Microstructure evolution of Ti5Si3 in Cu-Ti-Si alloys

The Cu-Ti-Si alloys containing in-situ formed Ti_5Si_3 are prepared.In order to clarify the Ti_5Si_3 formation processes and its microstructure characteristics,the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM),transmission electron microscopy (TEM) and X-ray diffraction (XRD).It is found that the eutectic Ti_5Si_3 phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix.In addition,there is Cu in the center of many Ti_5Si_3 rods,resulting in a core-shell structure.With the increase of the cooling rate,Ti_5Si_3 distributes more uniformly,and the diameter of Ti_5Si_3 significantly decreases,with a minimum size of less than 100 nm,while the aspect ratio of Ti_5Si_3 increases.     

Interfacial reactions and diffusion path in partial transient liquid-phase bonding of Si_3N_4/Ti/Ni/Ti/Si_3N_4

1INTRODUCTIONPartialtransientliquid-phasebonding(PTLP),whichhastheadvantagesofbothbrazingandsolid-statediffusionbonding,isanewtechnologyusedforceramicjoining['~'].Recently,theauthorshavebeenstudyingthepartialtransientliquid-phasebondingofSi,N'/Ti/Ni/Ti/SisN'withtheemphasesonthemi-grationbehavi0roftheinterfaceandtheselectionofthebondingparameters[#1.Theinterfacialre-actionsbetweenmetalsandceramicsandthein-terfacestructuresareboththekeyfact0rswhichdeterminetheinterfacialstrength[','J.A…     

FRACTURE MECHANISM IN Ti_3Al Si Nb ALLOYS

ＦＲＡＣＴＵＲＥＭＥＣＨＡＮＩＳＭＩＮＴｉ_３Ａｌ＋Ｓｉ＋ＮｂＡＬＬＯＹＳＷＵＪｉａｎｓｈｅｎｇ；ＺＨＡＮＧＬａｎｔｉｎｇ；ＱＩＵＧｕｏｈｕａ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ，ＳｈａｎｇｈａｉＪｉａｏＴｏｎｇＵｎｉｖｅｒｓｉ?..     

SOLID REACTION BETWEEN PRESSLESS SINTERED Si_3N_4 SUBSTRATE AND Ti-DEPOSITED FILM

The chemical reaction at solid state between the pressless sintered Si_3N_4 substrate and Ti-de-posited film has been studied by X-ray diffraction analysis.The reaction all depends upon thetemperature.It seems no reaction below 973 K:Ti_2N and Ti_5Si_3 form from 1073 to 1123 K:TiN and Ti_5Si_3 form at 1173 K,TiN and Ti_5Si_4 form at 1273 K;while the titanium film di-minishes completely.The lattice parameter of Si_3N_4 is unchanging thrioughout postannealing.This implies that the Ti atoms never dissolve into the Si_2N_4 lattice.     

无压烧结Si3N4与表面镀钛膜之间的固态化学反应过程

用X射线衍射技术研究了在Si_3N_4陶瓷与表面镀钛膜之间的固态化学反应过程,当反应温度不超过973K时,Ti与Si_3N_4之间不反应;温度在1073—1123K时,反应产物为Ti_2N和Ti_5Si_3,温度达到1173K时,反应产物为TiN和Ti_5Si_4,温度达到1273K时,反应产物为TiN和Ti_5Si_4。在整个反应过程中,Si_3N_4陶瓷基体相的晶格常数未发生变化,说明Ti原子不能溶入Si_3N_4陶瓷的晶格之中。     

Ti/Ti_3SiC_2复合材料的界面结构

研究了Ti_3SiC_2和Ti在1573K、20MPa压力下的相互联接及界面结构。结果表明在该温度下二者之间可以相互联接并形成反应层,反应层的主要成分是Ti_5Si_3和TiC_x,各层之间有明显的界面存在,在界面两端硅含量的变化十分明显。     

Ti_3Si_(0.6)Al_(0.6)C_(1.98)陶瓷的制备与性能研究

采用原位热压工艺制备了高纯Ti_3Si_0.6Al_0.6C_1.98陶瓷,并测试了性能.以单质的Ti、Si、Al和石墨粉为原料,摩尔比Ti:Si:Al:C=3:0.6:0.6:1.98,在1500 ℃,30 MPa压力下保温1 h,高纯Ar气保护,制备试样的主要物相为Ti_3Si_0.6Al_0.6C_1.98.制备的Ti_3Si_0.6Al_0.6C_1.98陶瓷的密度为(4.43±0.23) g/cm~3,电阻率为(0.31±0.01)μΩ·m,抗弯强度为(245.46±22.04) MPa,维氏硬度为(2.91±0.32) GPa, 断裂韧性为(5.63±0.39) MPa·m~(1/2).Ti_3Si_0.6Al_0.6C_1.98陶瓷中晶粒以板状晶为主,晶粒层状结构明显,断口形貌显示主要为穿晶断裂,晶粒的分层断裂、微裂纹的偏转桥接及滑移使材料具有独特的压痕特征.     

