航空材料学报

2015-05-Catalog

2015, 35(5): .

[Abstract](1395) [PDF 2446KB](5)

Abstract:

Compositions Design of GH4169 Alloy Based on Thermodynamic Calculation

Yong-wang LI, Fu-bin LIU, Zhou-hua JIANG, Ke-bin LI, Xin GENG, Xu CHEN

2015, 35(5): 1-6.

[Abstract](2902) [FullText HTML] (1260) [PDF 1955KB](17)

Abstract:
The redistribution law of alloy elements in alloy GH4169 during the process of solidification was predicted. The result shows that Niobium is one of the most serious segregation elements during solidification. The influence of main alloy elements on the mushy zone temperature difference and main equilibrium precipitated phases, especially the strengthening phase γ' as well as δ were analyzed by using the Thermo-Calc software and the corresponding nickel-based database. It is showed that the mushy zone temperature difference is shortened, the precipitation of γ' phase would be promoted, but δ phase is inhibited after adjusting the content of elements appropriately, then the important theory basis for the development of investigating less segregation, stable performance of GH4169 was provided.

Characterization Study of Duplex-hardened 13Cr4Mo4Ni4VA Steel

Zhi-hua JIANG, Chun-zhi LI, Jian-guo ZHANG, Jian-jun JIN, Xiao-jun TONG, Xiao-zhen WANG

2015, 35(5): 7-12.

[Abstract](2855) [FullText HTML] (1266) [PDF 4282KB](8)

Abstract:
Duplex thermochemical processing of 13Cr4Mo4Ni4VA steel was carried out, which involves carburizing (followed by hardening and tempering) and then nitriding. Optical microscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, electron probe micro-analyzer, and microhardness tester were used to study the characterization of the duplex-hardened 13Cr4Mo4Ni4VA steel. Distinct from traditional case hardening process, carbon and nitrogen introduced into the matrix during duplex thermochemical process created duplex case structure with selected solubility gradient of carbon and nitrogen, comprising of nitrided layer and then carburized layer. In nitrided layer, very few intergranular nitrides were found, fine precipitates of Cr₂(C,N), Mo₂C with lamellar microstructure and angstrom-scale flake of Mo₂N formed inside the tempered martensite substrate。Solid solution strengthening by carbon and nitrogen interstitially dissolved and precipitation hardening by fine precipitates caused favorable hardness gradient of superior surface hardness (>70HRC) and deeper hardened layer, and excellent distribution of residual compressive stresses were produced in duplex hardening case.

Tensile Behavior and Deformation Mechanism of Single Crystal Superalloy DD6 at 760℃ and 1070℃

Jian YU, Jia-rong LI, Zhen-xue SHI, Shi-zhong LIU, Mei HAN

2015, 35(5): 13-20.

[Abstract](3139) [FullText HTML] (1344) [PDF 4169KB](36)

Abstract:
The tensile behavior and deformation mechanism of secondary generation single crystal superalloy DD6 at 760℃ and 1070℃ were investigated by mechanical test, TEM and SEM. The results reveal that the γ' phase is cut by dislocation and stacking fault and thermally activated hardening occur at 760℃ tensile deform of DD6 alloy. The stress-strain curves show double stages feature and fracture mechanism show quasi-cleavage. During tensile deformation at 1070℃, the dislocations slip mainly in γ phases matrix channel by overcoming γ' phases. The stress-strain curves exhibit a curved feature and fracture mechanism show dimple model.

Oxidation Resistance of NiCrAlY Coating and Evolution of Microstructures during Oxidation

Xin-ge ZHANG, Chang-guang DENG, Chun-ming DENG, He-zhong PEI

2015, 35(5): 21-26.

