碳含量对自生TiCP增强钛基复合材料组织的影响

采用反应自生法制备了ＴｉＣ颗粒增强钛合金基复合材料,并通过ＸＲＤ,ＳＥＭ对复合材料的相组成和微观组织进行了研究。结果表明：在Ｔｉ－６Ａｌ－１．８Ｃ中主要存在Ｔｉ和ＴｉＣ两种相。ＴｉＣ以树枝状初生ＴｉＣ和短棒状共晶ＴｉＣ两种形态存在。对ＴｉＣ晶格常数的计算结果表明,ＴｉＣ的衍射峰存在一定的偏移,主要是由于ＴｉＣ中存在Ｃ空位。研究了Ｃ含量对材料组织和ＴｉＣ形貌的影响。结果表明：Ｃ含量对基体组织基本没有影响,但是随着Ｃ含量由１．９８％减少到０．３９％,粗大的树枝状ＴｉＣ逐渐消失,ＴｉＣ以短棒状为主,部分呈羽毛状。     

自生TiC增强钛基复合材料的微观组织

采用反应自生法制备了ＴｉＣ颗粒增强钛合金基复合材料,研究了复合材料的相组成和微观组织。在Ｔｉ－６Ａｌ－２Ｃ合金中存在Ｔｉ和ＴｉＣ两种相。ＴｉＣ权树枝状初生Ｔｉｃ和短棒状共晶ＴｉＣ两种开头存在,其中共晶ＴｉＣ主要存在于晶界,特别是三角晶界处。ＴｉＣ晶格常数的计算结果表明ＴｉＣ的衍射峰存在一定的偏移,主要是由于存在于ＴｉＣ中的Ｃ空位引起晶格畸变。随着Ａｌ含量的增加,初生ＴｉＣ由发达粗大的树枝晶变为不发达的树枝晶,当Ａｌ含量为３５％时变为短棒状和薄片状的ＴｉＣ。基体组织也相应地由单一的Ｔｉ基体变为Ｔｉ和Ｔｉ３Ａｌ的两相基体以及Ｔｉ３Ａｌ和ＴｉＡｌ两相基体。根据相图分析了组织变化的主要原因。     

Ti_2AlC-TiB_2对TiAl基复合材料组织及力学性能的影响

以Ti、Al和B4C为原料,采用真空电弧熔炼的方法制备了含Ti_2AlC-TiB_2增强相的TiAl基复合材料;分析了添加不同含量的Ti_2AlC-TiB_2对复合材料的物相组成、组织结构及力学性能的影响,并探讨了微观组织结构的形成机制。结果表明:Ti_2AlC-TiB_2/TiAl复合材料主要由TiAl、Ti3Al、TiB_2和Ti_2AlC等物相组成,TiB_2和Ti_2AlC分布在层片状的TiAl+Ti3Al基体中;随着原料中B4C含量的增多,复合材料组织中Ti_2AlC-TiB_2含量增多,且TiAl基体的晶粒被明显细化,TiB_2和Ti_2AlC分布于基体晶界或晶内。Ti_2AlC主要为层片状和板条状,尺寸5~15μm,而TiB_2颗粒形态与其含量有关,当Ti_2AlC-TiB_2含量小于20wt%时,TiB_2颗粒呈针棒状,尺寸为0.5~5μm,当Ti_2AlC-TiB_2含量增加到30wt%时,TiB_2颗粒主要呈块状,尺寸为5~20μm。Ti_2AlC由TiC与Ti-Al熔体发生包晶反应生成,Ti_2AlC和TiB_2的形成提高了Ti_2AlC-TiB_2/TiAl复合材料的硬度、塑性和抗压强度。当4Ti+Al+B4C的加入量为10wt%时,复合材料的变形量比纯TiAl提高14%,而抗压强度达到最高值1 591 MPa。Ti_2AlC和TiB_2通过裂纹偏转、颗粒钉扎、拔出等机制对Ti_2AlC-TiB_2/TiAl复合材料起到增强增塑的作用。     