陶瓷/AgCuTi/不锈钢钎焊连接界面组织与结构

采用Ag-Cu-Ti钎料对日用陶瓷与1Cr18Ni9Ti不锈钢进行了钎焊连接.用扫描电镜、能谱仪以及X射线衍射仪对接头的微观组织形貌、特征点的成分以及钎焊接头的物相等进行了分析研究.结果表明,接头界面处形成了多种化合物,包括TiO,TiSi_2,Ti_5Si_3和Fe_2Ti.当温度为850℃,保温时间为5 min时,接头界面结构为1Cr18Ni9Ti不锈钢/Fe_2Ti/Ag[s,s]+Cu[s,s]+Fe_2TiO+Ti_5Si_3+TiSi_2/陶瓷.当钎焊温度较高或保温时间较长时,界面反应层厚度增加,界面中基体相Ag[s,s],Cu[s,s]所占比例显著减小.

Abstract：

Domestic ceramics and lCrl8Ni9Ti stainless steel were brazed using Ag-Cu-Ti filler metal. Microstructure, the component of characteristic points and the phases of brazing joints were studied by scanning electronic microscopy ( SEM) , energy distribution spectrometer (EDS) and x-ray diffraction (XRD). The results show that several kinds of intermetallics such as TiO_2, TiO, TiSi_2 , Ti_5 Si_3 and Fe_2 Ti were formed. The interfacial structure of joints is 1Cr18Ni9Ti stainless steel/Fez Ti/Ag[ s, s] + Cu[s,s] + Fe_2Ti/TiO_2 + TiO + Ti_5Si_3 + TiSi_2/ceramics when brazing temperature and time are 850 ℃ and 5min, respectively. The depth of interfacial reactive layer increases and the ratio of matrix phase Ag [ s, s ], Cu [ s, s ] which are in the middle of interface reduces evidently as brazing temperature is very high or holding time is very long.     

用非晶态合金作中间层对Si_3N_4陶瓷进行扩散焊连接

研制了两种非晶态物质Ｃｕ_（５０）Ｔｉ_（５０），Ｃｕ_（５０）Ｔｉ_（５０）Ｂ作为对Ｓｉ_３Ｎ_４扩散焊连接的中间层材料．研究结果表明：用非晶态作为中间层可改善工艺条件，降低扩散焊温度；非晶态中间层接头比其相应晶态中间层接头的剪切强度有明显提高．其中硼对提高接头剪切强度贡献很大．用非晶态Ｃｕ_（５０）Ｔｉ_（５０）Ｂ作中间层时，接头强度最高可达３４０ＭＰａ用晶态和非晶态Ｃｕ_（５０）Ｔｉ_（５０），Ｃｕ_（５０）Ｔｉ_（５０）Ｂ作中间层对Ｓｉ_３Ｎ_４进行扩散焊连接的机制是：活性元素Ｔｉ向陶瓷界面扩散和富集并与Ｓｉ_３Ｎ_４发生反应生成界面相ＴｉＮ，ＴｉＳｉ_２等．从而实现连接．     

Joining of Si_3N_4-Si_3N_4 using CuNiTi alloy brazing filler

01lltrodnotionOwingtoitssuperiormechanicalproperties,thesiliconnitrideceramicisbecomingoneofthemostpotentialstructurematerialsinengineeringapplications.Insomecases,theSt3N4ceramicusuallyneedstobejoinedwithitselformetals.Recently,theAgCuTibrazingfillerInetalshavebeentvidelyusedl'-,I,buttheycontainratherhighquantityofAgupto57%Whichisanexpensivekindofmetal.Therefore.itisnecessarytodevelopanewkindofbracingfillerInetalsx\'ithsimil:ll'propertiestothatofAgCuTibrazingalloysbutwithoutsilver.Thewe…     

Ti53Cu27Ni12Hf3Al7Si3B1大块金属玻璃的制备及性能研究

用单辊甩带法和铜模铸造法制备了新型Ti基大块金属玻璃Ti53Cu27Ni12Hf3Al7Si3B1.DSC、DTA研究表明该合金具有较高的热力学稳定性,其第1晶化温度Tx1、玻璃转变温度Tg、过冷液相区间ΔTx以及约化转变温度Trg分别为705、750、45、0.63 K.压缩性能研究其压缩断裂强度、弹性模量和压缩塑性变形量分别为2 304 MPa、120 GPa和1.1%.研究发现,具有复杂拓扑结构的原子配比提高了Ti53Cu15Ni18.5Al7Hf3Si3B0.5大块金属玻璃的力学性能和热力学性能.     