[Abstract](3030) [FullText HTML] (1290) [PDF 2374KB](13)

Abstract:
NiCrAlY coatings were prepared on cast Ni-based superalloy K438 using low pressure plasma spraying (LPPS).The oxidation kinetic law of coatings and substrate at 950℃ for 100h was studied. Evolution of microstructure and element distribution of coatings and substrate after oxidation for different hours was analyzed by SEM and EDS. The results show that mass gain of coatings whose oxidation kinetic curve obeyed the parabolic law during oxidation is little, the Al₂O₃ protective scale of about 1.5μm thickness was formed after 100h oxidation. Substrate is oxidized quickly at the beginning, and destructive oxidation is happened after 60h and then mass loss is began quickly. The results of SEM and EDS show that the elements diffused during oxidation slowly, and the diffusion distance is reached 90μm, and the denser coating is lead.

Effect of Vacuum Pre-oxidation Treatment on Oxidation Behavior of Thermal Barrier Coating

Zhong DU, Quan-sheng WANG, Yan-bo LIU, Yun-kai LI

2015, 35(5): 27-31.

[Abstract](3439) [FullText HTML] (1267) [PDF 1762KB](11)

Abstract:
NiCoCrAlY bond coating was prepared by high velocity oxy-fuel(HVOF) spray and top coating was prepared by plasma spray. Pre-oxidation was conducted before the high temperature isothermal oxidation. Effect of vacuum pre-oxidation on the oxidation behavior of thermal barrier coatings was studied by high temperature static oxidation experiment. The results show that a dense and continuous α-Al₂O₃ film is formed after the pre-oxidation treatment. After oxidation for 800h at 1050℃, a TGO, composed of α-Al₂O₃ and a large amout of spinel-type oxides, was formed in as-sprayed coating. On the contrary, a TGO, mainly composed of α-Al₂O₃, is formed in the coating after pre-oxidation treatment. Pre-oxidation treatment can postpone the formation of spinel oxide effectively and then slow down the growth rate of thermally grown oxide(TGO).

High Temperature Oxidation Behavior of Pt Modified Aluminide Coating on Single Crystal Superalloy

Jian-wei DAI, Jun YI, Zhan-kao WANG, Kai WANG, Zhen-hua XU, Li-min HE

2015, 35(5): 32-38.

[Abstract](2873) [FullText HTML] (1278) [PDF 2334KB](22)

Abstract:
Single aluminide and Pt modified aluminide coatings were fabricated by chemical vapor deposition (CVD) on the single crystal superalloy substrates and their high-temperature oxidation behaviors at 1050℃ were investigated. The phase composition and microstructure of the two aluminide coatings were analyzed by XRD, SEM and EDS. The results indicat that both of the oxidation kinetics curves of the two aluminide coatings are in accord with parabolic rule after oxidation at 1050℃ for 250h. The performance of oxidation resistance of Pt-Al coating has been improved more than two folds as compared with single Al coating. The two aluminide coatings are mainly composed of three phases of β, γ' and α-Al₂O₃. The spallation of oxide scale is gradually observed on both of the two coatings' surface with the increment of oxidation time. However the spallation area of Pt-Al coating is relatively smaller than that of Al coating. The phase transition, the penetration of γ' phase and the early formation of mixed oxides are probably the primary reasons responsible for the degradation of the coatings. The addition of Pt element can reduce the velocity of β→γ' phase transition, inhibiting the outward diffusion of refractory metal elements from substrate to coating and further ensuring the formation of high quality α-Al₂O₃ scale.

Effect of Precipitation Strengthening during Natural Aging in Al-Mg-Si Alloy

Mu-chun ZHONG, Feng JIANG, Hong-feng HUANG

2015, 35(5): 39-45.

[Abstract](3574) [FullText HTML] (1273) [PDF 2517KB](18)

Abstract:
In order to investigate the effect of natural aging (for different storage time) and subsequent artificial aging in 200℃/2h on microstructure and property of Al-Mg-Si alloys, TEM, HRTEM, X-Ray analysis and tensile strength, hardness, electrical conductivity measurements were taken. It reveals that natural aging does a favor to alloy strength and hardness for the sake of precipitation influences. Moreover, natural aging(8h) + artificial aging is better than traditional artificial aging, as the former method could groduce smaller size, more separated precipitations. Without natural aging, the α(Al) matrix has sufficient Mg,Si solute atoms, so it could precipitate larger precipitation particles. While during 8h natural aging, some atom clusters precipitate from the α(Al) matrix, which could be the center of precipitation and finally generate more strengthening precipitation β" phase. As a result, the best heat treatment is natural aging(8h) + artificial aging(200℃/2h).

