航空材料学报

Microstructure Evolution of Cu-1.0% Cr Hypoeutectic Alloy During Directional Solidification

LI Xiao-li, LI Jin-shan, HU Rui, KOU Hong-chao, FU Heng-zhi

2008, 28(5): 1-5.

[Abstract](1435) [PDF 593KB](170)

Abstract:
Directionally solidified microstructures were investigated based on the calculation and comparison of interface growth temperatures of different phases in Cu-1.0% Cr hypoeutectic alloy at various growth velocities.The results show that the entirely coupled eutectics could not be obtained at the growth rate higher than 5μm/s and the α-Cu phase will be the primary phase solidified ahead of the coupled eutectics,which agrees with the experiment results.In addition,the primary dendritic arm spacing,dendritic radius of α-Cu phase and the volume fraction of eutectics decrease with the increase of the growth rate.The value of primary dendritic arm spacing of Cu-1.0% Cr alloy measured in the experiment is very close to the calculation results of KF model.

Effect of V and Al on Oxidation Resistance of Nb-Si Based Ultrahigh Temperature Structural Materials

KANG Yong-wang, QU Shi-yu, SONG Jin-xia, HAN Ya-fang

2008, 28(5): 6-10.

[Abstract](1631) [PDF 846KB](263)

Abstract:
The Nb-Ti-Si and Nb-Ti-Si-V-Al alloys were prepared by non-consumable arc melting method.The as-cast microstructure and oxidation behavior of all alloys at 1250℃ were investigated.The results showed that the V and Al promoted the reaction Nb3Si→Nbss+Nb5Si3,which transformed the phase components from Nbss+Nb3Si to Nbss+Nb5Si3 and increased the volume fraction of Nbss phase.And the oxidation resistance of Nb-Si based alloy was improved with the increment of V and Al addition.The SEM analysis of oxide scale showed that the addition of V and Al modified the loose microstructure of oxide scales to more compactable structure,which may reduce the oxidation rate.In addition,the V and Al decrease the weight of spalt oxide scale and the lost thickness of metal.After 1250℃/50h oxidation,the lost thickness of Nb-21.9Ti-11.9Si-4.4V-4.1Al alloy was only 0.1mm.

Microstructure and Properties of 2Cr16Ni2MoN Stainless Steel

ZHONG Ping, SU Bin, WANG Jun-li

2008, 28(5): 11-16.

[Abstract](1434) [PDF 1048KB](180)

Abstract:
The effect of heat treatment on microstructure and mechanical properties of aged hardening stainless steel 2Cr16Ni2MoN were examined by means of tensile test,impact test,hardness test,transmission electron microscope and scanning electron microscope.The results show that there are undissolved(Cr,Mo)23C6 carbides in steel when the lower solution treated temperature is used.Increasing the solution treated temperature results in coarsening of the packet and block structure of the lath martensite.The optimum solution treated temperature is 1040℃.The aged hardening is caused by the precipitation of extremely fine(Cr,Fe,Mo)2C carbides which are coherent with matrix.The steel aged at 560℃ has high strength and good impact toughness,which is attributed to the formation of fine M2C in the lath,a mixture of lath martensite with high density dislocations.

Effect of Type and Morphology of Inclusions on Plastic Properties of Ultrahigh Strength Steel

XIA Zhi-xin, YANG Zhuo-yue, SU Jie, DING Ya-ling

2008, 28(5): 17-21.

[Abstract](1599) [PDF 1210KB](418)

Abstract:
The type and size distribution of inclusion on G50 steel smelted by different metallurgy processes have been analyzed by SEM,EDAX.Results have indicated that tensile and yield strength are mainly affected by microstructure regardless of type and morphology of inclusions.Cohesion between NbCN and matrix is much bigger than that of between MnS and matrix.During plastic fracture,crack propagation is manipulated by the mechanism of competition in the inclusion of different type and morphology.It firstly appears in the site of inclusions which have both the poor cohesion with matrix and the shape of stress concentration,then at the inclusions with strong cohesion with matrix and stress concentration.

Research on Hot Compression Deformation of Ni-Copper Alloy with high content of Si

YU Yang, ZHOU Cheng, LIU Gao-yuan, TAO Chun-hu, LIU De-lin

2008, 28(5): 22-26.