放电等离子烧结制备SiC/Ti_3SiC_2复合材料

以钛粉、硅粉和石墨粉为原料,采用放电等离子烧结制备l了含20%(摩尔分数,下同)siC的SiC/Ti_3SiC_2复合材料,并研究了烧结助剂Al对该复合材料的性能影响.利用X射线衍射分析样晶相组成.运用扫描电镜分析材料的最微组织和断口形貌,并对试样的密度、硬度和抗弯强度进行了测定.结果表明,按Ti_3Si_(1.2)C_(2-)20%SIC和(Ti_3Si_(1.2)C_2-20%SIC)+2wt%Al进行成分配比,可制得纯度较高的Ti_3SiC_2-20%SiC复合材料,两者都含有少量未反应完全的石墨.未加Al的样品还含有微量的TiSi_2杂质;添加铝对样品的密度并没有明显影响,但对显微硬度有较大影响.含铝样品的显微硬度明显低于不含铝的样品;含铝和不含铝试样的三点抗弯强度分别为221.0、231.7 MPa.     

稀土钇对Ti-Si共晶合金微观组织和力学性能的影响

研究了稀土钇对Ti-Si共晶合金的微合金化作用.结果显示,适量的钇可以提高合金的室温压缩塑性和强度,但合金的断裂方式并没有得到有效改变.微观组织表明,适量钇的加入,改变了原始铸态组织中共晶团的数量和尺寸.     

Microstructure and dry sliding wear behavior of laser clad AlCrNiSiTi multi-principal element alloy coatings

The approximately equimolar ratio AlCrNiSiTi multi-principal element alloy(MPEA) coatings were fabricated by laser cladding on Ti-6A1-4V(Ti64) alloy.Scanning electron microscopy(SEM),equipped with an energy-dispersive spectroscopy(EDS),and X-ray diffraction(XRD) were used to characterize the microstructure and composition.Investigations show that the coatings consist of(Ti,Cr)_5Si_3 and NiAl phases,formed by in situ reaction.The phase composition is initially explicated according to obtainable binary and ternary phase diagrams,and the formation Gibbs energy of Ti_5Si_3,V_5Si_3 and Cr_5Si_3.Dry sliding reciprocating friction and wear tests of the AlCrNiSiTi coating and Ti64 alloy substrate without coating were evaluated.A surface mapping profiler was used to evaluate the wear volume.The worn surface was characterized by SEM-EDS.The hardness and wear resistance of the AlCrNiSiTi coating are well compared with that of the basal material(Ti64).The main wear mechanism of the AlCrNiSiTi coating is slightly adhesive transfer from GCr15 counterpart,and a mixed layer composed of transferred materials and oxide is formed.     

Ti细化A357铝合金中的析出相

用透射电镜研究了Ｔｉ细化Ａ３５７铝合金组织中析出相的形态,组成及其对合金变形,性能的影响。结果表明：Ｔｉ细化Ａ３５７铝合金组织中主要存在着弯曲状的Ｔｉ３Ｓｉ５,直杆状的ＴｉＡｌ３及短棒状的Ａｌ和Ｔｉ为主,含Ｍｇ和Ｓｉ的化合物,拉伸变形过程中,析出相阻挡和缠结位错,对合金有一定的强化作用,和过程中,析出相周围先形成表面无析出区,延长时效时间后该区消失,对合金的拉伸性能造成的一定的影响。     

用热扩散方法在Ti-6Al-4V合金表面获得铝化物和硅化物涂层

采用固体粉末包装热扩散方法,对Ti-6Al-4V合金分别进行表面渗铝和渗硅处理,以提高该合金的抗高温氧化性能。结果表明:Ti-6Al-4V合金表面形成的铝化物涂层的金相组织为单层结构,其上有少量贯穿裂纹存在;主要相结构是TiAl_3。而硅化物涂层的金相组织则为双层结构,外层较厚,呈柱状晶,由TiSi_2相组成;内层则较薄,由Ti_5Si_4相组成。表面渗铝和渗硅处理都可以大大提高Ti-6Al-4V合金的抗高温氧化性能。     

