航空材料学报

Characteristics of High Nb Containing TiAl Alloyed Powders by Radio Frequency Plasma Processing

LU Xin, WANG Shu-chao, ZHU Lang-ping, HE Xin-bo, HAO Jun-jie, QU Xuan-hui

2011, 31(4): 1-6.

[Abstract](1348) [PDF 1189KB](237)

Abstract:
Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y(at%) ingot was prepared using a vacuum induction furnace,and then machined with a crusher in argon atmosphere.Subsequently,microfine spherical high Nb containing TiAl alloyed powders were obtained by fluidized bed jet milling in inert gas and then by radio frequency argon plasma.The fabrication process and characteristics of the powders were investigated.The results show that the powders fabricated by this process is highly refined and spheroidized,and the particle size is accurately controlled in a small interval.The plasma-spheroidized powders are dominated by α2-Ti3Al with a minor amount of β-Ti2AlNb.The oxygen content becomes higher gradually with the decrease of the particle size.The exterior and interior microstructures of the alloyed powders strongly depend on the particle size.The powders with an average particle size of 90μm show dendritic microstructure,and network Al-rich phase segregation exists within the particles.With the particle size decreasing,the surface of the powders tends to be smooth,and the internal segregation is gradually weakened.In addition,the 90μm powders possess high composition homogeneity,and with the decrease of the particle size the composition homogeneity declines gradually.

Molecular Dynamics Simulation on Thermal Boundary Resistance of Superlattice Structure

ZHANG Xing-li, SUN Zhao-wei

2011, 31(4): 7-10.

[Abstract](1359) [PDF 487KB](288)

Abstract:
Non-equilibrium molecular dynamics(NEMD) simulations were performed to calculate the interface thermal boundary resistance of Si/Ge superlattice structure.The simulation results show that the thermal boundary resistances of interfaces closest to the hot bath are likely to control the heat transport capability of the structure system.The effects of period thickness and temperature on thermal boundary resistances were also obtained by the simulation.The thermal boundary resistances decrease with the increase in the period thickness of the structure,and the heat transport capability is enhanced for that.The effects of inelastic scattering at the interfaces lead to a reduction in the overall thermal boundary resistances for the system with an increase in temperature.

Fabrication of Submicron NiAl-Al₂O₃ Composite and ItsSinter-Forging with Short Process

XU Gui-hua, LU Zhen, ZHANG Kai-feng

2011, 31(4): 11-17.

[Abstract](1286) [PDF 1239KB](385)

Abstract:
Taking Ni and Al powders as raw materials,NiAl-5vol% Al2O3 composite was prepared by mechanical alloying and hot-pressed sintering,and a model of leading edge was subsequently fabricated by sinter-forging process.By mechanical alloying,the powders were refined and NiAl-5vol%Al2O3 was synthesized through in-situ reaction.Dense NiAl-Al2O3 composite was consolidated through hot-pressed sintering at 1300℃.It was observed that Al2O3 particles homogeneously distributed in NiAl matrix in the form of "intragranular structure"and "intergranular structure".The average sizes of NiAl and Al2O3 are 400nm and 100nm respectively.Compared with fine grained NiAl,the fracture toughness and compression performance are both obviously improved.The leading edge was fabricated by sinter-forging process,which is characterized by fine grains and high surface quality,and its Vickers hardness is up to 575HV.

Formation Law of Microporosity in GH4169 Alloy Vacuum Arc Remelting Ingot and Influence of Melting Rate

LIU Yan-mei, CHEN Guo-sheng, WANG Qing-zeng, SUN Wen-ru, LIU Jun-he, LOU Jian-xin, HU Zhuang-qi

2011, 31(4): 18-23.

[Abstract](1253) [PDF 1101KB](211)

Abstract:
The effects of melting rate on the microstructure and microporosity formation of GH4169 alloy VAR(vacuum arc remelting) ingots have been studied by using metallographic microscope and scanning electron microscope,and its effects on the area percent of microporosity of the ingots was also analyzed quantitatively by the metallographic image analysis software.The results show that the microporosity formed in the chilled layer at the surface of the ingot possesses a harsh surface due to the existing of metal particles on the mold caused by sputter or vapor coagulation.The micropores formed at the edge part under the chilled layer tend to appear with a round shape and smooth surface,and hence it might inherit the shape of pores formed by the ease of gas element such as N from the liquid.The pore size is small and its density is largely reduced compared with that in the chilled layer.In the centre of ingot,the size and density of the microporosity are greatly increased,which is distributed along the interdendritic area,because the elements congregation here is serious and the secondary or tertiary dendrites are well developed which blocks the liquid passage.With the increasing of the melting rate,the formation of the microporosity especially at the center of the ingot is increased significantly,because the depth of the liquid pool is increased,the dendrites tend to grow horizontally,the secondary and tertiary dendrites are developed further,and the elements congregation is more serious.