Fracture Performance of Direct Aging GH4169 Superalloy

Xiao-chang XIE, Zhi-gang CHAI, Quan LI, Chun-feng TANG, Zhen-ye ZHAO

2015, 35(5): 46-56.

[Abstract](2874) [FullText HTML] (1353) [PDF 8758KB](21)

Abstract:
The fatigue fracture surface of DAGH4169 superalloy smooth specimen (K_t=1) and notch specimen (K_t=3, 4) after rotating bending fatigue test carried out at room temperature and 650℃ were investigated by Scanning Electron Microscope (SEM). The results indicate that the fatigue fracture surface of DAGH4169 superalloy smooth specimen (K_t=1) at room temperature has multiple crack initiation feature under high fatigue load, while single crack initiation feature under low fatigue load. And the fatigue cracks initiate at the machining defects of the surface. Multiple cracks initiated at the machining defects of the notch foot under different level fatigue load is observed for the DAGH4169 superalloy notch specimen (K_t=3, 4) at room temperature. Single crack initiated at machining defects of the surface is observed from the fatigue fracture surface of DAGH4169 superalloy smooth specimen (K_t=1) at 650℃. And DAGH4169 superalloy notch specimen (K_t=3, 4) shows multiple crack initiation feature, the fatigue cracks initiate at the machining defects of the notch foot. For all the observed specimens, as fatigue load decreases, crack initiation region becomes smooth, the area of fatigue failure region becomes smaller, the distance between fatigue failure region and centre of fracture is bigger.

Galvanic Corrosion of TB5 Titanium Alloy of Anodic Oxidation Film

Yong-jin YANG, Xiao-yun ZHANG, Ming-hui LIU

2015, 35(5): 57-62.

[Abstract](3088) [FullText HTML] (1295) [PDF 1687KB](12)

Abstract:
Anti-galvanic corrosion anodic film was prepared on the surface of TB5 titanium alloy by means of pulse anodizing technology. The morphology, microstructure and chemical composition of the anodic film were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The galvanic corrosion properties of TB5 titanium alloy-aluminum alloys coupling and TB5 titanium alloy-steels coupling were measured. Anti-galvanic corrosion mechanism of the anodic film on titanium alloy surface was also investigated using electrochemical methods. The results showed that the anodic film was composed of anatase TiO₂ and undefined TiO₂. The film was not compact and porous, with a thickness of around 2-3μm. Electrochemical analysis indicated that the reaction resistance of titanium alloy increased after anodizing, leading to decrease of galvanic corrosion current density. Therefore, the galvanic corrosion susceptibility of titanium alloy can be effectively reduced by pulse anodizing treatment.

Flow Field of Double Layer Atomizer

Yang LIU, Zhou LI, Guo-qing ZHANG, Wen-yong XU, Hua YUAN, Na LIU, Liang ZHENG, J MI

2015, 35(5): 63-69.

[Abstract](2886) [FullText HTML] (1310) [PDF 5395KB](19)

Abstract:
Using a computational fluid dynamics(CFD) software, the gas flow field and atomization process of an low pressure double layer atomizer were investigated to discuss the effect of primary atomizer on gas recirculation zone and liquid metal atomization. Results show that primary atomizer can restrain adverse effect of the recirculation zone, which is beneficial to liquid metal flow. Considering that increasing primary atomizer pressure could raise gas mass flow rate, 0.15MPa/0.68MPa-0.2MPa/0.68MPa conditions are beneficial. The liquid atomization process of this double layer atomizer contains membrane disintegration process which is similar to close-coupled atomizer, and the droplets distributions relate to their diameters.

