航空材料学报

Microstructure Analysis of Homogenized B93 Aluminum Alloy for Aviation

JIANG Feng, WEI Li-li, JIAN Hai-gen, ZHENG Xiu-yuan, HUANG Hong-feng, WEN Kang

2010, 30(2): 1-6.

[Abstract](1825) [PDF 669KB](481)

Abstract:
The as-cast microstructure of high-strength B93 aluminum alloy used in airplane structure and the evolvement of the microstructure during homogenization have been studied by optical microscopy (OM),X-ray diffraction (XRD) and scanning electron microscopy (SEM). Combined with the DSC curve of different conditions,the slender and narrow non-equilibrium phase enriched zones were found to re-dissolution first during the homogenization.When the homogenization temperature is below 350℃,the supersaturated solid solution decomposes,equilibrium phaseη(MgZn2) precipitates and a spot of non-equilibrium low melting point eutectic phases in grain boundary dissolve. When the temperature is above 460℃,most of the intermetallic compound such as the η(MgZn2) phase,T(AlZnMgCu) phase dissolve back into the matrix,the dendritic network become sparse and the grain boundary become thinner. The Cu element segregates seriously in the ingot. With the homogenization temperature increasing,the continuous reticulation Cu grain boundary phase Al6(CuFe) dissolves and breaks. However,these phases do not dissolve completely. The optimum homogenization process of B93 aluminum alloy is 460℃ for 24h.

Carbide in Spray Formed Superalloy GH742y

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

2010, 30(2): 7-10.

[Abstract](1764) [PDF 985KB](243)

Abstract:
The amount,composition,type,morphology,distribution and stability of MC carbide for spray formed superalloy GH742y were investigated. The result shows that carbide in GH742y enriches with Nb and Tiand M(C,N)forms after Ninstead of Cpartially. Polygonal granular carbonitride present at the grain boundaries and in grains,most of them are sub-micrometer. Carbonitride has good thermal-stability and hardly changes in its amount,size and morphology after 1250℃ solution treatment. It inhibits the movement of grain boundary and grain growth by pinning the grain boundary.

Prediction of Plastic Flow Instability of TA15 Titanium Alloy with Full Lamellar Based on Prasad Criterion

DONG Xian-juan, LU Shi-qiang, WANG Ke-lu, ZHENG Hai-zhong, XIAO Xuan

2010, 30(2): 11-16.

[Abstract](1814) [PDF 890KB](218)

Abstract:
Isothermal constant strain rate compression tests of TA15 alloy with full lamellar have been carried out.The plastic flow instability was predicted in the temperature range 750~1100℃ and strain rate range 0.001~10s-1.The corresponding macro and microstructures of deformed specimens were observed.The results show that the instability criterion predicts a large region of flow instability,which extends to low strain rate region with decreasing deformation temperature. The specimens deformed in (α+β) phase field demonstrates three kinds of flow instabilities,namely macro shear cracks,prior β boundary cracks and flow localization. The flow instability in β phase field is characterized by the elongated prior β grains perpendicular to compression axial and deformation bands distributed in prior β boundaries.

Study on Critical Strains of Dynamic Recrystallization during β Process in TA15 Titanium Alloy using Working Hardening Rate

OUYANG De-lai, LU Shi-qiang, CUI Xia, DONG Xian-juan, WU Cao, QIU Wei

2010, 30(2): 17-23.

[Abstract](1963) [PDF 2310KB](713)

Abstract:
Work hardening rate curve under the large strain and inflection point criterion of dynamic recrystallization from the curve for determining critical strain theory was analyzed based on dislocation. The dynamic recrystallization critical conditions for onset of DRX during β process were established according to the work hardening rate approach,using experimental data obtained during compression deformation in the range of deformation temperature 1050～1100℃ and strain rate 0.001~1s-1.Furthermore,the predicting model of critical strain was determined by the Zener-Hollomon parameter approach. The results indicate that two type of stress-strain curve is observed under present deformation conditions.The critical conditions leads to the appearance of an inflection point in the θ-σ curve and to a minimum value of -∂θ/∂σ when the critical state is attained. There are linear relation between critical strain and peak strain,i.e. εc/εp=0.62.The predicting model of critical strain were established by the function of εc=1.7210-2Z0.0605

Investigation on Thermodynamics Properties of Hydrogen Absorption in Porous TC4 Titanium Alloy

GUO Qing-miao, ZHANG Fang-fang, HOU Hong-liang, REN Xue-ping

2010, 30(2): 24-29.

