(To), crystallization peak temperature(Tp) and crystallization rate. Additionally, the spherulites become smaller and more homogeneous. Nano-diamond decreases the activation energy of LLDPE, while it reaches a minimum at 1%.

Effect of Convection Heating on Mechanical Behavior of ZrO₂-8%Y₂O₃ Coat the System

CHEN Yu-hui, YANG Xiao-xiang, ZHONG Shun-cong

2014, 34(5): 63-68.

[Abstract](1207) [PDF 2038KB](141)

Abstract:
To study the mechanical behavior of plasma spraying ZrO2-8% (mass fraction) Y2O3 coating system in the process of convective heat transfer, the paper analyzed the thermal barrier coating of turbine blade and presented simulation on the coating and process of heat transfer. The study was achieved by combining heat transfer theory and thermal-mechanical finite element method. The results indicate that residual stress grows with the increase of heat transfer coefficient of coating surface. Findings also show that the maximum residual stress value increases first and then decreases, with the increase of heating rate when the heat transfer coefficient is fixed and heating rate changed. The research suggests some references to the choice of heat transfer coefficient and heating rate which are provided with reasonable areas.

Numerical Study of Thermal Insulation Properties of Thermal Barrier Coating Based on Columnar Structure

LING Xi-xiang, WANG Yu-zhang, WANG Xing

2014, 34(5): 69-74.

[Abstract](1353) [PDF 2725KB](103)

Abstract:
To study the effects of pore micro-structure of columnar thermal barrier coating on its thermal insulation properties, software for constructing coating microstructure and analyzing thermal insulation properties were developed by combining the methods of quartet structure generation set (QSGS) and thermal resistance network. Based on this, anisotropy pore microstructure of columnar coating was also constructed. This paper focused on the impact of columnar pore sizes, number and thickness on effective thermal conductivity and thermal insulation properties of the coating. The results show that increasing the porosity of the coating is an effective way to enhance thermal insulation properties of the coating. When porosity is constant, as the columnar pores diameter decreases, its thermal insulation properties are enhanced, and the structure is more stable. When porosity is constant, as columnar pores elongate, its thermal insulation properties are weakened to some extent, but the steady-state temperature distribution is more uniform, the structure is more stable.

Anti-corrosion Type Radar Absorbing Coating

QI Yu, HE Shan, SHI You-qiang

2014, 34(5): 75-80.

[Abstract](1417) [PDF 1976KB](122)

Abstract:
We prepared anti-corrosion type two-layer broadband radar absorbing coating, through electrical properties design of absorbing materials, optimal selection of absorbent and recipe verification. When this coating had a thickness of 1.7mm and surface density of 4.0kg/m2, its reflectivity was less than 11.0dB in the range of 8 to 18GHz. After high/low temperature-resistant, seawater-resistant and damp and hot-resistant tests, no obvious changes appear from the coating, reflectivity and adhesive force. The study indicates that the absorbing coating is suitable in marine environment.

A Method to Evaluate Bearing Strength and Stiffness of Composite Joints

LIU Xiang-dong, LI Ya-zhi, SU Jie, DING Rui-xiang

2014, 34(5): 81-87.

[Abstract](1381) [PDF 2116KB](106)

Abstract:
Mechanical strength of single-bolted composite joints was investigated using cumulative damage technique. Aware that the residual bearing stiffness of a joint may vary after the occurrence of pin-hole bearing damage.The stiffness modification technique put forward in this paper states that the moduli of the material related to fiber and matrix compression failure in bearing zone are subjected to a sudden drop and then raising gradually. The results to apply the laws of material properties (modulus) vary with the compressive strains after matrix and fiber compression failure in pin-hole bearing area attained to predict joint strength and stiffness behavior, are just in good agreement with the test results.

Research on Ultrasonic Back-wall Echo Monitoring Method for Radial-axial Crack of Aircraft Engine Disk

YANG Ping-hua, LIANG Jing, WANG Zheng, GAO Xiang-xi

2014, 34(5): 88-92.

[Abstract](1357) [PDF 2564KB](96)

Abstract:
Experiments were performed by focusing and flat probes with different focus lengths and frequencies under the incidence angles of ultrasonic beam 0, 1, 2and 3 respectively. Based on the optimization of the incidence angle as well as probe parameters, an ultrasonic back-wall echo monitoring method was established for the detection of radial-axial crack of aircraft engine disk. The research reveals that in contrast with the normally incident wave beam, performing the ultrasonic back-wall echo monitoring method with a small angle incidence longitudinal wave can enhance the sensitivity of ultrasonic evaluation of cracks. The optimal results can be obtained by using a 10MHz ultrasonic focusing probe with the focus length of 89mm and incidence angle of 2. The experiments show good agreements with the numerical simulation results. The study results are the great reference values to the application of ultrasonic back-wall echo monitoring method for the evaluation of radial-axial cracks.

Research Progress in Multi-spectrum Compatible Stealth Materials

CHENG Hong-fei, HUANG Da-qing

2014, 34(5): 93-99.

[Abstract](1693) [PDF 1370KB](169)

Abstract:
Based on the specific research and application background, the multi-spectrum compatible stealth material is introduced. This paper makes a review on its technology development both at home and abroad in the areas of infrared/radar, infrared/visible light and infrared/laser compatible stealth materials. Besides, the paper introduces the research achievements and progress of multi-spectrum compatible stealth materials in hot spot areas, such as doped oxide semiconductor and photonic crystal. Also, its development direction and focus are pointed out.

2014 Vol. 34, No. 5