航空材料学报

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2021, (2): .

[Abstract](537) [FullText HTML] (256)

Abstract:

Development status and typical application of selective laser melting technology applications in aerospace field

Jiaoxi YANG, Wenliang WU, Changliang WANG, Chenguang LIU, Shuzhi WANG, Daijun YANG, Zheng ZHOU, Hongchao XU

2021, 41(2): 1-15.

[Abstract](1354) [FullText HTML] (567) [PDF 6171KB](163)

Abstract:
Additive manufacturing technology (AM) is a new type of manufacturing technology based on the discrete-stacking principle and processing component with computer model data. Selective laser melting (SLM) is an important technology in the field of additive manufacturing. With its integrated manufacturing characteristics and significant advantages in the field of complex structural parts manufacturing, it has become a key development technology and frontier direction in the field of aerospace manufacturing. This article reviews the material system and application fields of SLM technology, and mainly analyzes the latest process research of SLM technology and typical applications in the aerospace field. It focuses on the research progress and results of SLM iron-based alloys, nickel-based alloys, titanium alloys and aluminum alloys. While SLM technology is widely used in various fields, there are also many problems and shortcomings, such as many internal defects of forming materials, cracks and deformations of high-performance materials, lack of standard systems, and low compatibility of powder materials. Constraints require further in-depth work in these areas.

Uncoupled ductile fracture criterion and its application in aeronautical metallic materials

Hongyue MA, Namin XIAO, Peng QIAN, Shuai LUO, Haiming ZHANG

2021, 41(2): 16-31.

[Abstract](931) [FullText HTML] (257) [PDF 1158KB](59)

Abstract:
Structural lightweight is an important development trend in aerospace and automotive fields, and the demand for lightweight metal materials represented by aluminum alloy, magnesium alloy, and titanium alloy is increasing continuously. Predicting the damage and fracture behavior of advanced metal materials is the key to forming process design and service performance evaluation of high - performance aerospace components, and the development of advanced ductile fracture criteria (DFCs) is the main approach. This paper firstly introduces the microscopic mechanism of ductile fracture of metals, including the shear fracture dominated by shear or compression stress, the tensile fracture dominated by tensile stress, and the mixed fracture. Then, the development history, characteristics, and applications of the traditional uncoupled DFCs are reviewed, and several typical uncoupled ductile fracture models established in recent years as well as their main characteristics and advantages are emphatically discussed. The traditional uncoupled DFCs usually only consider the influence of maximum principal stress or average stress on damage/fracture, and ignore the effect of deviatoric stress, it is not suitable for the prediction of fracture behavior of materials under small stress triaxiality or complex stress state. The recently developed DFCs are more suitable for complex strain path and stress state by considering the joint influence of both stress triaxiality and Lode angle parameter on damage evolution. Whereafter, the development status and typical applications of uncoupled DFCs in aeronautic metals such as aluminum alloy, magnesium alloy, and titanium alloy are reviewed. Finally, this work ends with prospecting the development trend and research direction of DFCs. According to the deformation characteristics of advanced structural metals, new uncoupled DFCs should comprehensively consider the effects of stress state, strain rate, temperature and anisotropy on damage fracture, so as to make it have better applicability and prediction accuracy.

Research progress in the application of optical emission spectroscopy in metal microarc oxidation surface treatment

Yizhao LIAO, Wenbin XUE, Xumin WAN, Yifan ZHANG, Minghao ZHU, Chi XU, Jiancheng DU

2021, 41(2): 32-44.

[Abstract](726) [FullText HTML] (354) [PDF 1447KB](21)

Abstract:
Spark discharge phenomenon in solution is a typical characteristic in metal microarc oxidation (MAO) surface treatment, and the optical emission spectroscopy (OES) is an effective way of characterizing micro-discharge optical emission spectra and studying the MAO mechanism. In this paper, the research status of OES analyses in MAO process of Al, Mg, Ti and their alloys was reviewed, the calculation principle of electron temperature and density in microarc plasma discharge channels was introduced, and the influence of the plasma discharge behavior on the microstructure of MAO coatings at different metals, electrical parameters and electrolyte solutions was evaluated. Furthermore, the different discharge models on the basis of OES analyses were also discussed. The plasma temperature in microarc discharge zone for different metals calculated from OES was in the range of 3000 - 10000 K, which provided the evidence for the growth mechanism of ceramic coatings enhanced by quick molten-solidification process in discharge channel.

Process control and mechanical properties of graphene/Al composites based on flaky powder metallurgy

Boyu JU, Yiwei SONG, Boyang ZHAO, Yijun JIANG, Wenshu YANG, Gaohui WU

2021, 41(2): 45-52.