[Abstract](1829) [PDF 666KB](251)

Abstract:
The thermodynamics properties of hydrogen absorption in porous TC4 titanium alloy was investigated by means of pressure-composition (P-C) isotherm measurements from 673 K to 973 K using a tube-hydrogen treatment furnace. The plateau pressures of the hydrogen absorption at different temperatures in porous TC4 alloy was determined and then the thermodynamic parameters were calculated according to Van’t Hoff equation. Meanwhile,the microstructure evolution before and after hydrogen absorption were observed by scanning electron microscopy (SEM). It was found that there were two pressure plateaus in the pressure-composition (P-C) isotherms,which were induced by αH+βH→βH and βH→βH+δ phase transformations,respectively,and the plateau pressure gradually increased with the hydrogenation temperature increasing. The calculated enthalpy ΔHand entropy ΔS for the βH→δ phase transformation are (-47.07±0.14)kJ·mol-1 and (-125.24±0.17)J·K-1·mol-1,respectively,which indicated that the hydrides in porous TC4 alloy was less stable than those in Ti-H and density TC4 alloys. When hydrogenation was carried out at 673K,some cracks were observed after hydrogenation,which was related to the volume change induced by hydride formation with high hydrogen content. When hydrogenation temperature increased up to 973K,a plate-like morphology with various was found.

Microstructure and Properties Study of 32Cr3MoVE Deep Nitrided Steel

JIANG Zhi-hua, LI Zhi-ming, TONG Xiao-jun, LIZhi

2010, 30(2): 30-34.

[Abstract](1821) [PDF 723KB](585)

Abstract:
The microstructure and property of 32Cr3MoVE deep nitrided steel were characterized and analyzed. The contact fatigue experimental study was carried out for 32Cr3MoVE deep nitrided steel and for presenting a striking contrast,we also carried out aimultaneously the same contact fatigue experiment for the 18CrNi4A carburized steel and 32Cr3MoVE conventional nitrided steel. The failure morphology analysis for 32Cr3MoVE deep nitrided steel showed that two modes of fatigue crack formation worked,but the fatigue failure was mainly due to the formation and expansion of subsurface cracks. 32Cr3MoVE deep nitrided steels long-life Mechanism was explored as follows:deep nitriding process leads to a case depth between 0.6mm and 0.8mm,ahigh surface hardness,superior case microstructure,favorable hardness gradient and excellent distribution of residual compressive stresses.

Effect of Friction Stir Processing on Dynamic Deformation Behavior of Mg-2.67%Nd-0.5%Zn-0.5%Zr Alloy

SHA Gui-ying, YU Tao, SUN Xiao-guang, WANG Hong-shun

2010, 30(2): 35-39.

[Abstract](1772) [PDF 685KB](205)

Abstract:
Mg-2.67%Nd-0.5%Zn-0.5%Zr alloy was treated with FSP technology with different parameters. The impact experiments for the alloy and FSP treated alloy were carried out using the Hopkinson Pressure Bar. The effects of FSP on the dynamic stress-strain behavior and its strain rate effects were analyzed. Results show the microstructure of the alloy after FSP treatment is refinement obviously because of dynamic recrystallization generate in the alloy,and the average grain size of this alloy from 60μm reduced to below 10μm. The dynamic stress-strain behavior of Mg-2.67%Nd-0.5%Zn-0.5%Zr alloy shows remarkable rate strengthening effect with strain rate increasing,but which of the alloy after FSP treatment is insensitive to strain rate under high-speed impact loading. This mainly results from obvious increasing of the deformation resistance for the alloy,which is induced because strengthening of grains refinement and small,dispersive precipitates in the alloy after FSP treatment.