原位自生TiCp/6061复合材料的组织、硬度及耐磨性能

采用接触反应法制备了原位自生Ti Cp/6061复合材料,利用XRD和SEM对复合材料进行物相分析及微观形貌观察,用6061铝合金基体材料作为对比,研究了增强粒子含量对复合材料硬度和摩擦磨损行为的影响。结果表明,采用接触反应法,以Ti粉、C粉和Al粉作为生成Ti C增强相的原材料,可直接在6061铝合金基体中原位生成Ti C颗粒,Ti C颗粒呈规则多边形,尺寸为0. 5～1μm。随着增强粒子含量的增加,原位自生Ti Cp/6061复合材料的硬度明显提高,T6热处理后5%(质量分数)的Ti Cp/6061复合材料的硬度为120. 5HBS,比基体6061铝合金提高了28. 1%。这是Ti C颗粒对6061基体材料的位错强化和细晶强化综合作用的结果。此外,随着增强粒子含量的提高,原位自生Ti Cp/6061复合材料的耐磨性也增强; T6热处理后,在100 N恒压作用下与GCR15材料对磨300 s,基体6061铝合金失重是5%(质量分数) Ti Cp/6061复合材料的2倍。其原因在于Ti C颗粒含量的提高减小了对磨材料与复合材料的有效接触面积,从而增强了原位自生Ti Cp/6061复合材料的耐磨性能。     

稀土Dy对Cu-Cr-Ti合金时效态组织和性能的影响

为了研究稀土Dy对Cu-Cr-Ti合金组织和性能的影响,采用金相显微镜、X射线衍射仪、扫描电子显微镜和能谱仪对添加不同含量Dy的时效态Cu-Cr-Ti合金析出相形貌、组织和成分进行了表征和分析,并对合金的硬度和导电率进行了测试.研究表明:Cu-0.3Cr-0.2Ti合金中形成新相CuTi3;富Dy相以4种形态存在,在Cu基体上以球形、柳叶状、颗粒状存在,晶界上以短棒状析出.经500℃保温1h时效处理后,Cu-0.3Cr-0.2Ti合金中0.1%Dy的添加有效地提高了合金的硬度和导电率,其硬度和导电率分别达138.8HV和98.3%IACS.     

SiC晶须对反应合成多孔TiB_2-TiC复合材料的影响

以Ti、B_4C和SiC晶须(SiC_w)为原料,采用自蔓延高温合成法制备了多孔TiB__2-TiC复合材料。讨论了SiC_w含量对TiB__2-TiC复合材料物相、组织形貌、孔隙率和抗压强度的影响。结果表明:不添加SiC_w时,复合材料中主要物相为贫硼相TiB和Ti_3B_4以及TiC和少量TiB__2;在5Ti+B_4C体系中加入SiC_w后,贫硼相TiB和Ti_3B_4逐渐减少直至消失,而出现富硼相TiB__2和TiC的含量增加。随着SiC_w含量的增加,复合材料的孔隙率逐渐增加,由38.46%增加至5_2.78%。当SiC_w含量小于1.0时,随着SiC_w含量的增加,多孔TiB_2-TiC复合材料的抗压强度明显增加,当SiC_w含量为1.0时,复合材料的抗压强度达到最大值56.04MPa。Ti与SiC_w反应会生成TiC、Ti_3SiC_2和TiSi_2等物相,消耗一定量的Ti,使得与B4C反应的Ti量减少,从而促进富硼相TiB_2形成和TiC的增多。并且在SiC_w表面形成颗粒状TiC或者层片状Ti_3SiC_2,增加SiC_w与TiB_2-TiC基体之间的结合,更有利于发挥SiC_w的强化作用。     

激光熔覆沉积钛基复合材料的组织及性能

通过在激光熔覆沉积过程中向熔池内送入一定比例纯Ti粉和B4C颗粒，直接制备出钛基复合材料，分析了所制备材料的微观组织、相组成及性能。结果表明，在激光熔覆沉积过程中，Ti粉和B4C颗粒发生原位反应，生成与基体界面结合良好的TiC和TiB增强相，TiC为短棒状或颗粒状，TiB为短纤维状，复合材料中同时有大量未完全反应的B4C颗粒存在，所制备钛基复合材料的抗拉强度、硬度较激光熔覆沉积的纯钛有较大幅度的提高。     

