航空材料学报

2013, 33(1): .

[Abstract](1157) [PDF 281KB](248)

Abstract:

Influence of Single-Direct and Direct-Reverse SPF on Properties of TC4 Alloy Negative-Angle Parts

SHAO Zong-ke, HUANG Zhong-guo, JIN Shun-yao, LEI Kun, YUAN Qing-hua

2013, 33(1): 1-6.

[Abstract](1478) [PDF 2236KB](336)

Abstract:
The die design of negative-angle part was completed through MARC, and the P-t curves obtained from simulation were modified. Then SPF experiments were done..The thickness distribution of nagative-angle wall and mechanical properties of TC4 alloy parts were studied after single-direct SPF and direct-reverse SPF, and the results were analyzed. The results show the following conclusions. There is a better thickness distribution in arc surface connection than in vertical surface connection. Negative-angle part can be formed through modified P-t curves. In nagative-angle wall the thickness is the smallest. The biggest thinning rate of the part after single-direct SPF is 67% while direct-recerse SPF is 64%, and the thickness distribution standard deviation are 0.186mm and 0.125mm respectively. It shows that direct-reverse SPF not only improves the minimum thickness but also makes the thickness distribution more uniform. The mechanical properties of the part decline due to grain growth which was caused by high temperature steady-state annealing and strain. The hydrogen and oxygen content in direct-reverse SPF part is more than in single-direct SPF part, and the plastic of direct-reverse part decreases more.

Effects of Ag Content on Microstructures and Properties of Al-Cu-Mg Alloy

SONG Yan-fang, PAN Qing-lin, CAO Su-fang, WANG Ying, LI Chen

2013, 33(1): 7-13.

[Abstract](1506) [PDF 2419KB](291)

Abstract:
The effects of Ag content on the mechanical properties and microstructures of Al-Cu-Mg alloy have been studied by Wicker hardness test (HV), room temperature tensile properties, optical microscopy (OM) and transmission electron microscopy (TEM). The results show that as the increase of Ag content, the yield strength and the tensile strength are improved to some extent, and the plasticity is decreased gradually, but it maintains at a high level. In addition, the hardening rate is accelerated, and the peak hardness is increased. The main strengthening phases in Al-Cu-Mg alloy without Ag is ' phase. However, in the alloy with trace Ag it is phase. The number of phase increases gradually with Ag content increasing. The trace Ag promotes the precipitation of phase.

Hot Deformation Behaviour of Ni₃Al-based Alloy with High Al Content

ZHANG Xi-e, FU Shan-shan, LUO He-li, HAN Shao-li, LI Shang-ping

2013, 33(1): 14-20.

[Abstract](1465) [PDF 3137KB](291)

Abstract:
High temperature compression deformation of the Ni3Al-based alloy with high Al content was investigated by thermal simulation machine Gleeble-3800 with the strain rate of 0.01～1 s-1 at 1200～1240℃.Thermal deformation constitutive equation was established for the alloy. The results reveal that the thermal deformation constitutive equation was =28.57(ln+6.72105/RT-44.08) when the strain rate was 0.01s-1 while the thermal deformation constitutive equation was =28.57(ln+1.28106/RT-92.76)when the strain rate was 0.1s-1 and 1s-1. There was only the ' phase re-dissolving to varying degrees, but without the dynamic recrystallization happened.The optimal deformation parameters for the alloy were at the temperature of 1200℃～1215℃, with the strain rate was 0.01s-1. While when the strain rate increased to 1s-1, due to the locked dislocation in the ' phase can not got released, so the /' interface was liable to be cracked on the area of single ' phase, and that deformation condition was corresponded to the destabilization area.

Numerical Simulation for Canning Extrusion Process of FGH96

ZHU Xing-lin, LIU Dong, YANG Yan-hui, NIU Guan-mei

2013, 33(1): 21-27.

