航空材料学报

Investigation of Interrupted Multi-Step Ageing Processes of High Purity Al-Cu-Mg-Ag Alloy

ZHANG Kun, DAI Sheng-long, HUANG Min, YANG Shou-jie, YAN Ming-gao

2007, 27(4): 1-5.

[Abstract](1465) [PDF 655KB](316)

Abstract:
By tensile test,transmission electron microscopy analysis and scanning electron microscopy analysis of fractographs,the effect of multi-step ageing processes on mechanical properties and microstructures of experimental high purity Al-Cu-Mg-Ag type alloy was investigated.The results show that saturated-solution and GP zone contribute to hardening of the experimental alloy which secondly age at ambient temperature or 65℃.The secondary ageing time has little effect on the mechanical properties of the alloy.When the secondary ageing temperature elevate over 100℃,the dominant hardening precipitates will change from θ′ to Ω and with the secondary ageing time properly elongated,the alloy strength will be improved.Compared to T6I6 and T6I4 heat treatment processes,the new interrupted multi-step ageing process,preliminary aged at 185℃ for 20 minutes,water quenched,and finally secondary aged at 150℃ for about 25 to 50 hours,greatly shorten the cycle of the multi-step ageing heat treatment process.Even more,the alloy gains greatly improved ductility and the same tensile yield strength level of that on peak-aged condition.

Influence of Characteristic Inclusion Parameters on Crack Initiation and Propagation in Ultra-High Strength Steel under Tensile Load

FAN Hong-mei, ZENG Yan-ping, WANG Xi-shu, XIE Xi-shan

2007, 27(4): 6-9.

[Abstract](1472) [PDF 615KB](335)

Abstract:
In-situ tensile tests with special designed SEM were conducted to trace the whole process of crack initiation and propagation induced by TiN inclusion in ultra-high strength steel MA250 which is widely used for aircraft engine shafts.Influence of shape and size of inclusion on crack initiation was studied,and the relationship of inclusion area and the initiation stress of the first crack in the inclusion under tensile load was discussed.The results show that the larger is the area of an inclusion,the smaller is the initiation stress of the first crack in the inclusion.

Study on Fatigue Behaviors of ZL114A Alloy

ZHOU Yong-jiang, XIONG Yan-cai, HONG Run-zhou, YAO Wei-bin, ZHANG Zhe

2007, 27(4): 10-13.

[Abstract](1688) [PDF 1152KB](332)

Abstract:
The tensile properties and the fatigue behaviors(axial load,Kt=1,R=-1)of ZL114A alloy was studied.It is indicated that the fatigue properties of ZL114A alloy was equivalent to that of A357 alloy.At the same time,the fatigue damage character of ZL114A alloy was studied.The effect of casting defect such as microporosity and the inclusions in the process of crack initiation,crack propagation and fracture was analyzed.The results indicated that the amount,the dimension and the location of the casting defect had different effect on the fatigue properties of alloy.

Fatigue Property of HVAF Sprayed WC/17Co Coating on 300M Steel

DENG Chun-ming, LIU Min, ZHOU Ke-song, WU Chao-qun

2007, 27(4): 14-18.

[Abstract](1555) [PDF 478KB](339)

Abstract:
Inclusion size in the steel produced significant influence on the fatigue performance of ultra-high strength steel.Fatigue fractograph revealed that the crack was mainly initiated at the inclusion for bare 300M steel and was completely initiated at the inclusion in the substrate for HVAF sprayed WC/17Co coating in 300M steel.The crack was composed of Al2O3.xCaO.ySiO2.Therefore,statistic extreme values and generalized Pareto distribution were used to estimate the maximum inclusion sizes for different mass of 300M steel in comparison with the experimental result.The fatigue limit was predicted according to the estimated maximum inclusion size in the different mass of 300M steel.HVAF treatment led to the higher residual compressive stress in the subsurface of substrate,which was beneficial to the inhibition of crack initiation and propagation.The results showed that the fatigue lives of 300M steel were increased after HVAF treatment at the low stress level,however,decreased slightly due to the limited effect of compressive stress and negative effect of grit blasting at the high stress level.

Study on Correlation between Parameters of “Single Factor” Constitutive Model and Temperature for 7050 Aviation Aluminum-Alloy

YANG Yong, KE Ying-lin, DONG Hui-yue

2007, 27(4): 19-24.

