航空材料学报

2018-01-Catalog

2018, 38(1): .

[Abstract](1431) [PDF 887KB](25)

Abstract:

Progress in Amorphous Transparent Conducting Oxide Thin Films

Xiaofeng ZHANG, Yue YAN, Mu CHEN, Hongyan LIU, Changshan HAO, Guanli ZHANG

2018, 38(1): 1-16.

[Abstract](4644) [FullText HTML] (1650) [PDF 5399KB](108)

Abstract:
With the increasing wide application of organic or polymer substrates, amorphous transparent conducting oxides (a-TCOs) had been widely applied to thin-film transistors, polymer/organic solar cells, electrochromic devices, electromagnetic shielding and other areas due to the combined transparency and conductivity as well as stable properties, processing compatibilities with current technologies and free of post-annealing. A-TCOs films were not the amorphous counterpart of crystalline TCOs but prepared with special elements under certain conditions. After the brief introduction to the working principle of TCO, the even general amorphous transparent semiconducting oxide was addressed intensively. It was worth to note that compared with c-TCOs and classic silicon, the features of electronic structure of a-TCOs were the cations with special configuration (n-1)d¹⁰ns⁰. The stable amorphous structure and excellent properties can be conserved due to larger overlap integral between the adjacent atoms, high mobility and robustness. Particularly, the near range structure characterization such as the medium range order, band structure described by density of states and the metastability of amorphous structure and the related properties were introduced as well. Afterwards, the properties and features of N-type and P-type a-TCOs were exampled in details, especially the indium-based systems, such as excellent a-In-Zn-O films. Less example of P-type a-TCOs were shown as no general principle had been formed for that. Finally, many state-of-art applications including thin-film transistor are introduced. Based upon the current status and emerging trend, three potential research perspective directions of a-TCO have been delivered:(1) to further investigate non-indium based a-TCO; (2) to develop on the P-type TCO with novel principle and material systems; (3) to enable the alternative application that occupied by conventional silicon previously.

Research Progress on Measurement Methods and Influence Factors of Thin-film Stress

Yibo MA, Mu CHEN, Yue YAN, Weiming LIU, Youxiu WEI, Xiaofeng ZHANG, Jiaming LI

2018, 38(1): 17-25.

[Abstract](3748) [FullText HTML] (1527) [PDF 1368KB](141)

Abstract:
With the size of thin-film electronic devices decreasing, the film stress became an important reason for the failure of thin film devices. Film stress not only affected the membrane structure, but also associated with film optics, electricity, mechanics and other properties, therefore film stress turned into one hot spot in the research field of thin-film materials. This paper reviewed the latest research progress of film stress, substrate curvature method, X-ray diffraction technique and Raman spectroscopy, several frequently used stress measuring techniques were compared and analyzed, and composition ratios of thin film, substrate types, magnetron sputtering process parameters (sputtering power, work pressure, substrate temperature) and annealing etc. factors influencing thin film stress were summarized. It was found that substrate curvature method was suitable for measuring almost all kinds of thin film materials. X-ray diffraction and Raman spectroscopy were just fit for measuring materials with characteristic peaks. Nanoindentation method required extra stress-free samples as comparison experiments. During film fabrication and annealing process, film stress usually transited from compressive to tensile status, and several factors combined together could affect stress, so film stress could be reached the minimum value or even stress-free status through setting appropriate parameters. Finally, combined with film stress research status, accurate stress measurement methods for different materials as a thin-film stress research direction were introduced, and challenges in thin film detection range were pointed out.

Unified Constitutive Model and Numerical Implementation of NiTi Alloy Involving Phase Transformation and Plasticity

Yunfei LI, Cheng CHEN, Xiangguo ZENG

2018, 38(1): 26-32.