[Abstract](798) [FullText HTML] (273) [PDF 1998KB](39)

Abstract:
Graphene/Al composites have the characteristics of high strengthening efficiency, synergistic improvement of strong plasticity, and excellent comprehensive performance, which is expected to break through the bottleneck problem of poor strength- plasticity matching of metal matrix composites. However, the dispersion of graphene is an important issue that plagues the preparation of materials. The flaky powder metallurgy technology based on the mechanical ball-milling process can transform the spherical aluminum powder into flakes and realize the uniform dispersion of graphene. In this study, the mechanical ball-milling process was controlled by adding a process control agent (polydimethylsiloxane, PDMS) to prepare flaky Al powder, combined with pressure infiltration technology to prepare 0.6%(mass fraction) GNPs/6061Al composites. The results show that the diameter of flaky aluminum powder increases first and then stabilizes with the prolongation of milling time. As the viscosity of process control agent increases, the diameter of flaky aluminum powder is increased, and the flaky effect of aluminum powder is more obvious. At the same time, the viscosity of graphene defect content decreases first and then increases. Moreover, it is revealed that the graphene defects show a decreasing and increasing change pattern as the viscosity increased. Combined with the structure characterization and mechanical property test, the relationship between properties and structure is discussed, which has provided a reference for the subsequent preparation of graphene/Al composites.

Effect of cooling rate on modification of eutectic silicon during DC semi-continuous casting of 4032 aluminum alloy billet

Yongfu WU, Baocun ZHANG, Ning WANG, Kangcai YU, Guanglei ZHU

2021, 41(2): 53-60.

[Abstract](683) [FullText HTML] (282) [PDF 1234KB](20)

Abstract:
In this work, numerical simulation was used to investigate the distribution of cooling rate during DC semi-continuous casting of 4032 aluminum alloy billets with the diameters of ϕ120 mm, ϕ300 mm and ϕ500 mm. Further, the effect of cooling rate on the modification of eutectic silicon by Sr addition was investigated. The simulation results indicate that the cooling rate from the surface to the center of the billet generally decreases. As the billet diameter increases, the sump depth becomes deeper, the distance between the isothermal lines of liquidus and solidus becomes larger, and the cooling rate at the billet center decreases sharply. The cooling rate affects the modification results of eutectic silicon by Sr addition. When the cooling rate is higher than 1.8 K/s, Sr addition can achieve excellent modification results. However, as the cooling rate decreases, the modification of eutectic silicon becomes worse, even the Sr contents are the same. At the industrial casting conditions, the cooling rates of inner part of the ϕ500 mm billet are below 1 K/s. At this low cooling rate, the Sr content of 0.033%-0.036% is not enough to modify the eutectic silicon any more. To the billet with the diameter as large as 500 mm, the casting speed is the most important factor that influence the cooling rate distribution. But the influenced area is only limited within the distance of R/2 to the surface, and little influence to the center of the billet.

Optimization of high Nb-TiAl alloy impeller investment casting based on ProCAST software

Jinhu LIU, Zhijun JI, Feng LI, Xin FENG, Wen YU, Xianfei DING, Hai NAN

2021, 41(2): 61-71.

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Abstract:
The casting simulation software ProCAST was used to achieve the simulation of the filling and solidification process of the high Nb-TiAl alloy impeller investment casting. The influence of the casting and filling process on the filling and solidification characteristics of alloy melt filling, shrinkage cavity and porosity was studied, and the corresponding process was optimized. The casting test and the non-destructive testing analysis of the casting were carried out, and the anatomical analysis of the casting was performed to verify the distribution of the shrinkage cavity and porosity. The mechanical properties of the impeller at room temperature and high temperature were studied using attached test rods. The results show that ProCAST software is more accurate in predicting shrinkage cavity and porosity of the high Nb-TiAl casting, and the process scheme is optimized by simulation and prediction results to avoid the formation of large shrinkage cavity and porosity in casting, only micro shrinkage cavity less than 22 μm is existed in the final casting. All castings are fully filled, with the tensile strength about 580 MPa at room temperature and about 450 MPa at high temperature of 850 ℃.

Effect of the anodization on high tempreture oxidation behavior and mechanical properties of TiAl alloy

Yating BAO, Yanan WANG, Lei ZHENG, Xiangjun LIN, Guangya HOU, Yiping TANG, Liankui WU

2021, 41(2): 72-81.