[Abstract](1467) [PDF 705KB](182)

Abstract:
Hot compression deformati on simulation of Ni-Copper alloy was investigated on Gleeble-1500 hot simulation at different deformation temperatures(fromT1toT4) and various strain rates(S1,S2,S3,S4,andS5).The microstructure of the Ni-Copper alloy after deformation was also studied.The relationship between flow stress and deformation temperature were analyzed,and the deformation activation energy and stress exponent were calculated.The results show that the peak flow stress becomes larger with the strain rate increasing at the same temperature,and gets smaller with the deformation temperature increasing at the same strain rate.The Ni-Copper alloy has dynamic recrystallized crystal in the condition of high temperature deformation.

Formability and Numerical Simulation for as-quenched Aluminum Alloy Sheet

GAO Hong-zhi, ZHOU Xian-bin

2008, 28(5): 27-31.

[Abstract](1534) [PDF 1052KB](334)

Abstract:
The influence of heat treatment on formability of aluminum alloy sheet could not be ignored and the fact that formability of as-quenched aluminum alloy sheet is not well understood has obstructed the improvement of forming process and the application of numerical simulation.Based on the practical forming process of 2D12 aluminum alloy,some experiments were conducted to investigate the influence of pre-stretching before heat treatment and age hardening time on the behavior and formability of 2D12 aluminum alloy after pre-stretching and solution heat treatment.The experiments indicate that as-quenched aluminum alloy sheet has good formability and the formability is worsened with the increase of pre-stretching and age hardening time.Based on the experiment,numerical simulation of sheet metal forming for as-quenched and annealed aluminum alloy is conducted.The results indicate the sheet forming need greater force and energy in as-quenched condition than in annealed condition and there is more residual stress and spring back in as-quenched condition.With the increase of aging hardening time and pre-stretching,the forming force,spring back and reduction of thickness grows and the thickness uniformity becomes bad.

Influence of Hydrogenation on Physical and Pressing Properties of TC21 Alloy Powder

TIAN Ya-qiang, CHEN Xiao-hui, HOU Hong-liang, REN Xue-ping

2008, 28(5): 32-36.

[Abstract](1466) [PDF 847KB](265)

Abstract:
The influence of hydrogenation on the particle morphology and surface state,particle microstructure and phase component,microhardness and pressing property of TC21 alloy powder were investigated by means of SEM,powder inlaid,XRD and die forming.The results show that the hydrogenated TC21 alloy powder with different hydrogen content possess irregular morphologies,and which are composed of bright α phase and dark β phase and exhibit lamellar structure,α/β cluster and basket structure.With the increase of hydrogen content,the microhardness of hydrogenated TC21 alloy powder shows a decreasing trend,the α phase decrease and the β phase increase gradually,a little amount of α″ phase is formed.The compressive property and forming property of hydrogenated TC21 alloy powder get worse firstly and then get better gradually,but the change of compressive property is not obviously.The pressing properties of hydrogenated TC21 alloy powder with hydrogen content of 0.10 wt%,0.39 wt% are better than that of others and the powder with hydrogen content of 0.22 wt% is the worst one.

Effect of Y₂O₃ Doped on Micro-Structures and Properties of In-Situ TiB/TiAl Composites

LI Yun-ming, WANG Fen, LIU Yuan, ZHU Jian-feng

2008, 28(5): 37-40.

[Abstract](1529) [PDF 301KB](196)

Abstract:
TiB/TiAl composites doped Y2O3 was fabricated.The effect of rare-earth doping on the microstructures and properties was analyzed by XRD,SEM and universal properties tests.The refinement mechanism of rare-earth oxide was investigated as well.The results showed the phases of the composites were composed of the matrix of Ti3Al and TiAl phase,the reinforcement of TiB phase,a small amount of Al2O3 and YAl3(BO3)4 phase.The YAl3(BO3)4 for ceramics was diffused into matrix minimally、homogeneously,which can refine grains.The Y2O3 doped which impacted the material structure of TiB/TiAl composites and changed the content of the TiAl and Ti3Al phase,and improved mechanical properties of composites effectively.

Experimental Research on Microcosmic Mechanism of Stress-Magnetic Effect for Magnetic Memory Testing

REN Ji-lin, CHEN Chen, LIU Chang-kui, CHEN Xi, SHU Ming-hang, CHEN Xing

2008, 28(5): 41-44.