[Abstract](3180) [FullText HTML] (1343) [PDF 2004KB](30)

Abstract:
In order to actually describe the mechanical behavior of phase transformation and plasticity for NiTi shape memory alloy (SMA), the master equations which based on irreversible thermodynamics theory was derived by assuming two internal variables to characterize phase transformation evolution and plastic evolution. Thus a unified constitutive model was developed by summarizing master equations of phase transformation and plasticity in the loading process of NiTi alloy. Adopting semi-implicit stress integration algorithm to update inelastic strain increment, the phenomenological-based constitutive model was numerically implemented with FORTRAN code. The numerical simulation results were in good agreement with experimental data so that the proposed model validation was conducted. The results show that the proposed model not only can describe well the different deformation stages of NiTi alloy, but also the constitutive behaviors subjected to different strain rates. And it provides the basis for the practical application of NiTi alloy in the condition of impact and high speed cutting.

Stress Field Simulation of Single Crystal Turbine Blade During Unidirectional Solidification

Shifeng LI, Aijie HE, Fei QIU

2018, 38(1): 33-39.

[Abstract](2802) [FullText HTML] (1366) [PDF 4389KB](38)

Abstract:
According to the bottle neck problem about low size precision and large wall thickness deviation of the single crystal turbine blade, considering the inaccuracy factors of boundary conditions during unidirectional solidification process, the contact element method was used to study the interaction between the blade and the shuttering. Meanwhile, the practice temperature field data, the finite element method with the coupled stress field and temperature field, were used to simulate the unidirectional solidification of the single crystal turbine blade. Based on the analysis result, the stress distributing and blade deformation were qualitatively discussed. The result indicates that the max-residual stress presents at the root air-inlets, and the max-residual stress of root air-inlets is 28.4% higher than that of blade-body. The dynamic change of the temperature and the stress can basically been reflected by the coupled temperature/stress method. It can provide references for modifying process for reducing the cast residual stress, improving dimensional accuracy and dimensional stability in the unidirectional solidification process.

Thermodynamic Calculation of Equilibrium Phases of K488 Alloy

Fanguo MENG, Shengguo KONG, Wei LI, Jiantao WU, Juntao LI

2018, 38(1): 40-46.

[Abstract](2814) [FullText HTML] (1373) [PDF 5313KB](21)

Abstract:
The influence of equilibrium and alloy elements on the precipitation phases of K488 alloy was calculated and experimental analyzed by using Thermo-Calc thermodynamic calculation software. The results of calculation and experiment are shown that the alloy equilibrium phases are γ, γ', σ and carbides. In the alloy solidification process, Mo, Ti segregations are more serious. With the increase of C and Nb content, MC precipitation increased, but precipitation temperature decreased, the content of Ti is on the contrary. the increase of Al, Ti contents, γ' phase precipitations amount and precipitation temperature gradually increased. The content of Cr has most influence on the precipitation amount and precipitation temperature of the sigma phase. The calculation and experimental results have good consistency.

Microstructure and Properties of AlSi10Mg Powder for Selective Laser Melting

Pengjun TANG, Xiaolei HE, Bin YANG, Cui SHAO, Xingyuan WANG, Li HUANG, Peiyong LI

2018, 38(1): 47-53.

[Abstract](2855) [FullText HTML] (1328) [PDF 3548KB](46)

Abstract:
The AlSi10Mg powder was prepared by supersonic gas atomization. After classified, the powder was fabricated into block by selective laser melting (SLM). The microstructure, phase, and evolutions of powder and block were investigated by optical microscope, scanning electron microscope and X-Ray Diffraction. The tensile properties of SLM block were tested by tensile experiments at room temperature. The results show that the size distribution of AlSi10Mg powder after classified can meet the requirements of SLM technology. The powder always is spherical and spherical-like. Meanwhile, the microstructure of powders is fine and uniform, which contain α(Al) matrix and (α+Si) eutectic. In addition, the melt pool boundaries of SLM block are legible. The microstructure is also uniform and densified, the relative density approaches to 99.5%. On the other hand, only α(Al) and few Silicon phase are detected in this condition, due to the most alloying elements are dissolved in α(Al) matrix. At room temperature, the ultimate tensile strength of SLM block reaches up to 442 MPa.