[Abstract](1575) [PDF 1943KB](311)

Abstract:
The configuration and dimension of the die are critical for canning extrusion of FGH96 P/M superalloy. In this paper, the influence of die angle, band length and entrance fillet of the dies on the canning integrality,extrusion ratio of the core,and extrusion force were analyzed comprehensively by using FEM and orthogonal method. The results of FEM numerical simulation and orthogonal analysis indicate that the integrality of canning and extrusion ratio of the core were improved with the decrease in die angle, band length and increase in entrance fillet of the die. The optimal combination of the structural parameters of the extrusion die was obtained.

Influence of Geometrical Features of Stir Pins on Temperature Distributions within Workpiece during Friction Stir Welding of Aluminum Alloys

LI Jing-yong, KANG Xiao-liang, ZHAO Yang-yang

2013, 33(1): 28-32.

[Abstract](1610) [PDF 1923KB](311)

Abstract:
The temperature distributions in the specimens of aluminum alloy are measured during friction stir welding (FSW) while friction stir tools with different geometrical features were used. The effect of shoulder dimension and the shape of stirring pin on the temperature distributions are analyzed. It is indicated that the larger the shoulder dimension of stirring tool, the higher temperature in specimens welded. The shape of stirring pins has significant impact on the temperature distribution in the initial stage of FSW. In the stable stage of welding process, the temperature of specimen was influenced by the plastic flow of the weld metal while stirring pins with different shape were applied. The temperature of specimens is highest with column-shaped pin, lower with circular truncated cone-shaped pin, and lowest with screw-shaped pin. A quadratic polynomial describing the temperature distribution in width direction of workpieces welded with column-shaped pin was obtained by regression analyzing the experimental data.

Effect of Cooling Medium on Microstructure and Property of AZ31 Magnesium Alloy in Friction Stir Processing

WANG Kuai-she, GUO Qiang, WANG Wen, GUO Wei, WU Nan

2013, 33(1): 33-37.

[Abstract](1381) [PDF 1773KB](309)

Abstract:
Friction stir process was applied to AZ31 magnesium alloy in the air, circulating water and mixture of dry ice and methanol respectively. The effect of cooling medium on microstructure and property of AZ31 magnesium alloy in friction stir process was studied in this paper. The results show that the peak temperature and duration of above 150℃ during friction stir processing are descending orderly in accordance with the order of the air, circulating water and mixture of dry ice and methanol. The impact which cooling medium inhibits growth of grain is obvious. The grain sizes of stir zone in the air, circulating water and mixture of dry ice and methanol are 3.9, 3.0 and 1.8 m respectively. Furthermore, the grain size and peak temperature have the same changing trend. Due to the dominant function of gain boundary sliding, the hardness and strength of the stir zone in the mixture of dry ice and methanol are lower than that they are in the circulating water, and the elongation is highest. In the cooling mediums of the air and the circulating water, both tensile fractures exhibit quasi-cleavage crack, but the possessive proportion of cleavage crack in the circulating water is significantly higher than it in the air, the tensile fracture in the mixture of dry ice and methanol exhibits a typical ductile dimple-fracture.

Computer Optimization of Excitation Frequency for Plasma Ultrasonic-Arc Welding of Super Alloy MGH956

XIE Wei-feng, LEI Yu-cheng, REN Wen-jie

2013, 33(1): 38-44.

[Abstract](1424) [PDF 3205KB](261)

Abstract:
With considering the characteristics of plasma arc welding and using double ellipsoid heat source model, the welding temperature field are analyzed and 3D molten pool model was established. The mode calculation of molten pool under action of 0Hz ultrasonic-arc was conducted within the optimal frequency range and the response corresponding to modal frequency was further analyzed. Finally, three groups of 2.0 mm MGH956 alloy plates with different ultrasonic-arc frequencies were welded. The results show that the predicted geometry and locus of the fusion line in the plasma ultrasonic-arc welding weld cross-section are in good conformance with the experimental measurements. When the ultrasonic-arc frequency is equal to natural frequency of molten pool, the area of welded zone increases in depth direction, the weld structure refined is optimal, the porosity is the lowest and the softening phenomenon in welded zone improves dramatically. Using this method, the purpose of optimizing the ultrasonic-arc frequency has basically achieved.