Evolution of Microstructure and Properties of Surface Layer after Shot Peening of TC21 Titanium Alloy

SONG Ying-gang, GAO Yu-kui, LU Feng, ZHAO Zhen-ye

2010, 30(2): 40-44.

[Abstract](1889) [PDF 669KB](392)

Abstract:
The surface layer of shot peened TC21 titanium alloy was conducted by TEM,X-ray and Nano-indentation. The results indicate that an elastic-plastic strength layer is formed on the surface of TC21 alloy after shot peening. During the deformation processing,the activated slip system in a and c plane increase the density of the dislocations,and formed the net in α phase. After the shot peening,the hardness of the nanoindentaion is 6.7GPa and increased two times. The residual stress in the strength layer decreases from surface to inner and the thickness of the surface layer is about 370μm.

Effect of AlTiN Composition Multilayer Coatings Periodic Structure on Adhesion

LUO Qing-hong, YANG Hui-sheng, LU Yong-hao, LOU Yan-zhi, YU Dong-li, WANG Yan-bin

2010, 30(2): 45-50.

[Abstract](1782) [PDF 1049KB](317)

Abstract:
The AlTiN composition multilayer coatings were deposited on high speed steel substrates with a medium-frequency (MF) reactive magnetron sputtering system using rectangular TiAl targets. During deposition of AlTiN multilayer thin films nitrogen flux was alternated in different periods. X-ray diffraction (XRD),Field emission scanning electron microscopy (FE-SEM),and high-resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure of AlTiN composition multilayer coatings. Their mechanical behaviors and adhesion properties were investigated using nano-indenter and scratch test. The result indicates that the presently deposited multilayer thin films consisted of alternating AlTiN with different nitrogen contents in different layer thicknesses. In each layer,AlTiN exhibits nanocomposites of nanocrystallites embedded into amorphous matrices despite of their nitrogen content. The difference between bilayer is that AlTiN layer with lower nitrogen content has a lower density of nanocrystallites. Formation of multilayer structure greatly increases the critical load at which film-substrate interface delamination occurs and adhesion energy although it only slightly increases both hardness and elastic modulus values,which indicates that formation of multilayer structure is beneficial for improvement of adhesion. Increase of nitrogen flux enhances this effect.

Twin Model on Dark Features Formation in Diamond Films by Deposition Temperature Changed

JIANG Chun-sheng, LIU Zheng, GUO Shi-bin, TANG Wei-zhong

2010, 30(2): 51-57.

[Abstract](1766) [PDF 1428KB](249)

Abstract:
Dark feature is important foreach performance of polycrystal diamond film. Twin mechanism on dark feature was established. The simulation basic assumption that penetration twin were formed on diamond face with deposition temperature changed and were grown with initial grains as α2d.Dark features were formed at grain boundary which it was formed such as "canyon" shape and the angle between adjacent crystal face was too small because it was difficult for gas diffusion. Twin model was simulated by Level-Set method and was confirmed by experiment. The result indicates the number of dark feature is accelerated by increased grain boundary due to formed of twins with deposition temperature changes.

Interdiffusion Barrier Ability of CrN Interlayer at High Temperature

LI Wei-zhou, LIU Shan-chuan, GONG Jun, SUN Chao, JIANG Xin

2010, 30(2): 58-63.

[Abstract](1938) [PDF 1283KB](235)

Abstract:
In order to suppress the element interdiffusion,the CrN interlayer was introduced as a diffusion barrier into the NiCrAlY/DSM11 interface by arc ion plating (AIP) technique. The morphologies of the as-deposited CrN,the annealed and thermally exposed NiCrAlY/DSM11 and NiCrAlY/CrN/DSM11 were observed by scanning electron microscope (SEM). With the aid of energy-dispersive spectra (EDS),the element distribution was studied along the cross-section of the specimens. The phase structures of the overlayer and diffusion barrier were analyzed by X-ray diffraction (XRD). The morphologies of the diffusion barriers were observed by transmission electron microscope (TEM) in the annealed and exposed NiCrAlY/CrN/DSM11. The oxidation-resistance of the single NiCrAlY coating and NiCrAlY/CrN duplex coating was investigated after thermal exposure at 1100℃ in air and the ability was evaluated of the CrN diffusion barrier to suppress element interdiffusion at high temperature. The results show that the NiCrAlY/CrN coating system provides more effective protection for the substrate than the single NiCrAlY coating and the diffusion barrier effectively decreases the element interdiffusion,which is attributed to the chemical reaction of CrN→Cr2N→TiN in the diffusion barrier during vacuum annealing and thermal exposure.