[Abstract](1460) [PDF 831KB](340)

Abstract:
Influenced by the earth magnetic field,the irreversible reorientation of domain organization with the characteristic of magnetostriction will be occurred in internal organization of the loaded ferromagnetic material.The different compressed loads are exerted onto the 20 steel and 40 steel specimens which are annealed,then make them into the metallographic observation test specimens,and observe the magnetic domain structure by the Bitter Method.Then contrast the magnetic domain structures of different specimens and analyze different affections of different loads.The experimental results shows that when without stress or with less stress,the lamellar domains appears on the area,and the domain walls are parallel in the same crystalline grain.The labyrinthian domains appear accompany with the concentrated stress enhancing,and the harder stress loads the more labyrinthian domains appear.Moreover,the length and the space between of the domain walls change accordingly.

Effect of Material Properties on Reasonable Indentation Depth of TBCs

QIAN Xiu-qing, ZHANG Jian-yu, FEI Bin-jun

2008, 28(5): 45-49.

[Abstract](1441) [PDF 1747KB](320)

Abstract:
The reasonable indentation depth of the thermal barrier coating system is investigated using a combination of dimensional analysis and finite element analysis.Scaling functions relating the reasonable indentation depth are given according to the dimensional analysis.Based on the method of exacting the material properties of elastic-perfectly plastic material using the sharp indenter,the method to determine the ratio of the reasonable indentation depth to coating thickness below which the substrate material has a negligible effect on the indentation response of the coated system is proposed.Finally,the effect factors of reasonable indentation depth to coating thickness ratio are studied.The results reveal that the effect of the elastic modulus of substrate on the reasonable indentation depth is biggest,and effect of the material properties of bond coat is bigger,while the effects of material properties of the thermally grow oxide and the yield stress of substrate are small.

Influencing Factors of Rate and Surface Quality of Corrosion Processing for TC4

LIN Cui, LIU Feng, ZHAO Qing, WEN Qing-jie, DU Nan

2008, 28(5): 50-54.

[Abstract](1597) [PDF 667KB](415)

Abstract:
In this paper,the influence of ingredients in corrosion solution and process parameters on corrosion rate,surface roughness and surface evenness for TC4 titanium alloy was discussed.Surface morphology was investigated by scanning electron microscopy before and after corrosion processing.The results show that HF concentration and solution temperature directly determined corrosion rate.The corrosion rate was promoted with increasing HF concentration and temperature.HNO3 can significantly reduce surface roughness.The titaniumions had the impact on corrosion rate and evenness to some degree.In solution with low titanium ions content,high corrosion rate,low surface evenness can be observed.When titanium ions content increased,corrosion rate slowed down,meanwhile surface unevenness increased.Time turnover and agitating can enhance evenness for vertical hanging specimen.

Finite Element Simulation of Multi-Pass Equal Channel Angular Extrusion of Elastic-Plastic Material with Strain Hardening

LEI Li-ming, HUANG Xu, DUAN Rui, CAO Chun-xiao

2008, 28(5): 55-58.

[Abstract](1546) [PDF 511KB](191)

Abstract:
The deformation behavior of multi-pass(up to four passes) equal channel angular extrusion of elastic-plastic material with strain hardening was investigated by Finite element simulation.The results show that the size and symmetry of the plastic deformation zone increase and the corner gaps decrease when ECAE pass is increased.With the increase of ECAE pass via route A,the homogeneity in equivalent plastic strain decrease and the largest plastic strain zone moves towards the front-top part of the specimen.However,increasing the ECAE pass via route C results in more uniform equivalent plastic strain and the largest strain zone occurs in the middle of the specimen.The maximum value of cumulative plastic strain in route C is smaller than that in route A with the same processing passes.

Numerical Simulation of Welding Distortions of Aluminum Alloy under Pretension Stresses

LI Jing-yong, LIU Zhi-peng, WANG Hu, LU Ya-ming

2008, 28(5): 59-63.

[Abstract](1515) [PDF 608KB](217)

Abstract:
The temperature and stress fields,which appeared during welding of aluminum alloy sheet under different pre-tension stresses,are numerically simulated by using ANSYS finite element analysis software and programming with APDL language.The calculation results show that pre-tension welding method can reduce the welding residual stresses effectively,and the longitudinal and transverse residual stress decrease gradually with the pre-tension stress increasing.When pre-tension stress σp changes from 0 to 90%σ0.2,the residual stress reduced by 85.6%.The simulated results are well consistent with the experimental ones.

