Nd-RICH PHASE PARTICLES IN AS-FORGED Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd ALLOY

1.IntroductionTi-5AL4Sn-2Zr1Mo-0.25Si-1Nd(calledTi-55all0y)wasevaluatedforlongtermcreepapplicationat55OoC[1].NdandSnasinc0herentsec0ndphaseparticlesdistributewh-formlyintheTi-55alloy,whichimprovecreepresistanceandfatiguestrength.[2]ThestatisticaJresultsshowedthatthemajorityoftheseparticlesareelliptical[3].However,theinteriorstructureofthesec0ndphaseparticlesintheas-forgedTi-55alloyareunknown.Earlyinvestigati0nsI']demonstratedthattheaddition0fsmallqualltities0ferbiumandyttriumtobinarytit…     

EFFECT OF HIGH TEMPERATURE DEFORMATlON ON MORPHOLOGY OF Nd－RICH PHASE PARTICLES IN Ti－5Al－4Sn－2Zr－1MO－0．25Si－1Nd ALLOY

ＥＦＦＥＣＴＯＦＨＩＧＨＴＥＭＰＥＲＡＴＵＲＥＤＥＦＯＲＭＡＴｌＯＮＯＮＭＯＲＰＨＯＬＯＧＹＯＦＮｄ－ＲＩＣＨＰＨＡＳＥＰＡＲＴＩＣＬＥＳＩＮＴｉ－５Ａｌ－４Ｓｎ－２Ｚｒ－１ＭＯ－０．２５Ｓｉ－１ＮｄＡＬＬＯＹ￥ＬＩＧｅｐｉｎｇ;ＧＵＡＮＳｈａｏｘｕ...     

Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd合金焊接性

考察了Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd合金焊接接头力学性能。结果表明，Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd钛合金的焊接热影响区存在硬化倾向，塑性不足。焊前预热150℃可使焊接热影响区塑性明显改善。通过改变焊缝合金系统和焊后热处理制度等工艺措施，可以调整焊缝的综合力学性能，使之达到技术指标要求。文中还探讨了Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd合金焊接脆性的机理，认为延晶界成串分布的富钕相和晶内的马氏体转变组织是根本原因。     

DISTRIBUTION OF Nd-RICH PHASE PARTICLES IN AS-CAST Ti-5Al-4Sn-2Zr-lMo-0.25Si-1Nd ALLOY

For the as一cast Ti一55 alloy,the morphology of the alloy riser consists of coarse dendritezone and equiaxial grain zone the second phase particles are 2.0～25 μm in diameterSome particles appear at grain boundaries,the others precipitate within grains the shapesof the particles are mainly ellipsoids,and a few kinds of short needle-like and blockymorphologies The Nd-rich phase particles are enriched in the liquid be fore the interfaceand are engulfed along the solidification plane-front Finally bands of Nd-rich phase particles form parallel to the advancing solidification plane-front     

Ti-5.8Al-4.8Sn-2Zr-1Mo-0.35Si-0.70Nd合金中富钕稀土相研究

针对Ti-5.8Al-4.8Sn-2Zr-1Mo-0.35Si-0.70Nd粉末冶金高温钛合金中富钕稀土相的形成、尺寸、分布、形态、长大及结构特征进行了系统研究。结果表明:快速凝固态高温钛合金粉末中稀土相为液态析出相,其尺寸大部分在50~250 nm之间,弥散分布在基体中;晶内稀土相多为球状,晶界稀土相多为椭球状,其长轴平行于晶界;TEM观察到的稀土相的尺寸和分布与理论计算相符合;快速凝固高温钛合金粉末经过700~1000℃/110 MPa/0.5 h热等静压成形后,快速凝固过程中已析出的稀土相尺寸变化不大;同时细小的稀土相从过饱和的基体中大量固相析出;经过1200℃/140 MPa/3 h热等静压成形后,稀土相颗粒尺寸大部分在150~500 nm之间,有明显长大;稀土相的高分辨图像及同心衍射环花样表明,快速凝固高温钛合金粉末中的稀土相由5~10 nm的纳米晶组成,经过1200℃热等静压成形处理后的稀土相仍由纳米晶组成,而且纳米晶的尺寸没有明显变化;但是稀土相的"基体"上明显出现富Sn元素的"第二相"颗粒,结构变得复杂。     