Analysis of Mechanical Properties about the Welding Joints of 2219 Aluminum Alloy

ZHANG Dan, CHEN Wen-hua, SUN Yao-hua, DONG Feng-bo

2013, 33(1): 45-49.

[Abstract](1531) [PDF 2264KB](302)

Abstract:
Electron beam welds, Friction stir welding and gas tungsten arc welds of aluminum alloy 2219 were made and their mechanical properties were compared by tensile testing and micro-hardness. The reasons for the difference of mechanical properties were researched by scanning electron microscopy and optical microscope. It is shown that the tensile strength of EBW joints is about 79% of base metal and hardness of the joints reaches 97HV. The tensile strength of FSW joints is about 74% of base metal and hardness of the joints reaches 97.6HV. But the tensile strength of TIG joints is only about 53% of base metal and hardness of the joints reaches 72HV. The EBW joints and the FSW joints had better performances than the TIG joints. According to the microstructures, fracture and section morphology analysis, fine equiaxed grains, distribution more evenly of copper elements and less defects that the EBW joints and the FSW joints have are the main reasons for superior mechanical properties.

Effect of Milling Mediums on Nano-Sb Powders Prepared by Ball Milling

XU Jian-lin, GUO Qiang, GAO Wei, KANG Zhao, XI Guo-qiang, ZHANG Liang

2013, 33(1): 50-55.

[Abstract](1468) [PDF 1589KB](346)

Abstract:
The effect of milling mediums on nano-Sb powder prepared by ball milling was explored. Taking Sb powder of 250m as raw material, some different Sb powder was synthesized by mechanical ball milling in the course of dry grinding or wet grinding with different additives as milling mediums respectively. Crystalline phases, morphology and particle size of Sb powder samples were characterized by XRD, TEM and FT-IR. Results show that different milling mediums play different role in the preparing process of nano-Sb powder by using ball milling method. There is oxidation phenomenon of Sb powder in the preparing of dry grinding,while pure nano-Sb particles can be prepared by ball milling with some milling mediums. When the milling medium is distilled water, Sb powder can be prevented from oxidating effectively, however, its dispersion is low. The Sb powder prepared with milling mediums of distilled water and sodium dodecyl sulfate is higher dispersibility, which has a wide distribution of particle size. When the milling mediums of distilled water and OP-10 were used, the resulting nano-Sb powder is evenly dispersed, which has a narrow distribution of particle size and an average particle size of 20 nm.

Effect of Addition of TaC on Properties of Ti₃SiC₂ Ceramics

YANG Yi-nuo, YIN Hong-feng, LIU Bai-kuan, YUAN Hu-die, JIA Huan

2013, 33(1): 56-60.

[Abstract](1582) [PDF 2005KB](257)

Abstract:
The material of 20%(mass fraction, same below) TaC/Ti3SiC2 was prepared by reactive hot pressing method. The phase constituent, mechanical properties and oxidation resistance were investigated. The results showed that:(1) The densification, flexural strength and fracture toughness of 20%TaC/Ti3SiC2 increase with the increase of hot pressing temperature; (2) The oxidation resistance of 20% TaC/Ti3SiC2 is much higher than that of monolithic Ti3SiC2 and 20% SiC/Ti3SiC2 composites; (3) The oxidized layers of TaC/Ti3SiC2 are composed of two layers. The outer layer is TiO2. And the inner layer is the mixture of TiO2, SiO2 and the eutectoid of TiO2 and Ta2O5.

Synthesis of POSS-Diamine and Its Modification Researches on Polyimide Materials

LEI Xing-feng, ZHANG Qiu-yu, SUN Jiu-li, ZHANG Bao-liang, CHEN Shao-jie, FAN Xin-long, LI Xiang-jie

2013, 33(1): 61-67.

