航空材料学报

Study on Modification and Mechanism of Titanium Alloy by Die Forming and Sintering Utilizing Hydrogenated Powder

TIAN Ya-qiang, HOU Hong-liang, REN Xue-ping

2011, 31(3): 1-7.

[Abstract](1251) [PDF 1555KB](212)

Abstract:
The effect of hydrogenation on structure and properties of TC4 alloy sintered body was researched by means of the room-temperature die forming and sintering in protection air using hydrogenated powder.A new progress for preparation of Ti alloy parts the by the combination of hydrogenation titanium alloy powder forming and thermohydrogen treatment for titanium alloy was put forward.The results showed that with the increase of hydrogen content and increasing of sintering temperature,the density of TC4 sintered body had a rise trend gradually,the microstructure was changed from widmanstaten to two-state transitional structure,the lamellar and needle-like microstructure got thinner,and more fine isometric grains appeared.After annealing,the microstructure of TC4 sintered body with safe hydrogen content got more uniformity and refinement,the compressive yield strength showed an increasing trend.As a conlusion,the hydrogen content of 0.42 wt% was the best for the TC4 alloy sintered body according to the density and mechanical property.

Structure and Hot Deformation Behavior of ESR-CDS René88DT

FU Rui, CHEN Xi-chun, REN Hao, FENG Di

2011, 31(3): 8-13.

[Abstract](1453) [PDF 1499KB](227)

Abstract:
Electroslag remelting continuous directional solidification(ESR-CDS) technology was been developed in CISRI,it was a purity and free of solidification macro-defects remelting technology in industrial scale.René88DT superalloy ingot(Ø150mm) was successfully produced by ESR-CDS.The columnar grain is grown parallel with the solidification direction along at 100 crystallographic orientation.Compared with the conventional ESR ingot,the ESR-CDS René88DT alloy ingot has finer pinetree structure,lower element segregation degree.The size of the dispersed granular carbides precipitated in grain boundary is smaller.The uniform complete dynamically recrystallized structure is achieved from the isothermal compression tests samples of ESR-CDS ingot under the condition of 1100℃,70% strain quantity and strain rate from 0.05s-1 to 0.1s-1.Isothermal forging was used to produce Ø170×73 pan billets with a 70% strain quantity.The dynamically recrystallized structure(uniform grain size 50μm) was generated in the billet except the deformed dead zones at top and bottom.

Microstructure Evolution of ZK60 Magnesium Alloy during Homogenization

HE Yun-bin, PAN Qing-lin, LIU Xiao-yan, LI Wen-bin

2011, 31(3): 14-20.

[Abstract](1446) [PDF 2318KB](214)

Abstract:
The microstructure evolution and composition distribution of as-cast and homogenized ZK60 magnesium alloy were investigated by optical microscope,scanning electron microscope,energy dispersive X-ray diffraction and X-ray diffraction.The results show that serious dendrite segregation is existed in the ZK60 alloy ingot,a number of non-equilibrium eutectic phases which mainly contain α-Mg and Mg3Zn7 are segregated at the grain boundaries and between dendrites boundaries.The non-equilibrium eutectic phases are dissolved gradually with the increasing temperature and holding time after the homogenization process,and the dendrite segregation is eliminated.However,the alloy is over-burnt when the temperature is over 420℃.The optimal homogenization regime is suggested to be 400℃/12h,which is basically consistent with the result obtained by homogenizing kinetics equation.

Effect of P on Microstructure and Mechanical Properties of NiAl-34Cr Alloy

QI Yi-hui, LI Hui, YANG Xu-guang, GUO Jian-ting

2011, 31(3): 21-25.

[Abstract](1293) [PDF 1150KB](199)

Abstract:
The alloy ingots of NiAl-34Cr-xP with the P content(0.005%,0.02%,0.05%,0.15%,phase(mass fraction)) were melted by a non-consumable vacuum electric-arc furnace.The microstructures of alloys are all composed of NiAl phase and Cr phase,and are the typical cellular dendrite crystals.The size of the cellular colony is reduced gradually with the increasing of P content.Also the Cr3P phase is existed in the NiAl-34Cr-0.05%P and NiAl-34Cr-0.15%P alloys.The size of the cellular colony is increased slightly by comparison with the identical P content alloy after heat treatment.The hardness of the heat treated alloy is lower than that of the cast alloy,and the more temperature of treatment,the lower the hardness is.The reason is that the high temperature treatment causes the Cr phase accumulative coarsening and the increment of the size of cellular colony.

