航空材料学报

Orthogonal test study of formability for 2D12 aluminium alloy after pre-stretching and solution heat-treatment

GAO Hongzhi, ZHOU Xianbin, LI Dongsheng

2004, 24(4): 1-7.

[Abstract](1410) [PDF 296KB](328)

Abstract:
The formability of 2D12 aluminium alloy after pre-stretching and solution heat treatment has influenced the improvement of forming process and the application of numerical simulation. Based on the practical forming process of 2D12 aluminium alloy after pre-stretching and solution heat treatment, an orthogonal test was developed to investigate the influence of pre-stretching before heat treatment, orientation of specimen to rolling direction,age hardening time and sheet thickness on the behavior and formability of 2D12 aluminium alloy after pre-stretching and solution heat treatment. The paper indicates that the yield strength increases and strain hardening exponent decreases as pre-stretching and aging hardening time increases. Additionally anisotropy(i.e. variation in yield strength and R-ratio with direction) is not affected by pre-stretching and aging hardening time. The result may help sheet forming process design and numerical simulation.

A study of homogenization processes for a new type anticorrosion aluminum alloy

JIANG Haifeng, WANG Shengqiang, LU Zheng, DAI Shenglong, LU Jian, HUANG Min

2004, 24(4): 8-10.

[Abstract](1508) [PDF 619KB](226)

Abstract:
The homogenization processes technology of a anticorrosion Al alloy is recommended.For its feature,the homogenization technology is studied that capability of alloy is improved.The homogenization system is established by a great deal of technique experiments for a new type anticorrosion aluminum ingot.The foundation which preferably integrated capability is obtained by great deformation for the new type anticorrosion aluminum alloy is established.

High temperature deformation behavior of TC21 alloy

FENG Liang, QU Henglei, ZHAO Yongqing, LI Hui, ZHANG Yingnan, ZENG Weidong

2004, 24(4): 11-13.

[Abstract](1548) [PDF 178KB](465)

Abstract:
By thermo-simulation experiment, high temperature deformation characteristics of TC21 titanium alloy are investigated within temperature range of 900～1100℃ and strain rate range of 0.01～50s-1.Constitutive equations are established. Test results show that the deformation mechanisms of TC21 alloy exhibit dynamic recovery feature within high temperature region and grain boundary slip behaviors in low temperature case, where β phase transus is the mechanism conversion point. Deformation activation energy values are 330.57 kJ/mol in(α+β)region,and 176.49 kJ/mol in β region respectively.

Comparison of properties of 9SiCr alloy steel in various quenching media after quenching

CHENG Heming, XIE Jianbin, LI Jianyun

2004, 24(4): 14-17.

[Abstract](1512) [PDF 555KB](405)

Abstract:
The mechanical properties and microstructure of 9SiCr alloy steel after quenching in various quenching media were investigated. The results showed that(1) the temperature differences between center and surface of cylinder were: the largest during water quenching, the lower during oil quenching and the lowest during gas quenching;(2) the temperature gradient of work-piece is smaller during gas quenching, it can be predicted that corresponding thermal strain and distortion is also smaller than that during water and oil quenching;(3) the gas quenching technology in proper pressure can be realized for good hardenability 9SiCr alloy steel.

Microstructure changes and residual stresses of each phase caused by shot peening in 304 austenitic stainless steel

GAO Yukui

2004, 24(4): 18-21.

[Abstract](1431) [PDF 553KB](526)

Abstract:
The phase transformation and residual stress induced by shot peening in 304 austenitic stainless steel were investigated. The volume fraction of austenite phase and martensite phase and residual stress of each phase were determined quantitatively by X-ray diffraction technique. The results indicate that volume fraction of austenite phase and martensite phase is function of peening intensity and peening time and that volume fraction of martensite phase increases with time of shot peening. The time to shot peening and peening intensity are two main parameters when peening 304 austenitic stainless steel, the saturated time to ensure 100% coverage is not enough to ensure the maximum volume fraction of martensite phase caused by shot peening under the same peening intensity.

The effects of deposition temperature on the depositon rates and structures of CVD SiC coatings

LIU Rongjun, ZHANG Changrui, LIU Xiaoyang, ZHOU Xingui, CAO Yingbin

2004, 24(4): 22-26.