Mechanical Properties and Fracture Characteristics of Welded Joint in GH536 Ni-based Superalloy

Zhen-wei WEI, Chang-kui LIU, Yu-li GU, Chun-hu TAO

2015, 35(5): 70-74.

[Abstract](3363) [FullText HTML] (1285) [PDF 2441KB](11)

Abstract:
Microhardness, tensile properties and fracture toughness of based metal and different zones in welded joint for GH536 obtained by gas tungsten arc welding(GTAW) were studied. The results show that hardness in HAZ is equal to BM, however, hardness becomes higher from fusion line to weld center for finer dendritic structures. The tensile strength σ_b、yield strength σ_s and elongation δ at room temperature(RT) are 810MPa,392MPa and 30%, which reach 99.6%,99.7% and 93.8% of based materials',respectively;The σ_b,σ_s and δ at 500℃ are 678MPa,300MPa and 26%, which reach 98.1%,96.8% and 78.8% of based materials',respectively;The welded joint of GH536 has good mechanical properties. Fusion zone is the weak link of welded joint for higher microstructure heterogeneity.Based metal and welded joint break mainly in the way of plastic rupture both at RT and 500℃.

Forming Quality of Composite Hat-stiffened Structure by Autoclave Co-curing Process

Yuan-qi ZHOU, Yong-wei PU, Li-hua ZHAN, Yang SONG, Shu-jian LI, Wen-fei PENG

2015, 35(5): 75-81.

[Abstract](3420) [FullText HTML] (1228) [PDF 4239KB](15)

Abstract:
Composite hat-stiffened structures were fabricated using different mandrels under the co-curing process. Based on the ultrasonic phased array nondestructive testing technology, the inspection and analysis of forming quality at different positions of the hat-stiffened structure were carried out. The geometrical shape of the hat-stiffened structure located in the crown was characterized using phased array B-scan; the forming precision of web was measured by the gate location technology; and the specific quantitative relationship between the interface bonding quality of the flange with the skins and ultrasonic coefficient was found. Meanwhile, combined with microscopic metallographic analysis, the ultrasonic phased array testing result is verified from the view of microcosmic, and the optimal mandrel structure with φ 12mm was ultimately confirmed under certain co-curing process.

Performance Comparison of Four Anti-bird Strike Aircraft Skin Material

Yong-qiang LIU, Xiang-ying WANG, Chang-hong TANG, Zhen-zhou FENG, Chao-guang HUANG

2015, 35(5): 82-89.

[Abstract](2865) [FullText HTML] (1390) [PDF 2923KB](30)

Abstract:
Taking IL-76 aircraft wing leading edge structure as the object, the comparison research of the bird impact resistant properties of the aluminum alloy, GLEAR layer board, metal honeycomb sandwich panel structure and composite honeycomb sandwich panel structurewas undertaken. Using large nonlinear dynamics software PAM-crash, the structure finite element model was established. The correctness of the analysis method was verified through the numerical simulation calculation and the experiment. From the analysis of structural failure and energy absorption characteristics, it is found that under the same conditions, the GLEAR laminate skin has the lightest weight, strongest bird impact resistance, highest energy absorption efficiency and best properties.

Research Status of Lamellar Orientation and Lamellar Spacing Control of Full Lamellar TiAl Alloy

Xiao-peng LI, Bing-gang ZHANG

2015, 35(5): 90-98.

[Abstract](3264) [FullText HTML] (1250) [PDF 3048KB](18)

Abstract:
Lamellar orientation and lamellar spacing have important influence on the mechanical properties of the full lamellar TiAl alloy. In this paper, the relationship between mechanical properties and microstructures of full lamellar TiAl alloy has been systemically reviewed from the aspect of the controlling of lamellar orientation and lamellar spacing. The analysis shows that fine lamellar with single orientation can lead to the best mechanical performance. Alloying, large growth speed and environmental pressure is benefit for fine lamellar, and alloying is the simplest method. Self-seeding technique is one the most promising method to control the lamellar orientation in the future.

2015 Vol. 35, No. 5