Effect of Adding Rare Earth Sm and Cu on Supersaturated Ag90Ni10 Alloy Induced by Mechanical Alloying

WU Wan-yan, WANG Wen-fang, LIU Liang, WU Yu-cheng

2011, 31(3): 26-30.

[Abstract](1510) [PDF 1246KB](219)

Abstract:
The X-ray diffraction(XRD),scanning electron microscope(SEM) and transmission electron microscope(TEM) were used to analyze the formation of supersaturated Ag90Ni10 phase and the effect of adding rare earth Sm and alloy element Cu on the mechanical alloying process.The change of the lattice parameters and grain size for all the supersaturated powders after annealed were also measured.Then the microstructure,density,hardness and resistivity of the samples were measured after being prepared by the method of powder metallurgy.The results of the precise determination of the lattice parameters by XRD showed that after mechanical alloying for 60 hours,the nanocrystalline Ag-Ni powders were obtained and the maximum solid solubility of Ni in Ag was reached 2.87at%.Both the rare earth Sm and alloy element Cu could accelerate the mechanical alloying process,reduce the ultimate grain size of powders,especially the Sm.The alloy element of Cu could improve the density,hardness and conductivity of the alloy.

Effect of Sc Addition on Deformation Behavior of Mg-3Li Alloy at High Strain Rates

SHA Gui-ying, SUN Xiao-guang, LIU Teng, ZHU Yu-hong, FENG Xiao-gang

2011, 31(3): 31-34.

[Abstract](1364) [PDF 1596KB](191)

Abstract:
The impact experiment for Mg-3Li and Mg-3Li-1Sc alloys was conducted using the Split Hopkinson Pressure Bar(SHPB) at high strain rates.The effect of minor Scandium on the impact deformation behavior and strain rate effects of Mg-3Li alloy were analyzed.The results show that the dynamic stress-strain behaviors of both alloys exhibit evident positive strain rate effect at strain rates from 1350s-1 to 3000s-1.However,the dynamic deformation behaviors of both alloys change to negative strain rate effect with the increasing strain rate.At strain rates from 1350s-1 to 3500s-1,the dynamic yield strength of Mg-3Li-1Sc alloy is enhanced significantly compared to that of Mg-3Li alloy.Under high strain rate impact loading,the strain-hardening generated by slip and twining inside grains causes the positive strain rate effect of deformation behaviors in two alloys,while the following negative strain rate effect is attribute to the initiation and propagation of micro-crack.The notable improvement of impact deformation resistance of Mg-3Li-1Sc alloy is mainly attributed to the grain refinement and the formation of small and uniformly distributed MgSc phase because minor Scandium addition.

Flow Stress Behavior of a New High Strength Al-Zn-Mg-Cu Alloy during Hot Compression Deformation

ZANG Jin-xin, ZHENG Lin-bin, ZHANG Kun, TAO Le-xiao

2011, 31(3): 35-39.

[Abstract](1473) [PDF 1789KB](259)

Abstract:
Hot compression tests of a new Al-Zn-Mg-Cu high strength alloy were carried out by thermal-mechanical simulation.The flow stress was studied at the temperature of 300～450℃,strain rates of 0.001~1s-1 and the reduction of 50%.The results show that both the temperature and strain rate have remarkable effects on the flow stress during hot deformation.The flow stress decreases with the increasing temperature and increases with the increasing strain rates.The constitutive equation of the alloy is obtained.The activation energy of the alloy is 169.92kJ/mol.

Evolution of Microstructures and Properties during Duplex Thermochemical Processing of 13Cr4Mo4Ni4VA Steel

JIANG Zhi-hua, TONG Xiao-jun, SUN Feng, WANG Guang-sheng, LI Zhi

2011, 31(3): 40-45.