[Abstract](1540) [PDF 265KB](556)

Abstract:
CVD SiC coatings were prepared by CH3SiCl3-H2 system at temperature from 1000～1300℃.The effects of deposition temperature on the deposition rates of SiC coatings was studied and the micro-structures of CVD SiC coatings were accounted by using the principles of auto-nuclei. The results show that the control mechanism of CVD SiC coatings can be divided into two parts: chemistry reaction in the 1000～1200℃ region and diffusion reactions in the 1200～1300℃ region. SiC coatings deposited at 1000℃ and 1100℃ are dense as well as smooth, whereas those which deposited at 1200℃ and 1300℃ become loose and rough .The XRD diffraction peaks of the as-deposited coatings become integrate as deposition temperature increase, a small amount of α-SiC appear in the XRD patterns when the deposition temperature exceeds 1150℃.

Research on combining performance between the C/SiC composites and CVD SiC coating

ZHANG Yudi, ZHANG Changrui, LIU Rongjun, LIU Xiaoyang

2004, 24(4): 27-29.

[Abstract](1403) [PDF 155KB](506)

Abstract:
C/SiC composites was prepared by ways of polymer infiltration pyrolysis(PIP). C/SiC with different ratio of component was prepared.The result shows that the coefficient of thermal expanding(CET) of C/SiC composites was improved with the increasing of SiC content in composites.The matching between C/SiC composites and CVD SiC was improved simultaneously.Through preparing the gradual layer by ways of chemical vapor infiltration(CVI),CVD SiC with density near 100% can be prepared.

The effect of the pre-treatment of bond coat on the cyclic oxidation of EB-PVD TBCs

XU Qiangang, TANG Jianxin, WANG Ning, LU Feng, WU Xueren

2004, 24(4): 30-34.

[Abstract](1419) [PDF 268KB](277)

Abstract:
The thermal cyclic oxidation behavior of a thermal barrier coatings, which is composed of a Ni3Al-based superalloy substrate, NiCoCrAlYHf bond coat prepared by cathode vacuum arc deposition and Y2O3-ZrO2 coating prepared by EB-PVD, was studied between 1150℃ and 30℃. On the basis of the measured interfacial toughness and investigation on the oxidation behavior of TBCs, the effect of the pre-treatment(shot peening and grit blast) of bond coat on the life of TBCs was analyzed. Shot peening and grit blast of bond coat, which decreased the interfacial toughness of TBCs and accelerated the growth of thermally grown oxide(TGO),were not benificial to improve the life of TBCs.

Effects of soft buffer layer on the mechanical properties of T300/BADCy composite

REN Penggang, LIANG Guozheng, YANG Jieying, WANG Jieliang, FANG Hongqiang, ZHANG Zengping

2004, 24(4): 35-38.

[Abstract](1424) [PDF 550KB](245)

Abstract:
The surface of T300 fiber was treated by epoxy resin E51-acton solution to improve the interface properties of the T300/BADCy composites. A soft buffer layer of oxazolidinone was formed on the surface of T300 fiber as the BADCy resin reacted with the epoxy resin coating there. The mechanism of the reaction between BADCy resin and epoxy resin was studied by FTIR. Influences on the mechanical properties of T300/BADCy composite by treatable solution of different concentration were compared. When the concentration of the treatable solution was 5wt%, inter-laminar shearing strength of T300/BADCy composite could be raised by 16%; the flexural strength was also increased by 4%. When the concentration of the treatable solution was 5wt%, the ILSS and flexural strength of T300/BADCy was descended. The shearing fracture images of T300/BADCy composite with or without treated by epoxy resin E51-acton solution were studied by SEM. It was found that there were some cracks and gaps in the interface of untreated T300/BADCy composite,few cracks and gaps exist in the treated T300/BADCy composite fracture, and the break was mainly occurred inside the resins.

Studies on crystallization behaviour of rapidly solidified Al-Ni-Cu-Nd metallic glass and structural characteristics of aluminium based amorphous composites with nanocrystal phase

XIAO Yude, LI Wenxian, MA Zhengqing

2004, 24(4): 39-44.

[Abstract](1444) [PDF 333KB](357)