Study on Thermal Stability and Interfacial Structure of YAl₂/MgLial Composites

WANG Su-jie, WU Guo-qing, ZHANG Tao, HUANG Zheng

2008, 28(5): 64-67.

[Abstract](1528) [PDF 721KB](196)

Abstract:
The thermal stability of YAL2p/MgLiAl composites was studied by XRD,TEM,HREM and material tensile teat.The results show that,there are no detectable products on the interface after fabrication or subsequent heat treatment,and the interface between YAl2 and MgLiAl alloy is not weakened after the heat treatment.The tensile strength and elongation of the composite after being solution treated at 350℃ for 10h exceed those of the as-cast composite 11% and 20%,respectively.The Gibbs free energy was calculated to assess the thermodynamics driving force for the reaction of YAL2 and MgLiAl matrix.

Influence of Refractory Compounds Introduction on Oxidation Resistant Performance of 2D C/SiC Composites via Precursor Infiltration and Pyrolysis

WANG Qi-kun, CHEN Zhao-hui, HU Hai-feng, ZHANG Yu-di

2008, 28(5): 68-72.

[Abstract](1499) [PDF 511KB](249)

Abstract:
Three composites of 2D C/SiC-ZrB2(TaC,ZrC) were prepared via introducing of refractory compounds(ZrB2,TaC,ZrC) into 2D C/SiC composites,and the influences upon mechanical,oxidation resistant performance and microstructures of 2D C/SiC composites were investigated.The results showed that the introduction of ZrB2 and TaC significantly increased the oxidation resistance performance of 2D C/SiC,while the introduction of ZrC decreased the oxidation resistance performance.The improved oxidation resistance performance of 2D C/SiC composites was attributed to the formation of surface protection films of viscous ZrO2,B2O3 and Ta2O5 derived from the oxidation of ZrB2 and TaC,which prevented oxygen diffusion into the composites.

Microstructure and Mechanical Properties of a Three-phase Alumina-zirconia-Spinel Nanocomposite Ceramic

CHEN Guo-qing, XIE Jie, WANG Xu-dong, DONG Hong-gang, HOU Xiao-duo

2008, 28(5): 73-77.

[Abstract](1605) [PDF 1262KB](239)

Abstract:
Alumina-30mol%zirconia-30mol%spinel(AZ30S30) nanocomposite powders were synthesized by using sol-gel method.A three-phase alumina-zirconia-spinel nanocomposite ceramic was prepared by using hot-pressing sintering.The microstructure observation demonstrates that as-sintered ceramic is a typical inter/intra granular nano-structured composite.Both the matrix alumina grains and the second phase grains are equiaxed.The inter-granular zirconia grains and spinel grains are uniformly distributed in alumina matrix.There are also many small zirconia particles,trapped within alumina grains,which formed intra-granular phases.The fracture toughness measurement and indentation tests demonstrate that the maximum microhardness of as-sintered nano-structured ceramics is 35 GPa,much higher than 22 GPa in the micro-sized ceramics.The results demonstrate that the microhardness increases with the decrease of the grain size in as-sintered ceramic composite.On the other hand,the fracture toughness of micro-sized composite ceramic is 8.9 MPa m1/2,while that of nano-structured ceramic is 10.04 MPa m1/2.The main toughening mechanism in as-sintered nanocomposite ceramics is phase transformation toughening of zirconia,intra-granular nano-phase toughening and grain refining toughening.

Surface Functionalization of Carbon Nanotubes Grafted from Epoxy-Terminated Molecule

ZHANG Jiao-xia, ZHENG Ya-ping, YANG Xiao-dong, NING Rong-chang, CHEN Li-xin

2008, 28(5): 78-82.

[Abstract](1546) [PDF 1295KB](417)

Abstract:
Epoxy resin was grafted on the acidified Multi-carbon nanotubes(MWNTs) by covalent modification method.The changes in chemical and physical structure were investigated by FTIR,Raman spectra,TGA and TEM.As a result,when MWNTs were modified with strong acid,the carboxyl and hydroxyl groups were found on the surface of MWNTs.The epoxy groups had covalently grafted onto the surface of MWNTs and epoxy resin content on MWNTs surface was about 39%.The curing behaviors of MWNTs/epoxy nanocomposites were examined by differential scanning calorimetry(DSC) technique.The modified MWNTs evidently affected the curing reaction of matrix composites.