[Abstract](1651) [PDF 1746KB](314)

Abstract:
In this paper, -aminopropyltriethoxysilanes (APS) and penyltriethoxysilanes (PTES) were adopted to prepare bifunctionalized amino POSS, namely POSS-diamine, via hydrolytic co-condensation in ethanol/H2O solvent under the catalysis of TEAOH. The structure of the product was characterized by FTIR, 1H-NMR, 13C-NMR and 29Si-NMR, which revealed that the structure of the product was ideal. POSS-diamine and ODA were used to react with PMDA to prepare POSS modified polyamic acid. After thermal imidization process, a series of polyimide hybrid films with different POSS-diamine content were obtained. The thermostability, mechanical properties and atomic oxygen corrosion resistance property of hybrid films were measured by TGA, tensile testing machine and plasma atomic oxygen producer. Results indicated that thermal property of these hybrid films was still excellent, while mechanical performance slightly decreased. The atomic oxygen resistance property was improved nearly four times when POSS-diamine addition reached 7(mol)%.

Preparation and characterization of Graphene Nanosheets/High Density Polyethylene Conductive Composites

DU Yan, JI Tie-zheng, ZHANG Jiao-qing, TANG Ting, YANG Jian-feng, ZHENG Xing-zhuo

2013, 33(1): 68-71.

[Abstract](1577) [PDF 964KB](440)

Abstract:
Graphene nanosheets (GNS) was prepared by chemical oxidation-reduction method. And Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) was used to characterize graphene oxide (GO) and GNS. GNS/high density polyethylene (HDPE) composite were prepared through solution mixing. The electrical properties of these composites were investigated. Percolation in GNS/HDPE composites occurs when the filler concentration is near 4.3% (mass fraition, same below). The resistivity didn't change much when the weight fraction was above 6.5 (mass fraition, same below)%. DSC analysis reveals that the crystallization behavior of PE was significantly altered by addition of GNS, crystallization shifts to higher temperature during cooling, which indicates that GNS induces heterogeneous crystallization of PE.

Structural Evolution Analysis of PAN Carbon Fiber During Preparation Process Using Radial Distribution Function Based on XRD

LIN Xue, WANG Cheng-guo, YU Mei-jie, XU Yong, LIN Zhi-tao, ZHANG Shan

2013, 33(1): 72-77.

[Abstract](1535) [PDF 1374KB](270)

Abstract:
The structural evolution of PAN carbon fiber during preparation process was studied by using the X-ray Diffraction and radial distribution function. The results show that the graphite-like structure exists in the PAN fiber, which is the important basis of graphite microcrystalline structure. The nearest neighbor distance of PAN is 0.688 nm. The third neighboring distances of all carbon fibers are greater than that of graphite, indicating that planar six-member rings of graphene sheet are not formed between 500℃ and 1250℃. The structure of fibers transforms from long-range order to long-range disorder, and then from short-range order to long-range order during the whole preparation process of carbon fiber.

Correlation between Microstructure and Mechanical Properties of PAN-based Carbon Fiber

JING Min, TAN Ting-ting, WANG Cheng-guo, FENG Zhi-hai, YANG Yun-hua

2013, 33(1): 78-85.

[Abstract](1736) [PDF 2968KB](378)

Abstract:
The micro-structures of 4 three kinds of carbon fiber products of T300, T700SC and T800HB were characterized by using scanning electron microscope, X-ray diffractometer and small angle X-ray scattering system. The micro-structure information was obtained including the fibril structure reflected by the surface groove morphology, the graphic micro-crystal size and orientation degree, the micro-pore size. The experimental results show that the mechanical properties of the carbon fiber are not determined by some micro-structure characterization, but an expression of all micro-structure characterization. The mechanical properties of T300 are the worst among the three kinds of carbon fibers. Its five micro-structure parameters are all the worst. The diameter of T700S is little smaller than that of T300, however, its structure is compacter and defects are less, it is the reason that why the tensile strength, the tensile modulus and the elongation of T700S are higher. Although the fibril structure of T800H is not better than that of T700S, its filament diameter, shear fracture morphology, graphic micro-crystal orientation degree and micro-pore size is better than that of T700S, which causes that its tensile strength, tensile modulus and density are higher than T700S. However, the larger graphic crystal size of T800 can cause the decreasing of the plasticity along axial direction. Therefore, the elongation of T800H is little smaller than that of T700S.