Abstract:
Rapidly solidified Al87Ni7Cu3Nd3 metallic glass ribbons were prepared by using melt spinning, and were annealed under both continuous heating and isothermal heating regime. The amorphous ribbons and the annealed samples were examined by means of differential scanning calorimetry, conventional X-ray diffraction, and high resolution transmission electron microscopy with selected-(area) electron diffraction, with special interest in primary crystallization into α-Al nanocrystalline particles, in order to understand structural characteristics of the aluminium based amorphous composites with nanocrystal particles. The results show that, the as-spun ribbons are fully amorphous in the micron scale. The metallic glass ribbons devitrify via two main stages: primary crystallization, resulting in α-Al crystal particles precipitation from the amorphous matrix, and secondary crystallization, corresponding to some inter-metallic phases appearing, including Al3Ni, Al11Nd3, and Al8Cu2Nd. The rate-controlling process of the primary crystallization is self-diffusion of Al atoms and the secondary crystallization is limited by bulk diffusion of the Ni,Nd and Cu solute atoms. The ribbons annealed isothermally at the temperature of 90～160℃ consist of two-phase mixture of the α-Al crystal phase and the residual amorphous phase. The primary crystallization will occur at an increasing rate with isothermal temperature improving, and the α-Al crystal relative amount will increase with annealing time prolonging. The typical microstructures of the annealed ribbons exposed isothermally at 110℃ for 130 minutes can be characterized as, high volume fraction(20%) of α-Al crystal nanometer(10nm) particles disperse uniformly in an amorphous matrix.

Study on high-temperature and moist resistant properties of glass fiber/methylsilicone composites

GUO Xu, HUANG Yudong, CAO Hailin

2004, 24(4): 45-48.

[Abstract](1439) [PDF 902KB](377)

Abstract:
The interlaminar shear strength(ILSS) under high temperature and moist resistance of glass fiber/methylsilicone(GF/methylsilicone )composites were investigated. The results show that the ILSS gradually decreased with increase of ignition temperature between room temperature to 800℃, but it is constant during 800～1000℃. The structure of methylsilicone resin at different temperature was characterized by IR spectrum. It is shown that the structure of methylsilicone resin was stable until 800℃.The thermal stability of methylsilicone was studied by TG, the result shows that it has good heat resistant. Meanwhile the interface structure of the composites at 800℃ was investigated by means of SEM. The moist heat resistance testing shows that the water absorption being only(2.35%) and ILSS decreasing by 21.9% after boiling for 100h.

Molecular dynamics simulation of tensile mechanical properties of nano-single crystal argon

LIU Youhong, LIU Xi, HUANG Haiming, XUE Mingde

2004, 24(4): 49-53,62.

[Abstract](1526) [PDF 327KB](343)

Abstract:
Single-crystal FCC cubic argon at nanolevel at two different constant rates of uniaxial tensile loading(2.16m/s, 6.49m/s) is studied by molecular dynamics(MD) using L-J(12-6) inter atomic potential. Deformation and fracture of the work materials duo to voids formation, their coalescence into nanocracks, and subsequent fracture or separation were observed similar to their behavior at macroscale. The true stress-train diagrams obtained by the MD simulation of the tensile specimens show a long slow increase in stress with a gradual increase in strain, and a rapid increase in stress up to a maximum when the value of strain reaches a certain value followed by a sudden drop to negative or a sudden disappear when the specimen fails by brittle fracture. The rate of loading plays an important role in the ultimate strength of the nanomaterials. The ultimate strengths are 2.6GPa and 6.6GPa separately corresponding to the rates of loading 2.16m/s and 6.49m/s. The nanomaterial underwent much more deformation before its sudden rupture than ordinary brittle materials. The brittle rupture form is absolutely different from the ductile rupture form reported previously about ordinary nanomaterials. In addition, the specimens after relaxation were found to be slightly tensile due to internal forces, which is different from the compressed form reported recently for the specimens of FCC materials,such as Al,Cu,Ni,et al, after relaxation.

Thermo-mechanically coupled FEM analysis for drape forming process of fighter plane canopy

YAN Yue, HU Ping, LIU Haipeng

2004, 24(4): 54-56.

[Abstract](1511) [PDF 176KB](216)

Abstract:
As a new forming method of stamping for sheet material, drape forming is now more and more used for solid phase forming process of polymer materials. According to the characteristic of high nonlinearity of large strain deformation, thermo-mechanically coupling and boundary friction involved in drape forming process, this paper established static explicit finite element model based on "continuous equilibrium equation", which is suitable for numerical simulation for problem of this type, and performed FEM analysis for drape forming process of fighter plane canopy made of polymer of polycarbonate(PC).

New trends of research and development of high-performance resin nanocomposites

LU Haijun, LIANG Guozheng, CHEN Xiangbao, ZHANG Baoyan, MA Xiaoyan

2004, 24(4): 57-62.

[Abstract](1467) [PDF 1102KB](233)

Abstract:
The homogeneous dispersion of nano-particles and processing of high-performance polymer nanocomposites still is a technical challenge due to the high active surface of nanoparticles. In this article, the new progress of high-performance resin nanocomposites,including multi-composition, dispersing process of nano-materials, advanced nanocomposites reinforced by fibers and functional nanocomposites are mainly reviewed.

2004 Vol. 24, No. 4