[Abstract](1429) [PDF 1547KB](269)

Abstract:
Duplex thermochemical processing of 13Cr4Mo4Ni4VA steel was carried out,which involves carburizing(followed by hardening and tempering) and then nitriding.Optical microscope(OM),Scanning electron microscope(SEM),X-ray diffraction,electron probe micro-analyzer(EPMA),and microhardness tester were used to investigate the evolution of microstructures and properties during the duplex thermochemical processing of 13Cr4Mo4Ni4VA steel.The results indicate that the carbon and nitrogen introduced into 13Cr4Mo4Ni4VA steel create different zones of microstructures,cause the solubility gradient of carbon and nitrogen,and bring out different hardness fields from the surface to the core,different zones in hardened layer are responded differently during each step of duplex thermochemical processing,so the variable evolution law of microstructures and properties are followed.It is greatly different from traditional case hardening,such as carburizing,nitriding,carbonitriding and nitro-carburizing.Duplex thermochemical processing of 13Cr4Mo4Ni4VA steel leads to superior surface hardness(70HRC),deeper case depth,excellent case structure with double layers,and high bearing capacity.

Study on Diffusion Bonded Titanium Alloy to Stainless Steel with Ni+Nb Interlayers

LI Peng, LI Jing-long, XIONG Jiang-tao, ZHANG Fu-sheng, HUO Li-peng

2011, 31(3): 46-51.

[Abstract](1426) [PDF 1039KB](279)

Abstract:
Vacuum diffusion bonding between titanium alloy TC4 and austenitic stainless steel 1Cr18Ni9Ti was carried out by using conventional and ladder-like processing methods with Ni+Nb as interlayers.The microstructure and elements distribution of the joints were analyzed by OM,SEM and EDS.The mechanical properties of the joints were characterized by tensile strength test.Meanwhile the fracture surfaces were analyzed too.The results showed that Ni+Nb interlayers successfully prevent the formation of Fe-Ti intermetallic compounds,the microstructures of the transient joint from 1Cr18Ni9Ti to TC4 are Fe-Cr-Ni solid solution,Ni-Nb reaction layer,residual Nb and Nb-Ti solid solution.The weld quality of ladder-like processing joints are superior to the conventional processing joints.The maximum strength of 396MPa at 900℃ was achieved by using ladder-like processing method.The fractures occured on the mixed reaction layer that was formed by Ni3Nb and a small amount Ni6Nb7 between Ni and Nb,and this layer played a crucial role to the joint.

Effects of Hydrogen on Fatigue Crack Propagation Rate of TC4 Alloy Electron Beam Welded Joint

LIU Peng-tao, ZHAO Xiu-juan, LIU Xin, QI Jian, CHEN Chun-huan, WANG Ya-jun, REN Rui-ming

2011, 31(3): 52-55.

[Abstract](1384) [PDF 1162KB](200)

Abstract:
The hydrogenated CT specimens were adopted to measure the fatigue crack propagation rate(da/dN) of TC4 alloy electron beam welded joints at room temperature,and the fracture surface morphologies of specimens as well as the microstructures of joints were observed.The results indicated that the da/dN of hydrogenated base metal specimens were higher than the non-hydrogenated ones in near-threshold stage and rapid rupture stage,but the specimens with various hydrogen contents were little differed from each other,and hydrogen showed little effects on da/dN in stable crack propagation stage(Paris stage).During the whole crack propagation process,the da/dN of hydrogenated weld bead specimens was obviously enhanced and increased with the increment of hydrogen content.The analysis results of fracture surface morphologies showed that the crack propagation was promoted by hydrogen owing to the increase of brittleness of titanium alloy.In Paris stage,the transition of microstructure of the material has an apparent effect on da/dN,and the acicular martensite at the weld bead zone of electron beam welded joint has a higher resistance to crack propagation than lamellar α+β structure.

Microstructure and Mechanical Properties of TIG Welded-joint of Ferritic Stainless Steel

GUO Xu-ming, LIU Chun-shu, YUAN Jin-wei

2011, 31(3): 56-59.