Condensed Structures and AC Electrical Properties of Polyetheretherketone/Multi-Walled Carbon Nanotubes Composites

YAN Wen-juan, ZHAN Mao-sheng, WANG Kai

2008, 28(5): 83-88.

[Abstract](1496) [PDF 1545KB](232)

Abstract:
Polyetheretherketone(PEEK)/multi-walled carbon nanotubes(MWNTs) composites with different mass ratios were prepared by solid alloying;the condensed structures were observed by field emission scanning electron microscope;melt endothermic peaks,melt enthalpy and AC electrical properties of two kinds of composites prepared by slow cooling and rapid cooling were compared.The results showed that MWNT could be cut short and dispersed well in PEEK matrix by solid alloying,which was benefit to form condensed;the formation of low temperature crystal phase increased with the addition of MWNT;the melting peak of low temperature crystal phase became more significant with MWNT content increasing;the rapid cooling process decreased the crystallinity and broadened the crystal size distribution,which made conductive network of MWNT with different lengths formed between crystals with different sizes,so the resistance and percolation threshold decreased;the AC electrical property parameters of PEEK/MWNT composites changed with frequency and MWNT content regularly,but there were different critical frequencies and percolation thresholds in the composites prepared by different cooling rates.

Effects of SiC with Different Sizes on Properties of Fluoroether Rubber

JIANG Hong-gang, WANG Li, LI Fu-ping, ZHU Li-ping

2008, 28(5): 89-93.

[Abstract](1498) [PDF 1113KB](301)

Abstract:
Effects of different sizes of SiC on the mechanical,thermal conductive,friction and abrasion properties of fluoroether rubber were studied.Results showed that both the modulus at 100% elongation and tensile strength of the vulcanized rubber increase with the decrease of particle sizes.The rubber filled with 15%(in volume) 20nm SiC behaves outstanding mechanical properties.The thermal conductivity of fluoroether rubber filled with larger size of SiC particles is greater than that filled with smaller size of SiC due to the lower interfacial thermal resistance.The thermal conductive coefficient of the rubber can be also enhanced by filling different sizes of SiC in a certain ratio.The friction and abrasion properties of the rubber filled with SiC whisker can be dramatically improved.

Study on the Solution Properties of PBO/MSA

LIN Heng, CHENG Jian-jun, LIU Zi-tao, ZHUANG Qi-xin, HAN Zhe-wen

2008, 28(5): 94-99.

[Abstract](1617) [PDF 362KB](239)

Abstract:
The property of PBO/MSA solution was studied by using Ubbelohde viscometer.The effect of the solution consentration on the viscosity was analyzed by diluted extrapolation method.The results showed that the PBO chain conglomerate in the solution with low concentration.And there is a"polyelectrolyte effect"in PBO/MSA solution with an infinite diluted concentration.The effect of the [η] of PBO on its molecular weight was also investigated.The results revealed that the third-order polynomial based on the semi-rigid polyelectrolyte model is better than the Mark-Houwink equation in terms of the rigid rod-like model in relating the [η] and Mw of PBO.

Digital Visible Spectrum Analysis of Mo in Ni-based Alloy

LIU Ping, YANG Jun-hong

2008, 28(5): 100-102.

[Abstract](1373) [PDF 351KB](211)

Abstract:
The visible spectrum of molybdenum was studied in Ni-based alloy by digital automatic analysis system.The researches were carried on the character of Mo550.65nm and Mo588.83nm line groups in Ni-based alloy.The digital analysis method was developed for visible spectrum of molybdenum in Ni-based alloy.The results can meet the qualitative analysis and the quantitative analysis on molybdenum in Ni-based alloy,which also can be used to exactly examine alloy and avoid the commixing of material on spot.

Behaviour and Analysis of Creep Damage of Duralumin Alloy 2A12

WANG Xiang-sheng, ZHAO Bin, FENG Zhen-zhou

2008, 28(5): 103-106.

[Abstract](1552) [PDF 1038KB](431)

Abstract:
The creep-damage parameters,localization of damage and the damage degree were obtained through the uniaxial tension creep test with duralumin alloy 2A12 in the condition of constant temperature(210℃) and different loads.The finite element model was established on a plate creep specimen.The variation of creep strain with time and the evolution of creep damage at 210℃ under constant load were analyzed using FEM incorporated with modified K-R creep damage constitutive equations.The result of numerical simulation was accord with conventional creep tests.The result also showed that the creep damage at the central part was high,and localization of damage was obvious.

2008 Vol. 28, No. 5