Ti-Nb-Si基超高温合金Si-Cr共渗抗氧化涂层的显微组织

采用在1 250、1 350和1 400 ℃ Si-Cr包埋共渗10 h的方法,在Ti-Nb-Si基超高温合金表面制备了Cr改性硅化物涂层.结果表明:各温度下制备的涂层均具有多层复合结构;随包埋共渗温度的升高,涂层外层和中间层的组成相都发生改变.经1 250 ℃,10 h Si-Cr共渗时涂层外层为(Ti, X)_5Si_3(X代表Nb、Hf和Cr元素),中间层为(Ti, X)_5Si_4,过渡层(Ti, X)_5Si_3很薄;当提高共渗温度至1 350 ℃时,涂层外层中Cr含量明显提高,外层除了(Ti, X)_5Si_3外,还出现含Cr的三元相(Nb_(1.95)Cr_(1.05))Cr_2Si_3,中间层由(Ti, X)_5Si_4和(Ti, X)_5Si_3两相组成,而过渡层((Ti, X)_5Si_3)增厚;继续提高共渗温度至1 400 ℃时,涂层外层主要由(Nb_(1.95)Cr_(1.05))Cr_2Si_3三元相组成,中间层已全部由(Ti, X)_5Si_3相组成,在过渡层与基体间还存在不连续的块状(Nb, Ti)_3Si相,Si-Cr共渗温度对Cr扩散的影响更为显著.     

Al_2O_3/(Ag_(72)Cu_(28))_(97)Ti_3/Ti-6Al-4V界面结构及性能研究

在1．8ks,1073K－1173K条件下对Al2O3/(Ag72Cu28)97Ti3/Ti-6Al-4V进行了钎焊试验。通过扫描电镜、波谱、能谱、X射线衍射界面结构进行了分析。小于1123K的界面结构为Al2O3/Cu2Ti4O/Cu4Ti3/Ag-Cu共晶＋富Ag相＋Ti固溶体;1173K的界面结构为Al2O3/Cu3TiO5 CuAl2O4/Cu4Ti3/富Ag相。采用拉剪试验测试了接头剪切强度。在1．8ks,1123K时剪切强度最高达到189MPa,大于或小于1123K接头强度呈下降趋势。     

La2O3-Mo5Si3/MoSi2复合材料的力学性能和高温氧化行为

通过自蔓延高温合成了稀土协同Mo5Si3复合强韧化MoSi2的复合粉末,研究了La2O3-Mo5Si3/MoSi2复合材料的室温力学性能和高温氧化特性。结果表明:与纯MoSi2相比,稀土和Mo5Si3细化了材料的晶粒,提高材料的室温弯曲强度和断裂韧性,其强化机制为细晶强化,韧化机制为细晶韧化、裂纹偏转、裂纹分支和微桥接;当Mo5Si3含量不超过30%(摩尔分数)时,随着Mo5Si3含量的增加,材料的抗氧化性能降低,而RE-40%Mo5Si3/MoSi2(摩尔分数)复合材料出现粉化现象;RE-Mo5Si3/MoSi2复合材料抗氧化性的降低,主要是由于Mo5Si3较差的抗氧化性、材料致密度的降低以及晶粒细化的结果;0.8%稀土(质量分数)协同5%Mo5Si3(摩尔分数)的RE-Mo5Si3/MoSi2复合材料具有较好的综合力学性能和高温抗氧化特性。     

Al_2O_3/(Ag_(72)Cu_(28))_(97)Ti_3/Ti-6Al-4V界面结构及性能研究

在 1.8 ks,10 73 K～ 1173 K条件下对 Al2 O3/ ( Ag72 Cu2 8) 97Ti3/ Ti- 6Al- 4 V进行了钎焊试验。通过扫描电镜、波谱、能谱、X射线衍射对界面结构进行了分析。小于 112 3 K的界面结构为 Al2 O3/ Cu2 Ti4 O/ Cu4 Ti3/ Ag- Cu共晶 +富 Ag相 + Ti固溶体 ;1173 K的界面结构为 Al2 O3/ Cu3Ti O5+ Cu Al2 O4 / Cu4 Ti3/富 Ag相。采用拉剪试验测试了接头剪切强度。在 1.8ks,112 3 K时剪切强度最高达到 189MPa,大于或小于 112 3 K接头强度呈下降趋势。