[Abstract](1227) [PDF 1791KB](473)

Abstract:
To investigate the correlation between parameters of "single factor" constitutive model and temperature for 7050 aviation aluminum-alloy,theoretic analyses and material experiments were employed.Based on dislocation theory and material functional relations,an analysis shows that material model is deeply affected by temperature.The quasi-static compression experiments and high-speed impact compression experiments were conducted in order to study the static and dynamic mechanics performance.By the least squares best fit to the available experimental data,material parameters were found.Analyses of experimental curves and comparison of material parameters show that parameters of the "single factor" constitutive model are temperature dependent.Using the mathematical mapping between material parameters and temperature,"single factor" constitutive model for 7050 aviation aluminum-alloy was established,which was proven to be correct by comparing with experimental measurements.The work of this paper provides a useful insight for understanding the material constitutive model and helps to develop further finite element simulation and technology optimization of cutting process for 7050 aviation aluminum-alloy.

Preparing and Study of EB-PVD Thermal Barrier Coatings on Titanium Substrates

HE Bo, LI Fei, ZHOU Hong, YAO Zhen-zhong, SUN Bao-de

2007, 27(4): 25-30.

[Abstract](1596) [PDF 807KB](306)

Abstract:
Two kinds of thermal barrier coatings with NiCoCrAlY bond coatings deposited by electron beam-physical vapor deposition(EB-PVD) and high velocity oxy-fuel thermal spraying(HVOF),respectively,as well as 8wt%Y2O3-ZrO2 ceramic layers deposited in one batch by EB-PVD were prepared on near-α titanium alloys.The field emission scanning electronic microscopy and microhardness indentation were used in comparatively study of microstructures,microhardness of samples. Cracking modes and crack characteristics in TBCs were investigated after thermal cycling in atmosphere,along with the discussion of roles of residual stresses,bonding strengths and mechanical properties of bonding coats in different failure extents.It is found that morphologies of BCs deposited by different methods(EB-PVD and HVOF) resulted in the different microstructures and microhardness of their upper YSZ.The denser and more homogeneous BC prepared by EB-PVD led to the YSZ with slim and dense columnar clusters and higher microhardness,and the inhomogeneous and porous latter resulted in the upper YSZ with coarse and loose bonded columnar grains and lower microhardness,and the TBC with BC deposited by EB-PVD was more protective,which was synthetically induced by residual stresses,bonding strengths and mechanical properties of bonding coats.

Research of Corrosion Behavior for Al-Li Alloy at Different Aged States in Cl-Solution

ZHANG Lei, CHEN Qun-zhi, WANG Yu-ya, YAN Wei-dong

2007, 27(4): 31-35.

[Abstract](1577) [PDF 482KB](293)

Abstract:
Salt spray sulfuration corrosion tests were applied to 1420 Al-Li alloy.Maximum corrosion depth was measured to evaluate the severity of corrosion.Since localized corrosion was a stochastic phenomenon,a statistic analysis method was used to deal with the data.The results showed that,for 1420 alloy at double-ageing state,the maximum corrosion depth was consistent with the Gumbel distribution law.TEM micrographs revealed that δ′ phase and S phase were uniform in the double-ageing state alloy.Thus enhanced the corrosion performance of 1420 alloy.

Silicide Coatings on Niobium Alloys Prepared by Complex Pack Cementation

XIAO Lai-rong, XU Liang-liang, YI Dan-qing, CAI Zhi-gang, WANG Xiao-ning

2007, 27(4): 36-41.

[Abstract](1633) [PDF 982KB](217)

Abstract:
The silicide coatings on C103 niobium alloy were prepared by complex packing cementation.Microstructure of coatings before and after oxidation was analyzed by means of XRD,SEM and EDS.Tie results show that the silicide coatings prepared by pack cementation are formed by reactive diffusion;the coatings are multi structures with MoSi2 as main layer;at the high temperature oxidation circumstance,the dense amorphous glass scale is formed on the silicide coating,which imped the process of the oxygen diffusion to inner layer,thus coatings represent good high-temperature oxidation and thermal shock resistance.