Al—Ti—B晶粒细化合金中的有效形核相

研究了ＡｌＴｉＢ晶粒细化合金中各化合物相ＴｉＡｌ３、ＴｉＢ２和ＡｌＢ２对铝晶粒的细化作用。结果表明，ＴｉＡｌ３相是有效形核相，ＴｉＢ２和ＡｌＢ２相不能单独作为形核相，Ｂ对ＡｌＴｉＢ的细化作用有显著影响，但Ｂ及硼化物不能单独影响细化过程，而是富集在ＴｉＡｌ３相中对细化过程产生重要影响。     

NUCLEATION BEHAVIOR OF Al_8Fe_4Nd PHASE IN RAPIDLY SOLIDIFIED Al-Fe-V-Si-Nd ALLOY

The microstructure of Al-Fe-V-Si-Nd alloy prepared by rapid solidification (RS) processing was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). The phase selection of the alloy during solidification and the nucleation behavior of Al8Fe4Nd phase were analyzed within the framework of time-dependent nucleation theory. The incubation time for Al8Fe4Nd phase was found shorter and the nucleation rate higher than those of α-Al. The results indicate the nucleation of Al8Fe4Nd phase is heterogeneous and the dispersoids of Al8Fe4Nd form as primary particles from the liquid, which is consistent with experimental observation.     

NUCLEATION BEHAVIOR OF Al8Fe4Nd PHASE IN RAPIDLY SOLIDIFIED AI-Fe-V-Si-Nd ALLOY

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STUDY ON CONSTITUTIVE RELATIONSHIP OF Ti-5Al-2Sn-2Zr-4Cr-4Mo ALLOY AND SIMULATION OF HOT FORMING PROCESSES

.~theSofar,finiteelementmethodhaswidelybeenusedinmetalfoeingprocesses,whichcanhelptoshortenthedevelopmentcycleandreducetheproductcosts.ConstitutiverelationshipisabridgebetweenthedefonnationbehaViorofmaterialsandallkindsOfthermomechanicalparameters,anditisalsoapresupPOsitiontothesimulationOfmetaldeformationprocessesbyusingfiniteelementmethod.Fwhermore,itisusuallynon--linearandcomplex,owingtoavallationinstructUredabingplasticdefonnation,Particularlyoccultinginsupendloys.FOrmanyyears,researche…     

工业用Ti-6Al-2Zr-1Mo-1V合金铸锭剖析

研究了工业用Ti-6Al-2Zr-1Mo-1V合金铸锭内化学成分的分布、结晶组织特点及铸态材料的室温性能.研究表明铸锭的化学成分均匀、冶金质量良好,能够满足航空用材需求.     

Ti-6Al-2Zr-1Mo-1V合金厚板的组织与性能

Ti-6Al-2Zl-1Mo-1V厚板4种典型组织形貌与性能有一定的对应关系.等轴组织具有较高的强度和塑性,片状组织具有较高的冲击和断裂韧性.     

快速凝固Ti－55合金中稀土第二相双模型分布的形成

对快速凝固Ｔｉ－５Ａｌ－４Ｓｎ－２Ｚｒ－１Ｍｏ－０．２５Ｓｉ－１Ｎｄ（Ｔｉ－５５）高温钛合金９８０℃，５ｈ处理样品的透射电镜分析表明，稀土第二相在合金中以双模型分布，较小颗粒尺寸为２０－８０ｎｍ，较大颗粒尺寸为２００－３００ｎｍ．在扩散控制第二相粒子长大动力学方程的基础上，运用扰动理论，分析了第二相颗粒尺寸的定态解的稳定性，并验证了双模型分布．     

变形量对Ti-6Al-2Zr-1Mo-1V合金组织和性能的影响

研究了两相区总变形量对Ti-6A-2Zr-1Mo-1V合金组织与力学性能的影响.结果表明,在相同的热处理制度下,随着变形量的增加,合金的室温拉伸、高温拉伸性能及ak相应增加,合金的组织变得细小、均匀,且弥散的α颗粒逐渐增多.合金中弥散α颗粒的增多可能是合金强度提高的主要原因.     