Study on Properties of Ni-Fe-Pr-P Alloy Fabricated by Electroless Method on Surface of Glass Fiber

WU Dao-wei, HUANG Ying, SU Wu, LI Yu-qing

2010, 30(2): 64-67.

[Abstract](1765) [PDF 1302KB](378)

Abstract:
For getting coatings with better properties,the Ni-Fe-Pr-P alloy was deposited on the surface of glass fiber via electroless plating process.The Ni-Fe-Pr-P alloy was even and compact. The morphologies of the coatings were observed through the scanning electron microscope (SEM). The elements and their content were analyzed through energy dispersion spectroscopy analysis (EDS). The electric and magnetic properties were studied via the digital multimete and the vibrating sample magnetometer. The absorption properties were measured using a vector network analyzer in frequency rang of 8.2～12.4GHz. The experiment results show that there is almost no magnetic loss of the coatings doped praseodymium,but the conductivity of the coatings is extremely large and the praseodymium content is 9.21% at most. The plating is a typical dielectric loss material. Meanwhile,the proper praseodymium can reinforce the absorption properties.

Characterization and Preparation of C-AlPO₄ High Temperature Oxidation Resistant Coatings by Hydrothermal Electrophoretic Deposition

YANG Wen-dong, HUANG Jian-feng, CAO Li-yun, XIA Chang-kui

2010, 30(2): 68-72.

[Abstract](1781) [PDF 514KB](263)

Abstract:
Cristobalite aluminum phosphate(C-AlPO4) high temperature oxidation resistant coatings were deposited on C/C-SiC composites surface by hydrothermal electrophoretic deposition process. Phase compositions and microstructures of the as-prepared multi-coatings were characterized by XRD and SEM. The charge mechanisms of C-AlPO4 powder in dispersion medium and the stability of disperse of C-AlPO4 suspension were studied. Optimize condition was got by orthogonal experiments. Phase compositions,microstructures and oxidation resistance of the as-prepared coatings under optimize condition were investigated. Results show that C-AlPO4 molecules have positive charges because of absorbing H+ broken by organic medium molecule. The stability of C-AlPO4 suspension is best in the isopropyl alcohol. The optimization technological conditions for preparing the C-AlPO4 coating are the deposition voltage 220V,deposition time 25min and the deposition temperature 100℃; the coatings prepared at optimization technological conditions effectively protect C/C composites from oxidation at 1500℃ in air for 37h with a weight loss of 0.53%.

Effect of Thermal Treatment Temperature on Phase Composition and Microstructure of Nano-Yttrium Silicate Powders

CAO Li-yun, XU Bin-sheng, HUANG Jian-feng, WANG Ling-ling, XIA Chang-kui

2010, 30(2): 73-76.

[Abstract](1742) [PDF 520KB](295)

Abstract:
Yttrium silicates nanocrystallites were prepared by a microwave-hydrotherma1 method using Y(NO3)3·6H2O,Na2SiO3·9H2O and NaOH as main source materials. The influence of thermal treatment temperature on the phase composition and microstructure of yttrium silicates crystallites was investigated.The yttrium silicates powders were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM)and transmission electron microscopy(TEM).Results show that yttrium silicates nanocrystallites have been successfully prepared by the microwave-hydrothermal method,but their crystallization property is poor. Y2SiO5content of the yttrium silicates nanocrystallites increases and the grain changes from cotton fiber pattern to columnar pattern with the increase of thermal treatment temperature. The increase of thermal treatment temperature is also benefit for the growth of yttrium silicates crystallite,and the growth of Y2SiO5 nanocrystallites is along [378].