Effects of the Method Adding Ti on the Microstructure of Carbide/Fe Based Alloy Composite Coating Prepared by Reactive Braze

ZHAO Zu-de, XU Zhen-hua, HUANG Ji-hua, WEI Shi-zhong, ZHAO Xing-ke, ZHANG Hua

2007, 27(4): 42-45.

[Abstract](1502) [PDF 871KB](259)

Abstract:
Carbide/Fe based alloy composite coatings with a metallurgical bond to a mild steel substrate,were prepared by reactive braze, using ferrotitanium or titanium,ferrochromium,ferroboron,nickel,silicon,carbon powder as the raw materials in vacuum braze furnace.The influence of the method adding Ti on the microstructure of the coatings was studied.The results showed that the microstructures of the composite coatings were composed of the bounding phase of Fe based solution and the reinforcement phases of titanium carbide and chromium carbide.The method adding Ti had an important effect on the microstructures of the composite coatings.The different methods adding Ti resulted in a great difference in the morphology of titanium carbide,as well as the density of the composite coatings.It is believed that the method adding Ti had the influence on the microstructure of the coatings because the dynamics conditions were different when TiC of the coatings were synthesized.

Effect of Heat Treatment on Mechanical Properties of NiCrAl/Ni₃Al Microlaminates

GUAN Chun-long, XU San-kui, QI Ying

2007, 27(4): 46-49.

[Abstract](1473) [PDF 516KB](220)

Abstract:
NiCrAl/Ni3Al microlaminate composites were fabricated by electron beam physical vapor deposition(EB-PVD).The tensile tests for microlaminate samples under different temperature were performed on the as-deposited and aged state composites.The relationship of aging temperature and tensile properties for laminates was investigated.The results show that brittle rupture occurs along the intergranular of column crystals of as-deposited specimens,while the fractures of annealed specimens are tough fractures.Compared with those of condensates,mechanical properties of microlaminates at room and high temperatures are enhanced by heat-treating at 740℃ for 32h.

Microstructure and Abrasive Wear Resistance of Cr₃C₂/Ni₃Al Composite

GU Guo-rong, LUO He-li, LI Shang-ping, LIU Pei-ying, FENG Di

2007, 27(4): 50-53.

[Abstract](1426) [PDF 623KB](257)

Abstract:
Through welding on the surface of carbon steel, Cr3C2/Ni3Al wear-resistant composite was successfully fabricated by the metal-powder-core wire.The average dimension of reinforcement reduced down to less than 10μm from raw material of 150μm,and the microstructure was homogeneous and stable.The abrasive resistance of the composite was twice as much as the traditional wear-resistant superalloy-Stellite12.Reinforcement of volume and size,the strain-hardening ability of matrix were considered as the main reasons for the composite exhibited good abrasive wear-resistance.

Mechanical Properties of the Composites Fabricated by In Situ Method in AlTiO₂-C System

ZHU He-guo, YUAN Yun-zhan, CHEN Shi, WU Xu, YU Hai-yan

2007, 27(4): 54-59.

[Abstract](1491) [PDF 1612KB](214)

Abstract:
The room and elevated temperature mechanical properties,and fracture mechanism of the composites fabricated by in situ reaction method in the Al-TiO2-C system were studied.The results indicate that when the C/TiO2 mole ratio is zero,the reinforcements of the composites are composed of α-Al2O3 and Al3Ti,the ultimate tensile strength and elongation at room temperature are 250.4MPa and 4.0% respectively.The fracture mechanism of the composite is characterized by crack nuclei initiating and propagating in the some Al3Ti rods and segregation region of the α-Al2O3 in the matrix.When the C/TiO2 mole ratios increases,the amount of Al3Ti phase decreases.When the C/TiO2 mole ratio reaches 1,the Al3Ti phase almost eliminates,the ultimate tensile strength and elongation are promoted to 350.8MPa and 6.0% respectively.There are big ductile dimples around the Al3Ti and some fractured Al3Ti in the tensile cross section surfaces of the composites.With increasing the test temperature,the ultimate tensile strengths decrease and the elongations increase.The bonding strength of the Al3Ti with matrix decreases and the Al3Ti rods are pulled out from the matrix.The crack nuclei initiate and propagate in the interfaces of the Al3Ti rods with matrix are previous to taking place in the matrix.At the test temperature of 727K,the tensile strength and elongation of the composites with C/TiO2 mole ratio of 1.0 are 93.3MPa and 11.0% respectively.