Effect of High Magnetic Field on Precipitating Phase Al₂Cu in Al-40%Cu Alloy

ZHANG Tian-hui, JIN Fang-wei, REN Zhong-ming, XUN Ren-ping

2011, 31(4): 24-28.

[Abstract](1406) [PDF 725KB](404)

Abstract:
Al-40%Cu Alloy was prepared under a high magnetic field.The solidification behavior of Al-40%Cu alloy was studied by optical microscope.The experimental results show that the precipitating phase Al2Cu formed alignment planar layer structure having a angle with the direction of magnetic field when Al-40%Cu alloy solidified under a high magnetic field of 10T.The theoretical analysis demonstrates that Al2Cu crystals occur a rotation under the action of the magnetic moment caused by the susceptibility difference on different direction in the applied field,and the easy magnetization axis rotates to a direction of the lowest energy.Furthermore,the interaction among the particles can touch the order of the intermolecular force of liquor under a high magnetic field.The neighboring Al2Cu grains approach each other and grow along the easy magnetization direction due to the magnetic interaction,and then the alignment structure has been formed in the applied field.

FGH95-K418B Dual Alloy HIP Diffusion Bonding Process

LUO Xue-jun, MA Guo-jun, WANG Xiao-feng, TIAN Gao-feng, GAI Qi-dong, MU Song-lin

2011, 31(4): 29-32.

[Abstract](1298) [PDF 771KB](209)

Abstract:
The development of HIP diffusion bonding of P/M superalloy FGH95 powder and K418B cast blade materials has been explored.The effects of HIP bonding process on elements diffusion and precipitation at FGH95-K418B interface were discussed.The variations of microstructure and mechanical properties of K418B cast blade materials after hipping have also been investigated.The results show that the perfect diffusion and bonding at powder-blade materials interface can be achieved by proper control,and the properties of K418B materials can also be maintained up to the desired level after HIP diffusion bonding.

Microstructures and Properties of MGH956 Sheet Joints with EB and TIG Welding Methods

TIAN Yun, GUO Wan-lin, YANG Zheng, HUAI Jun-feng, LIU Guang-zu, LI Wen-ling, LI Shuai-hua

2011, 31(4): 33-38.

[Abstract](1297) [PDF 1217KB](270)

Abstract:
The microstructures of MGH956 sheet joints welded by EB and TIG methods and tensile properties from room temperature to 1100℃ were studied.Results showed that the dispersoids,which were superfine in original alloy matrix,coarsened obviously after undergoing welding cycle.More coarse grains with the orientation perpendicular to that of the base alloy were formed and holes were left inevitably within joint microstructures.The changes in microstructure resulted in both the significant decrease of joint's high temperature(above 800℃) strength and the much higher brittleness at low temperature.Based on the comparison of the microstructures and tensile properties of the joints welded using EB to that of joints using TIG,it is verified that EB has more advantage than TIG for the welding of MGH956 sheet,and thus EB possesses the engineering potential.

Investigation of Sliding Wear Characteristics of Vacuum-carburized,Duplex-hardened and Plasma-Sulfurized 13Cr4Mo4Ni4VA Steel

JIANG Zhi-hua, TONG Xiao-jun, SUN Feng, LI Zhi, WANG Zi-jun, SHI Lian-wei

2011, 31(4): 39-44.

[Abstract](1313) [PDF 1230KB](218)

Abstract:
Duplex hardening,vacuum carburizing and plasma sulfurizing of 13Cr4Mo4Ni4VA steel were carried out,and then the functionally gradient layers were prepared.Sliding wear experimental study was carried out for carburized,duplex hardened and sulfurized 13Cr4Mo4Ni4VA steel.The corresponding case microstructure and worn surface morphology were observed to explore the anti-friction and wear-resistance mechanism.The results show that the duplex hardening of 13Cr4Mo4Ni4VA steel leads to superior surface hardness(70HRC),good microstructure and gradient distribution,high level of resistance to plastic deformation,holding excellent antifriction and wear-resistance performance.All the plasma sulfurized layers(supported by carburized or duplex hardened layer) with different depth were of outstanding self-lubricating performance,and varied anti-friction mechanisms of sulfurized layer worked.However,too deeper sulfurized layer leads to inferior property of wear resistance.