Phase Transition and Depolarization Properties of BiFeO₃ Doped K_0.5Na_0.5NbO₃-LiSbO₃ Lead-free Piezoelectric Ceramics

JIANG Min-hong, LIU Xin-yu, GONG Xiao-bin, CHENG Jun

2010, 30(2): 77-81.

[Abstract](1906) [PDF 1171KB](411)

Abstract:
BiFeO3 doped and undoped K0.5Na0.5NbO3-LiSbO3 (KNN-LS) lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique. Phase transition,thermal hysteresis and depolarizing properties of KNN-LS ceramics were investigated. The undoped and doped KNN-LS ceramics were a single orthorhombic phase and mixed phases between orthorhombic and tetragonal phases at room temperature,respectively. BiFeO3 doped KNN-LS ceramic show a dielectric constant-temperature behavior with a thermal hysteresis upon heating/cooling from 300～380℃ which is corresponding to the temperature range of the mixed phase between tetragonal and cubic phases. The planar coupling coefficient kp of all samples decrease with the rising of temperature,and kp≥0.30 when the temperature is below 300℃. The depolarizing temperature of the doped and undoped KNN-LS ceramics is 360 and 370℃,respectively.

Study on Porosities of Quartz/Benzoxazine Composite Fabricated by RTM Process

YIN Chang-ping, XIAO Jia-yu, LI Jian-wei, ZENG Jing-cheng, JIANG Da-zhi

2010, 30(2): 82-88.

[Abstract](1868) [PDF 1476KB](294)

Abstract:
Quartz/benzoxazine composite was fabricated by RTM process.The effect of process parameters on the porosities was investigated compared with those of quartz/barium-phenolic composite. Results show that injection pressure influence porosities of the composites significantly,better sequence of applying injection pressure is low pressure at early stage of the injection process and high pressure at later stage. Injection temperature influence porosities of the composites definitely,optimal injection temperature is the temperature in the range of which the resin viscosity maintains 100 to 500mPa·s. Porosities of composites decrease with the increase of fiber volume fraction. The effects of thickness of the samples on the porosities of the composites is not obviously.Porosities of quartz/benzoxazine composites are much lower than those of quartz/barium-phenolic composites at the same process condition.The porosities of quartz/benzoxazine composite and quartz/barium-phenolic composite reach 0.32% and 3.49% respectively at the given condition,at which applying injection pressure is 1atm at early stage and 4.5atm at later stage,the fiber volume fraction is 50%,the thickness of the composites are 6mm.

Design of Multi-Absorbing Composite Coatings and Thereof

QI yu, HUANG Da-qing, HE shan

2010, 30(2): 89-93.

[Abstract](1766) [PDF 1360KB](277)

Abstract:
Single-absorbing coating generally absorbing a narrow band,and multi-layer absorbing a wide-band radar absorbing paint. Three-tier structure design,broadening the effective absorption band in the absorption frequency of 6~18GHz,the reflectivity of the material is not greater than-10dB,the thickness of the material for 2.15mm,density 4.5kg/m2.Multi-layer absorbing coating,after experienced through a series of environmental tests,still have good performances.

Effect of Height on Mechanical Properties of Metal-rubber

Li Yu-yan, Huang Xie-qing

2010, 30(2): 94-97.

[Abstract](1746) [PDF 1088KB](341)

Abstract:
According to nonlinear constitutive relationship based on porous materials theory,through static experiments for hollow cylinders of metal-rubber,data were fitted,and then relationship between every coefficient in the nonlinear constitutive relationship and height was obtained. The results show that the absolute value of every coefficient in the non-linear constitutive relationship of metal-rubber is greater with the height of the material increasing.Prediction for nonlinear constitutive relationship of metal-rubber was achieved under the condition of constant density,constant loaded area and variational height. Lastly,it was proved by the case that the relationship between every coefficient in the nonlinear constitutive relationship of metal-rubber and height can predict nonlinear constitutive relationship correctly.

2010 Vol. 30, No. 2