Thermophysical Properties of 2.5D C/SiC Composites

LI Hong, XU Yong-dong, ZHANG Li-tong, CHENG Lai-fei, MA Jun-qiang, ZHANG Qing, LI Kai-yuan

2007, 27(4): 60-64.

[Abstract](1552) [PDF 504KB](482)

Abstract:
The coefficients of thermal expansion and thermal diffusivity of the 2.5D carbon/silicon carbide composites tested from room temperature to 1400℃ by the thermal dilatometer and laser flash apparatus.The results showed that the coefficient of thermal expansion increased slowly as temperature increased,with fluctuations at 350℃ and 700℃,and the transverse coefficient was slightly higher than the longitudinal coefficient.However,the coefficient of thermal diffusivity decreased as temperature increased,and the rate of decline turned slower.The coefficient of thermal diffusivity of the composite with SiC coating increased by 1~2 times compared to the material without SiC coating.

Predict the Mechanical Properties of Advanced Stiffened Grid Composite Structure

JIANG Shi-cai, XING Li-ying, LI Bin-tai, CHEN Xiang-bao

2007, 27(4): 65-68.

[Abstract](1528) [PDF 502KB](311)

Abstract:
The mechanical properties of the advanced stiffened grid structure was predicted through MSC.Nastran.The AGS,panel and rib were stimulated through shell cell.Load/displacement curve of the AGS 0° tensile/bend properties show that the AGS have the excellent mechanical properties.The AGS 0° tensile/bend properties decrease with the height of the AGS increasing for the rib contributing factor increasing in the total AGS mechanical properties.

Influence of Fabric Structure on Antidamnification of SiC Matrix Composites

ZHOU Chang-cheng, ZHANG Chang-rui, HU Hai-feng, ZHANG Yu-di, WANG Zhi-yi

2007, 27(4): 69-72.

[Abstract](1398) [PDF 404KB](198)

Abstract:
The effect of damnification of different structural fabric on microstructure of Cf/SiC composites were investigated,and the results were analyzed thoroughly from the point of view of textile technics. The results show that 2.5D fabric structural composites is superior to other three fabric structural composites remarkably on condition that the fabric structure were damnified slightly.And the other three fabric were destroyed entirely at a low stress.

Synthesis of a Novel Hybrid Sizing and the Effects on Properties of Carbon Fiber/Isomeric Polyimide Composites

ZHANG Chun-hong, ZHANG Mi-lin, CAO Hai-lin, ZHANG Zhi-qian, GAO Lian-xun, WANG Zhen

2007, 27(4): 73-79.

[Abstract](1532) [PDF 1324KB](248)

Abstract:
A novel modifier,γ-(phenylethynyl)imidepropyltriethoxysilane(PEIPTES) was synthesized to make modified SiO2 precursor,and then the novel isomeric polyimide/SiO2 hybrid sizing was prepared.The structure and properties of PEIPTES,the structure of novel hybrid sizing were characterized by element analysis,FT-IR and thermoanalysis.The results indicated chemical bond was produced between organic phase and inorganic phase in the sizing.Analysis by AFM illustrated that a layer with nano particles was formed on carbon fiber surface after treated by the novel hybrid sizing,roughness was increased and interface properties of composites would be improved.It was confirmed that the hybrid sizing increased ILSS of the carbon fiber/isomeric polyimide composites,the optimal content of SiO2 was 5wt%.At the same time impact properties and thermal properties of the composites were both increased obviously.

Development in Double-Properties Turbine Disk of P/M Superalloy

HU Ben-fu, TIAN Gao-feng, JIA Cheng-chang, LIU Guo-quan

2007, 27(4): 80-84.

[Abstract](1851) [PDF 803KB](829)

Abstract:
P/M superalloys become first-choice material for high performance applications such as turbine disks used for high thrust-weight ratio aeroengine due to the superior high temperature porperties.In recent years,because of the in-depth research on double-properties turbine disk with duplex structure,the prospect in application of P/M superalloy will be more hopeful.The development of double-properties turbine disk applied in domestic and abroad aircraft was summarized,the encounter problems in the study were analysed with emphasis,some suggestions for improvement on double-properties turbine disk were also proposed.

2007 Vol. 27, No. 4