[Abstract](561) [FullText HTML] (211) [PDF 1306KB](19)

Abstract:
TiAl alloy was electrochemically anodized in ethylene glycol electrolyte containing with NH₄F to prepare anodic film. The influence of anodization treatment on the oxidation behavior and mechanical properties of the anodized TiAl alloy were then characterized. Results shown that based on the halogen effect a continuous and dense Al₂O₃ oxide scale will generate on the anodized TiAl alloy after high temperature oxidation. After oxidation at 1000 ℃ for 100 h, the weight gain of the anodized TiAl alloy was dramatically decreased from 85.86 mg/cm² to 0.67 mg/cm². Moreover, it is shown that the surface hardness and elastic modulus of the anodized TiAl alloy decreased first and then increased with the prolonging of oxidation time. Meanwhile, the friction coefficient of the anodized TiAl alloy increased comparing to the bare TiAl alloy. The surface wear resistance of the anodized TiAl alloy exhibited similar phenomena. This is because that during high temperature oxidation process, aluminum fluorides selectively transport to the surface through pores or micro-cracks, and are oxidized to Al₂O₃ at the surface region. The influence of anodization treatment on the mechanical properties of the anodized TiAl alloy is attributed to the Al₂O₃ content contained in the oxide scale.

Performance of SiC whisker reinforced SiC_f/SiC composites fabricated by PIP

Zhuoyu JIANG, Xiaoxu LYU, Yiran ZHOU, Zhe QI, Ye GAO, Wenqing ZHAO, Jian JIAO

2021, 41(2): 82-88.

[Abstract](1229) [FullText HTML] (464) [PDF 1214KB](61)

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SiC_f/SiC composites with the polycarbosilane and silicon carbide fiber of different pyrolytic carbon (PyC) interphase thicknesses as the reinforcement phase were fabricated by a polymer impregnation and pyrolysis (PIP) method. And SiC whisker was introduced into the SiC_f/SiC composites to further improve its performance. It is found that the mechanical properties of SiC_f/SiC composites have outstanding tensile strength, fracture toughness and flexural strength of 192.3 MPa, 446.9 MPa and 11.4 MPa·m^1/2,, when the PyC interphase thickness is about 230 nm. After the introduction of SiC whisker, into the SiC_f/SiC composite matrix, the toughening mechanisms such as whisker pull-out, whisker bridging and crack deflection increase the energy consumption when the crack is transferred in the matrix, and the fracture toughness and bending strength of the composite are increased by 22.9% and 9.1% respectively.

Synthesis of Gd₂SiO₅ nano-powders by cocurrent chemical co-precipitation method

Rong LIU, Yalei WANG, Nannan WU, Huaifei LIU, Rutie LIU, Huicong CHENG

2021, 41(2): 89-97.

[Abstract](670) [FullText HTML] (241) [PDF 1400KB](15)

Abstract:
In this paper, nano-sized Gd₂SiO₅ powder was synthesized by a cocurrent chemical co-precipitation method with Gd₂O₃ and TEOS as raw materials. The thermal behavior of precursor, phase composition and microstructure of the obtained powder were investigated, the synthesis mechanism was also discussed. The results show that lower Gd: Si molar ratio in precursor and higher pH value in reaction system can lead to the formation of Gd_9.33(SiO₄)₆O₂ phase. On the contrary, Gd₂O₃ impurity is formed in the obtained Gd₂SiO₅ powder. In this study, the relatively pure Gd₂SiO₅ powder can be synthesized at 1000-1300 ℃ with Gd/Si molar ratio as 20: 11 and pH value in the range of 9-10. The obtained powder inhibits irregular morphology with average grain size of 100-200 nm. During the synthesis process, the precursor is generated in the form of —[Si—O—Gd]— network, and then translated to Gd₂SiO₅ grains, as well as Gd_9.33(SiO₄)₆O₂ and Gd₂O₃ impurities.

Rheological behavior of rosin-sourced anhydride bio-epoxy resin system

Xufeng ZHANG, Dihui LI, Xi QI, Jifeng TONG, Xiaosu YI

2021, 41(2): 98-104.

[Abstract](860) [FullText HTML] (298) [PDF 964KB](28)

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Viscosity is the main rheology parameter of thermosetting resin matrix processing, which is an important factor effecting processing performance. The viscosity-temperature curves at dynamic states and viscosity-time curves at stead state were measured by cone-plate rotate viscosimeter, and the rheology property of bio-based resin system based on rosin-sourced anhydride curing agent was studied according to the optimization improved six parameter dual-arrhenius equation. Two kinds of rheology models were established by fitting reaction rate constant K and pre-exponential factor A according to the exponential or logarithm viscosity relative equation, respectively. The rheology model based on logarithm viscosity relative equation simulation was in good agreement with experimental data than exponential viscosity relative equation fitting. The rheology model demonstrated the law of viscosity change at different processing conditions, which provided necessary scientific basis for processing parameter optimization.

2021 Vol. 41, No. 2