Effects of Hole Cold-Expansion on Microstructure and Fatigue Property of 7B50-T7451 Aluminum Alloy Plate

GONG Peng, ZHENG Lin-bin, ZHANG Kun, YI Lin-na, SONG De-yu

2011, 31(4): 45-50.

[Abstract](1419) [PDF 1094KB](242)

Abstract:
Cold hole-expansion was employed on the work of 7B50-T7451 aluminum alloy plate by using a mandrel.The effects of cold hole-expansion on the fatigue life and microstructures of 7B50-T7451 specimens were analyzed by fatigue tests under cyclic loading,and the results were compared with cold-worked holes of 7050-T7451 thick plate.The fatigue striation spacing was observed and measured by SEM.The magnitude of the residual stresses and dislocations introduced into the specimens by hole-expansion were evaluated by an X-ray diffraction and TEM methods.The results show that the 7B50-T7451 aluminum alloy obtained good fatigue enhancement effect with the shrink range of 4%~6% and the fatigue lifetime were improved up to 29 times compared to the non-cold-expanded ones.The depth of strengthening layer was about 7.3mm,and the maximum residual compressive stress of 387MPa was observed at a distance of 1mm to the border of the hole.The residual compressive stress and dislocation cell structure around the cold-worked holes retard the fatigue crack growth rate in propagation stages,and then the whole fatigue life is increased.

Effect of Arc Current on Microstructure and Mechanical Properties of CrN Coatings Deposited by Arc Ion Plating

ZHENG Chen-chao, CHEN Kang-min, ZHANG Xiao-ning, HUANG Yan, GUAN Qing-feng, GONG Lei, SUN Chao

2011, 31(4): 51-55.

[Abstract](1271) [PDF 693KB](252)

Abstract:
CrN coatings were deposited on the Ti-6Al-4V substrate by arc ion plating process.Scanning electron microscopy(SEM),X-ray diffraction(XRD) and transmission electron microscopy(TEM) were used to analyze the microstructure of deposited CrN coatings.Mechanical properties of deposited CrN coatings were also measured.The results show that the deposition rate of CrN coatings increases,the number and the size of macro-particles also increase,and the surfaces of the coatings become rough significantly with the increase of arc current.Single-phase CrN coatings were deposited with different arc current.The changing of arc current affects the bombardment of electrical particles and the energy states of the surfaces.It was also observed that preferred orientation of CrN coatings changed from(111) to(200) and(220).Hardness of CrN coatings increases and then decreases with the increase of arc current,but the adhesion and friction of CrN coatings coefficient increase.CrN coating of smaller structure which exhibits higher deposition rate and lower deposition temperature was obtained at arc current of 65A.

Design,Manufacturing and Testing of Composite Wing Model via Integral Forming Process

LUO Chu-yang, YI Xiao-su, LI Wei-dong, ZHOU Yu-jing, ZHU Yi-gang, LIU Gang

2011, 31(4): 56-63.

[Abstract](1459) [PDF 1356KB](423)

Abstract:
Four different structure wings were designed according to the given configuration.Based on the optimized curing process of the resin,the four composite wing models were manufactured via integral forming technique.The three point bending test results show that the I-beam wing has the highest load-carrying efficiency,then the following is the C-beam wing.The skin-foam wing has the minimum load-carrying efficiency.The failure of skin-foam wing is caused by compression failure of upper skin at loading point,while the skin-stiffened wing is failures from the shear break of support point.The C-beam and I-beam structure wings both have shear failures at the wing leading edge between loading point and support point.The finite element analysis(FEA) result is consistent well with those of experiment.

Experimental Research on Fiber Compaction of L-shaped Stiffeners in Stiffened Skins by Autoclave Process

WANG Xue-ming, XIE Fu-yuan, LI Min, ZHANG Zuo-guang

2011, 31(4): 64-68.

[Abstract](1287) [PDF 873KB](282)

Abstract:
L-shaped stiffeners were fabricated by integral co-bonding technique in the autoclave.This study focused on investigating the influence of tool assembly,filler,curvature radius and bleeding process on the fiber compaction and manufacturing defects of L-shaped stiffeners,with analyzing the formation mechanism of these defects.The results indicated that non-uniform thickness,bridging and rich resin were the main defects of L-shaped stiffeners.The fiber compaction was improved significantly on the condition that the pressure in corner section was increased by applying flexible tools and rolling unidirectional prepregs as fillers into the stiffener core,and that the corner effect was remarkably caused a decrease by increasing curvature radius and applying pre-bleeding process.All these results are the vital importance for declaring the formation mechanism of defects and enhancing integral manufacturing quality of composite stiffened skins.