Experimental Investigation of Tensile Behavior of Hybrid Laminates Repaired by Scarfing Method Based on k-sample Anderson-Darling Test

LIU Sui, GUAN Zhi-dong, GUO Xia, XUE Bin, XI Guo-fen, CAI Jing

2013, 33(1): 86-92.

[Abstract](1549) [PDF 2072KB](248)

Abstract:
Experimental study on tensile behavior of hybrid plain woven fabric laminate repaired by scarfing method was conducted in the paper. In order to analyze experimental results, k-sample Anderson-Darling test was adopted in the study to investigate the influence of scarf ratio, repair methods and initial damage diameters to the tensile behaviors of repaired specimens. Experimental results indicate scarfing repair can recover the tensile strength of laminate well. After thorough comparison, the study demonstrates that the tensile strength of full depth scarfing specimen can achieve the level of intact panel when scarf ratio exceeds 1:20 and for half depth scarfing specimen, the threshold of scarf ratio is 1:10.Test results also reveal when the scarf ratio is fixed, changing the diameter of initial damage could hardly affect the tensile strength and failure mode of scarfing repaired specimens. Conclusions of the investigation provide insight into scarfing repair design method on hybrid plain woven fabric laminate.

Experimental and Numerical Study of Progressive Failure of Ductile Metals

LIU Chao, SUN Qin, LIU Yan-jie, FAN Xue-ling

2013, 33(1): 93-99.

[Abstract](1580) [PDF 2355KB](355)

Abstract:
The investigation of progressive failure of ductile metals is valuable for accelerating the application of ductile metals and reducing the physical experiments burden. In this paper, a modified three-stress-invariant ductile fracture model is proposed based on continuum damage mechanics, where the effects of hydrostatic pressure and Lode angle on damage variable are considered. To predict the progressive failure behavior of ductile metals, a series of experiments have been conducted for high strength aluminum 2A12-T4 sheets and the proposed model is implemented into quasi-static finite element method through a compilation of user's material subroutine VUMAT of the commercial finite element platform ABAQUS. The ductile fracture model is validated by comparing between experimental data and numerical results. It is shown that the proposed ductile fracture model can accurately and effectively predict the whole damage process of ductile metals including crack initiation, propagation and final fracture.

Investigation on Low Cycle Fatigue Properties of Superalloy GH3044 at Elevated Temperature

ZHANG Shi-chao, YU Hui-chen, LI Ying

2013, 33(1): 100-104.

[Abstract](1636) [PDF 1625KB](278)

Abstract:
Low cycle fatigue(LCF)tests of nickel-base superalloy GH3044 were conducted under total axial strain control at 600℃. The specimens were tested under fully reversed strain. The life prediction capability of Manson-Coffin equation, Three-parameter power function and Ostergren model were evaluated by the LCF data. The results indicated that the alloy exhibited cyclic hardening behavior at 600℃, which could explain by the interactions between dislocations or dislocation and precipitates during cyclic deformation. The fatigue parameters were obtained by analyzing its cyclic stress-strains curves and strain-life curves. SEM observations indicated that LCF cracks initiated predominantly on the surface of specimen. Once initiated, cracks would propagate perpendicularly to the loading direction and the specimens exhibited dimple fracture. The results of life prediction showed Ostergren model gave better results with the smaller scatter band and standard deviation than Manson-Coffin equation and three-parameter power function.

2013 Vol. 33, No. 1