Microstructure and Properties of 7A99 Aluminum Alloy Forging after Two-step Aging Treatment

Shaohua WANG, Zhifeng MA, Xianfeng ZHANG, Gang SUN, Zhaohui FENG, Zheng LU

2018, 38(1): 54-59.

[Abstract](2668) [FullText HTML] (998) [PDF 3279KB](27)

Abstract:
Effects of two-step aging treatment on the microstructure and mechanical properties of 7A99 forged aluminum alloy were studied using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test and fracture toughness test. The results show that after 120℃/4 h+165℃/8 h two-step aging treatment, the ultimate tensile strength, yield strength, elongation and electrical conductivity are 548 MPa, 513 MPa, 12.0% and 38.2% IACS, respectively. Meanwhile, the L-T toughness fracture is 30.5 MPa·m^1/2.The fracture mode of the alloy is transgranular dimple fracture mechanism, and the major precipitates are η' and η phases under the aging condition.

Loading Transfer in Structure of Aluminum Alloy Plate Bonded by CFRP

Zhouhui YU, Peizhong ZHAO, Fangyou HU

2018, 38(1): 60-68.

[Abstract](2792) [FullText HTML] (1388) [PDF 5827KB](19)

Abstract:
Tensile tests of aluminum plate repaired with carbon fiber sheet were conducted, the effects of bonding length, layer number and bonding way on load transfer had been discussed, the failure process, failure characteristics, strain distribution and change law were also analyzed, Effects of CFRP reinforced intact specimens and damaged specimens were compared. Test results indicate that adopt double adhesive, the load of damaged specimen can be greatly increased while has no significant effect on intact sample. Increasing layer number can improve the bearing capacity of repaired specimen and reduce the strain gradient at the end and damaged region, also the stress concentration problem is eased. Although the improvement of bearing capacity is limited through increasing the length of carbon fiber sheet, the stress distribution of glue layer has been improved, the strain gradient at the end and damaged region are also reduced, so it is conducive to improve the whole performance of repaired component.

Preparation and Mechanical Properties of Aligned Discontinuous Carbon Fiber Composites

Hua DENG, Junpeng GAO, Jianwen BAO

2018, 38(1): 69-74.

[Abstract](2929) [FullText HTML] (1370) [PDF 3589KB](43)

Abstract:
Aligned discontinuous carbon fiber composites were fabricated from aligned discontinuous carbon fiber prepreg, which was prepared from continuous carbon fiber prepreg via mechanical high-frequency cutting. The internal quality and mechanical properties were characterized and compared with continuous carbon fiber composites. The results show that the internal quality of the aligned discontinuous carbon fiber composites is fine and the mechanical properties have high retention rate after the fibers were cut compared with continuous carbon fiber composites. The minimum retention rate of 0° tension strength is 63%, and the modulus is basically without chang. The minimum retention rates of 0° flexural strength and modulus are 85% and 78% respectively. The mechanical properties of aligned discontinuous carbon fiber composites are much better than that of the random oriented carbon fiber composites.

Densification and Mechanical Properties of ZrN-Nb Composites

Yan ZHANG, Yingkui GUO

2018, 38(1): 75-79.

[Abstract](3128) [FullText HTML] (1332) [PDF 1445KB](23)

Abstract:
Densification of zirconium nitride (ZrN) ceramics was investigated by vacuum hot pressing at temperatures range from 1500℃to 2000℃with Nb as sintering additive. Densification was enhanced with Nb addition. ZrN with 5mol% Nb addition achieved a relative density of 98.5% at 1600℃.XRD and lattice parameter measurements indicated that there were structural differences between samples sintered in different temperatures. It was likely that due to the presence of point defects by changes in stoichiometry, the kinetics of mass transport enhanced. As a result, the relative density of the zirconium nitride (ZrN) ceramics have been improved, thus the fully densed ZrN ceramics can be prepared in a relative low temperature. The density, the room-temperature mechanical properties of ZrN ceramics are increased after the addition of Nb. Zirconium nitride (ZrN)doped with Nb sintered at 1600℃ are measured and obtained elasticity modulus of 238 GPa, flexural strength of 463.3 MPa, fracture toughness of 7.0 MPa·m^1/2 and hardness of 10.7 GPa.