Thermodynamic Property of Shape Memory Epoxy Resin Modified with 6F-PEEK

GAO Jun-peng, HE Xian-cheng, AN Xue-feng, ZHANG Chen-qian, YI Xiao-su, DANG Guo-dong, CHEN Chun-hai

2011, 31(4): 69-73.

[Abstract](1415) [PDF 509KB](297)

Abstract:
The dynamic mechanics and phase separation behavior of epoxy with shape memory modified by fluorinated poly(ether ether ketone) terminated with —OH(6F-PEEK) was characterized by DMA and SEM respectively.DMA result shows that there are two glass transition temperatures in this material.The cured epoxy phase showing high Tg of 223℃ acts as hard-segment-forming phase and is responsible for the permanent shape.6F-PEEK is used as switching phase for a thermally induced shape-memory effect.At the transition temperature of 150℃,the chains of 6F-PEEK are moved,while the chains of cured epoxy are frozen,resulted in the shape memory effect of the blends.The bending angle of the resin was increased with increasing the content of 6F-PEEK.

Effect of Chain Extender on Properties of Transparent Thermoplastic Polyurethane Elastomers

HOU Jun-xian, LI Lei, LIU Wei-dong, YAN Yue, CHEN Xiang-bao

2011, 31(4): 74-80.

[Abstract](1515) [PDF 1010KB](399)

Abstract:
Various segmented transparent polyurethanes were prepared from dicyclohexylmethane diisocyanate(H12MDI),polytetramethylene glycol(PTMEG) with an Mn of 1000,and aliphatic diols as chain extenders by a standard prepolymer synthesis process.The effect of the structure of chain extender on the mechanical properties,peel adhesion properties and optical properties was investigated.The freshly exposed PU and PMMA adhesion failure surface was analyzed by XPS and AFM.With the increase of hard segment length,the tensile strength,peel strength and shore A hardness of the H12MDI based elastomer decrease and the elongation at break increases.The length of chain extender has little effect on the transparency of PU.Transesterification reaction exists in the interfacial region.

Lubricity of Fluorosilicone

JIANG Ke-juan, ZHANG Xu

2011, 31(4): 81-85.

[Abstract](1188) [PDF 728KB](359)

Abstract:
The four-ball lubricity of fluorosilicone containing γ-trifluoropropyl was studied.The results show that it is not as good as ester-based oil.The lubricity of fluorosilicone is improved through blending additives in or to improve the molecular structure on base stock.The common compounds including chlorine and phosphorus increase the lubricity of fluorosilicone,but the poor solubility in fluorosilicone is showed.Through inserting Cl to γ-trifluoropropyl chain of fluorosilicone,the lubricity is improved markedly,its extreme load characteristic is better than ester-based lubricating oil.This case is examined by gear test.The Cl-fluorosilicone also has excellent high temperature oxidation stability,and has no corrosiveness to metals.

Model of Two-parameter Driving Force for Fatigue Crack Growth of PMMA

SONG Quan-chao, ZHANG Jian-guo, YI Xiao-wei, WANG Hong

2011, 31(4): 86-89.

[Abstract](1273) [PDF 419KB](194)

Abstract:
The fatigue crack propagation rate of YB-DM-11 PMMA in intermediate and accelerated regions was measured with the R-ratio of-0.4,0.1,and 0.4.The two-parameter driving force model,K*=(Kmax)α(ΔK+)1-α,which apply to metal materials,was introduced to describe the crack propagation behavior of PMMA.For PMMA,the parameter α is not a fixed value but a function is related to stress ratio,fracture toughness,stress intensity factor and α1,which is calculated while the crack propagation rate is tending to infinity.To R=-0.4— 0.4,the common crack propagation rate equation based on the two-parameter driving force model was obtained,and was used to explain the fatigue crack propagation behavior under different stress ratios,and predicted the fatigue crack propagation rate of PMMA in intermediate and accelerated regions was effected by the stress ratios.

Experimental Studies on Compressive Properties of Composite Z-pins

WANG Xiao-xu, CHEN Li

2011, 31(4): 90-95.

[Abstract](1307) [PDF 642KB](285)

Abstract:
The axial compressive behavior of three kinds of composite Z-pins was investigated.The ultimate compressive stress and failure modes of composite Z-pins with different length were analyzed.The results show that carbon fiber Z-pins with the diameter of 0.50mm have the best compressive properties.Those with the diameter of 0.28mm are apt to be buckled.And aramid fiber Z-pins are easily failures on the contact point.Theoretical predictions of critical stress of carbon fiber Z-pins agree well with the experimental results,but the experimental value of the critical stress value of aramid fiber Z-pins is lower than the theoretical value.

2011 Vol. 31, No. 4