[Abstract](1405) [PDF 846KB](203)

Abstract:
The effects of weld heat input and trace element niobium on the microstructure and mechanical properties of TIG welded-joint of ferritic stainless steel were investigated.The results showed that the ferrite grains were obviously coarsened in the coarse zone within HAZ and weld zone with weld heat input increasing.The strength and ductility of the welded-joint were decreased.The ferrite grain growth in coarse zone and weld zone was hindered through the double effects of pinning up the grain boundaries and dragging the movement of grain boundary when the small amount of niobium element was added into ferritic stainless steel.The strength and ductility of the welded-joint were improved.

Study on Al-Si/Al+Al₂O₃ Coating of AZ91D Mg Alloy by Laser Plasma Hybrid Spraying

QIAN Jian-gang, ZHANG Jia-xiang, WANG Chun, LI Shu-qing

2011, 31(3): 60-64.

[Abstract](1447) [PDF 1093KB](202)

Abstract:
An Al-Si/Al+Al2O3 coating was prepared on the AZ91D Mg alloy substrate by a new processing technique of laser plasma and with the combination of spraying,and the influences of the laser power to the structure and properties of the coating were studied.X-ray diffraction(XRD) and scanning electron microscope(SEM) were used to identify the phases and to study the morphology respectively.By the porosity ratio of the coating material was measured by using an optical microscope(OM) and the microhardness was measured using a micro Vickers hardness tester.The results show that the Al-Si transition layer improves the adhesion of the coating obviously.When the laser power is 1800W,the unmelted particles are less and the coating is the densest.The coating is composed of Al phase and α-Al2O3 phase and no surviving γ-Al2O3 phase existed.The porosity ratio decreases from 4.5% to 2.6% with the increase of the laser power.But when the power is more than 1800W,the porosity ratio increases.The hardness increases from HV0.0555 to HV0.05275 after spraying.The hardness of the surface is the largest and increases with the increase of the laser power.But when the power increases to 2000W,the hardness has no big change.

Mechanical Properties of Ni-Mn Alloy Electroformed with Abrasion-Assisted Method

LI Xue-lei, ZHU Di, ZHU Zeng-wei

2011, 31(3): 65-70.

[Abstract](1444) [PDF 777KB](226)

Abstract:
The Ni-Mn alloy was electroformed by a novel method,namely abrasion-assisted electroforming.The influence of process conditions to the micro-hardness and the tensile properties were studied.The results showed that the polishing of free particles and manganese contents jointly affected the mechanical properties of electrodeposited layer.With the increase of rotating speed,the manganese contents were increased,micro-hardness and tensile strength also were improved due to the increase of polishing effect of free particles.Following with the elevation of current density,the manganese contents also were increased,fluctuating phenomenon of mechanical properties were appeared.In certain extent of manganese contents,the mechanical properties also were constantly improved with the increase of manganese contents of coating.After annealing treatment,the abrasion-assisted strengthen of free particles was weakened in the low manganese contents.It was higher than the layer before annealing treatment only when the manganese contents were above 0.2wt%.

Study on Damage Equivalence of Composite Laminates Subjected to Low-velocity Impact and Quasi-static Indentation

YAN Li, AN Xue-feng, CAI Jian-li, ZHANG Dai-jun, YI Xiao-su

2011, 31(3): 71-75.

[Abstract](1409) [PDF 905KB](249)

Abstract:
Through the comparison of low-velocity impact testing and quasi-static indentation and testing,three kinds of relationship are obtained between the impact energy(or the quasi-static indentation force) damage area and dent depth.An analysis of these relationships indicates clearly that the damage area and dent depth can be chosen as the damage parameters to set up the damage relationship between drop-weight impact and quasi-static indentation.When impact energy or quasi-static indentation force is reached at the some value,then,the knee point appears in the three kinds of relationship curves,and the knee-points of the two tests are very close and the variation tendency is identical,which indicates that quasi-static indentation tests may replace low-velocity impact tests.Under the lower impact energy(before knee point),quasi-static indentation force approximately is equal to the maximum force caused by impact process of corresponding impact energy.By analyzing the process of the two tests,the delamination onset load in the quasi-static indentation is lower than that in the low-velocity impact,but the tendency of the load variation is similar,which further indicates the damage equivalence of composite laminates subjected to low-velocity impact and quasi-static indentation tests.