High Temperature Mechanical Constitutive Modeling of a High-Nb TiAl Alloy

Chengli DONG, Huichen YU, Zehui JIAO, Fantao KONG, Yuyong CHEN

2018, 38(1): 80-87.

[Abstract](2815) [FullText HTML] (1323) [PDF 4266KB](24)

Abstract:
Uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep experiments of a novel high-Nb TiAl alloy (i.e. Ti-45Al-8Nb-0.2W-0.2B-0.02Y (atom fraction/%)) were conducted at 750℃ to obtain its tested data and curves. Based on Chaboche visco-plasticity unified constitutive model, Ohno-Wang modified non-linear kinematic hardening was introduced in Chaboche constitutive model to describe the cyclic hardening/softening, and Kachanov damage was coupled in Chaboche constitutive model to characterize the accelerated creep stage. The differential equations of the constitutive model discretized by explicit Euler method were compiled in to ABAQUS/UMAT to simulate the mechanical behavior of high-Nb TiAl alloy at different test conditions. The results show that Chaboche visco-plasticity unified constitutive model considering both Ohno-Wang modified non-linear kinematic hardening and Kachanov damage is able to simulate the uniaxial tensile, low cycle fatigue, fatigue-creep interaction and creep behavior of high-Nb TiAl alloy and has high accuracy.

Atomic Simulation of Fatigue Crack Growth Mechanism of Single Crystal γ-TiAl Alloy

Ling ZHANG, Dechun LUO, Xiangxia BAI, Zhiyuan RUI

2018, 38(1): 88-94.

[Abstract](3409) [FullText HTML] (1389) [PDF 3337KB](32)

Abstract:
In order to study the relationship of fatigue property、crack growth and organization form of TiAl alloy, the micro crack growth and micro deformation mechanism of single crystal γ-TiAl alloy with an embedded boundary crack under cyclic loading were studied by means of molecular dynamics and velocity loading. Results show that the crack growth process and micro deformation mechanism of single crystal γ-TiAl alloy under cyclic loading were divided into three stages. The mechanical properties are affected by the defects of crack tip lattice distortion, prismatic dislocation slip, Lomer-cottrell dislocation group formation, stacking fault start, deformation twin, etc. and their interaction results in the loading process. The mechanism of crack growth and the mechanism of plastic deformation at different stages were quite different. The research results provide a strong theoretical guidance for improving the performance of γ-TiAlalloys under complex external loading conditions.

Low Cycle Fatigue of Single Crystal Nickel-based Superalloy DD6 at 1100℃

Shichao ZHANG, Xudong LI, Huichen YU, Xueqin HOU

2018, 38(1): 95-100.

[Abstract](3138) [FullText HTML] (1389) [PDF 3500KB](41)

Abstract:
The total strain-controlled low cycle fatigue(LCF) behaviors of a single crystal superalloy DD6 at 1100℃ for R=-1 and 0.05 were investigated. The results of LCF tests indicated that the cyclic hardening/softening behavior of the alloy not only has the relationship with the microstructure of the material, but also the loading status. The mean stress relaxation occurred under asymmetric straining. The rate of mean stress relaxation increased with the increasing of strain amplitude; when R=-1, the alloy shows tension-compression asymmetry behavior. All the LCF data obtain under various ratios were well correlated by three models for lifetime prediction, the precision rates predicted are fallen into the factor of±2 times scatter band.

2018 Vol. 38, No. 1