显微组织对TC11合金高温保时疲劳敏感性的影响

详细研究了等轴、三态、网三种组织对ＴＣ１１合金（Ｔｉ－６．５Ａｌ－３．５Ｍｏ－１．５Ｚｒ－０．３Ｓｉ）５２０℃高温保时疲劳敏感性的影响。结果表明,当在每次循环峰值保时３ｍｉｎ时,三种显微组织的ＴＣ１１合金均呈现疲劳寿命显著下降,其中等轴组织下降最大,三态组织其次,网篮组织最小。ＳＥＭ和ＴＥＭ观察显示,等轴和三态组织的保时敏感性是以大量准解理断裂和车辙状平面滑移为其断裂特征,且准解理断裂和平面滑移随     

Influence of heat treatments on microstructure and mechanical properties of laser additive manufacturing Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy

The effect of heat treatments on laser additive manufacturing (LAM) Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy (TC17) was studied aiming to optimize its microstructure and mechanical properties. The as-deposited sample exhibits features of a mixed prior β grain structure consisting of equiaxed and columnar grains, intragranular ultra-fine α laths and numerous continuous grain boundary α (α_GB). After being pre-annealed in α+β region (840 °C) and standard solution and aging treated, the continuous α_GB becomes coarser and the precipitate free zone (PFZ) nearby the α_GB transforms into a zone filled with ultra-fine secondary α (α_S) but no primary α (α_P). When pre-annealed in single β region (910 °C), all α phases transform into β phase and the alloying elements distribute uniformly near the grain boundary. Discontinuous α_GB and uniform mixture of α_P and α_S near grain boundary form after subsequent solution and aging treatment. The two heat treatments can improve the tensile mechanical properties of LAM TC17 to satisfy the aviation standard for TC17.     

快速凝固Al─3．18Ti─0．65C合金中TiC相的形成和分布特征

采用快速凝固技术在Ａｌ─３．１８Ｔｉ─０．６５Ｃ（ｗｔ─％）合金中获得了呈弥散分布的单一ＴｉＣ相颗粒，尺寸为３０─１００ｎｍ，原子组成为ＴｉＣ＿（０．７６）．结合常规和快速凝固组织的分析对比，并以热力学分析为基础。研究和探讨了ＴｉＣ相的形成过程和机制     

Cavity nucleation during hot forging of Ti-6Al-2Zr-1Mo-1V alloy with colony alpha microstructure

The initiation sites and influencing factors of cavity nucleation were investigated for a Ti-6Al-2Zr-1Mo-1V alloy with lamellar starting structure,using the isothermal hot compression test.All samples were deformed to a true strain of 0.70 in the temperature range of 750-950°C and strain rate range of 0.001-10 s-1.The corresponding microstructures were observed by means of the metallurgical microscopy and scanning electron microscopy(SEM).It was found that all cavities occurred at the bulge regions of the compression specimens.Most of cavities nucleated along prior beta boundaries oriented 45°to the compression axis,while others nucleated at the interfaces of lamellar alpha colonies.Cavity nucleation was inhibited with increasing the volume fraction of beta phase and the volume fraction spheroidized of lamellar alpha phase.     

Flow Behavior and Constitutive Equation of Ti-6.5Al-2Sn-4Zr-4Mo-1W-0.2Si Titanium Alloy

In order to get a reliable constitutive equation for the finite element simulation, flow behavior of Ti-6.5Al-2Sn-4Zr-4Mo-1W-0.2Si alloy under high temperature was investigated by carrying a series of isothermal compression tests at temperatures of 1153-1293 K and strain rates of 0.01-10.0 s^?1 on the Gleeble-1500 simulator. Results showed that the true stress-strain curves exhibited peaks at small strains, after which the flow stress decreased monotonically. Ultimately, the flow curves reached steady state at the strain of 0.6, showing a dynamic flow softening phenomenon. The effects of strain rate, temperature, and strain on the flow behavior were researched by establishing a constitutive equation. The relations among stress exponent, deformation activation energy, and strain were preliminarily discussed by using strain rate sensitivity exponent and dynamic recrystallization kinetics curve. Stress values predicted by the modified constitutive equation showed a good agreement with the experimental ones. The correlation coefficient (R) and average absolute relative error (AARE) were 98.2% and 4.88%, respectively, which confirmed that the modified constitutive equation could give an accurate estimation of the flow stress for BT25y titanium alloy.     

Ti-4.5Al-5Mo-1.5Cr合金增韧的价电子理论研究

利用余氏固体与分子经验电子理论和程氏改进的TFD理论计算了Ti-4.5Al-5Mo-1.5Cr与Ti-6Al-4V两种合金的相空间及其异相界面价电子结构。利用价电子结构参数－相结构因子和界面结合因子，分析讨论了合金元素Mo,Cr和V对Ti-4.5Al-5Mo-1.5Cr与Ti-6Al-4V钛合金相空间及其异相界面价电子结构的影响，进而在电子结构层次上揭示了Ti-4.5Al-5Mo-1.5Cr合金增韧的微观本质原因。