Research of Injection-Compression Molding Simulation on Transparent Plastic Plate

LI Yi-chao, ZHANG Yi-sheng, LI De-qun

2011, 31(3): 76-80.

[Abstract](1385) [PDF 1307KB](235)

Abstract:
Based on nonlinear numerical algorithm,the method of the calculation of multiphysics of full-coupled manner by the level-set equation,momentum equation and energy equation was adopted to simulate the injection-compression molding on a non-symmetric geometric plate.The study showed that in comparison with injection molding,the injection-compression molding can greatly reduce the shrinkage of the product.In addition,during the forming process the length of the fiber flow line and the temperature change can affect the shrinkage of the product.Shorter fiber flow line,more even temperature distribution can lead to lower and more even shrinkage distribution.

Effects of Heating Rates on Pre-oxidation Reactions of Polyacrylonitrile Fibers and Induction Period

YU Mei-jie, XU Yong, WANG Cheng-guo, ZHU Bo, LIN Xue, XIE Ben

2011, 31(3): 81-85.

[Abstract](1310) [PDF 1183KB](183)

Abstract:
The effects of heating rates on the cyclization and oxidation reactions of polyacrylonitrile/itaconic acid copolymer fibers under oxidative(air) and non-oxidative(argon) atmospheres were investigated by differential scanning calorimetry(DSC).The interaction between the two reactions and their mechanisms are analyzed.Fourier transform infrared spectroscopy(FTIR) was used to study the induction period of cyclization reaction.The results show that ther induction period is existed before the cyclization reaction initiated.The higher the heating rate,the longer the reduction period.With slow heating rate,the diffusion of oxygen facilitates that a part of oxidation is taken place with the cyclization reactions simultaneously.At the beginning of pre-oxidation process,oxygen can initiate the cyclization reaction and shorten the reduction period.However at the late stage,oxygen retards the cyclization reaction,but the retardant role is weakens with increasing of heating rate.

Synthesis and Properties of Copolyimides Based on ODA/TPER

CHAO Min, KOU Kai-chang, WU Guang-lei, ZHANG Jiao-qiang, ZHANG Dong-na, JIANG Yang

2011, 31(3): 86-89.

[Abstract](1575) [PDF 1080KB](232)

Abstract:
Four polyimides were synthesized via copolymerization of pyromellitic dianhydride(PMDA),4,4'-diaminodiphenyl(ODA) and 1,3-bis(4-aminophenoxy)benzene(TPER) at different monomer ratios.Their properties were characterized by Ubbelohde viscometer,XRD,SEM and TGA.The results showed that the introduction of TPER caused the change of PI films from amorphous to semicrystalline,and also the toughness of PI films was improved by the flexibel chain in the TPER molecules.When the TPER content was low,due to the cooperative effect of crystalline,the excellent thermal stability of PI films was displayed and the 5% weight loss temperature was 558℃ in N2.

Study on Thermal Degradation Mechanism of Transparent Polyurethane Based on HMDI-PTMEG

GUO Xin-tao, LI Lei

2011, 31(3): 90-94.

[Abstract](1492) [PDF 1169KB](287)

Abstract:
A series of transparent polyurethane elastomers based on HMDI,PTMEG,1,4-BDO and TMP were synthesized by two-step method,the ratio between n(PTMEG),n(HMDI) and n(1,4-BDO,TMP) was 1:3:2 and the catalyst was DBTDL.Thermal ageing experiments had been carried out at 150℃.The mechanism of thermal degradation had been investigated by DSC,FTIR and 13CNMR.Spectrum of FTIR,13CNMR had also been attributed.It indicated that thermal and mechanical properties of the elastomer had greatly changed after aging.Oxidation of ether bonds was the main reason to cause the structure and property change.

2011 Vol. 31, No. 3