原位生成(TiBw+TiCp)/Ti复合材料的高应变速率超塑性

将纯钛粉和B4C粉按一定比例混合均匀后,通过反应热压方法原位合成制备了TiB晶须和TiC颗粒增强体积分数为3%的钛基复合材料,并在950℃以16∶1的挤压比对复合材料进行了高温热挤压变形.采用X射线衍射仪和扫描电镜分别研究了原位生成复合材料的相结构和微观组织,并在700℃以不同应变速率对钛基复合材料进行了高温拉伸变形.研究表明:纯钛和B4C在1200℃真空热压原位合成产生两种不同形状的增强体,即短纤维状TiB晶须和等轴状的TiC颗粒;应变速率为5.95×10-4、1.19×10-3s-1和0.89×10-2s-1时,(TiBw TiCp)/Ti复合材料都表现出超塑性,延伸率分别为205.43%、148.3%和112.85%;700℃变形时(TiBw TiCp)/Ti复合材料的应变速率敏感指数为0.45.     

石墨化度及纤维含量对C/C复合材料性能的影响

以短切高模炭纤维为增强体.制备C/C复合材料,并采用XRD、SEM等方法研究了纤维体积含量和石墨化度对复合材料性能的影响.结果表明:当短切高模炭纤维体积含量小于7%时,随着炭纤维体积含量增加,C/C复合材料的力学性能逐渐升高,高于7%时力学性能降低;随着石墨化度提高,C/C复合材料的力学性能显著降低,短切高模炭纤维增强作用下降;C/C复合材料的石墨化度对电阻率影响大,纤维体积含量对电阻率几乎没有影响;C/C复合材料的石墨化度对材料的抗氧化性影响显著.     

TiB/Ti复合材料自蔓延高温燃烧合成的研究

采用自蔓延高温燃烧合成－准热等静压工艺（SHS／PHIP）制备了TiB-Ti体系复合材料,理论计算了该体系的绝热温度,测量了燃烧温度和燃烧速度。结果表明,绝热温度、燃烧温度和燃烧速度均随Ti含量的增加而降低。对合成产物的分析发现：反应产物主要由TiB和Ti两组组成,TiB相分布均匀,主要有棒状和块状两种形态,并且随Ti含量的增加,TiB尺寸减小;部分产物中还有少量TiB2相存在。合成产物具有高的致密度和硬度,其相对密度超过94％,硬度HRA＞82。     

Microstructure Characteristic of In-situ Ti/TiC Composites

TiC reinforced titanium composites has been produced with different Al content and C content by XDTM. The results have shown that TiC particles are of two different morphologies f coarse dendritical primary TiC and short bar-shape eutectic TiC. Al content has great effects on the morphology of TiC. With the increasing of Al content, the morphology of primary TiC changes from coarse developed dendrite into short bar-shape or plate--shape TiC with 35%Al. Meanwhile, the structure of the matrix changes from single Ti to Ti and Ti2Al and to Ti3Al. However, the C content has no influence on the microstructure of matrix. When the C content is less than 1.2%, the dendrite TiC disappears and only short bar-shape or plate-shape TiC exists in the composites. In addition, the effect of heat of heat treatment on the morphology of TiC has also studied.     

原位合成TiC颗粒增强铁基复合材料的微观结构研究

采用不同化学成分基体制备了原位合成ＴｉＣ颗粒增强铁基复合材料,并以透射电镜为手段对其微观结构进行了分析研究,结果表明,ＴｉＣ增强相周围基体组织与基体含碳量有关,基体中较高的含碳量有助于抑制Ｆｅ２Ｔｉ相的形成,在含钼基体中ＴｉＣ增强相与基体之间存在一富钼的包覆层,进一步改善了基体对碳化钛的润湿性,有利于增强体在基体中的均匀分布。     

TiC/Ti-xY基复合材料的熔铸法制备及微观组织

为了研究钇对TiC/Ti复合材料微观组织的影响,采用熔铸法制备了TiC/Ti-xY复合材料,并利用SEM、X射线衍射、EDS研究了复合材料的微观组织结构、相组成和元素组成,分析了复合材料中TiC的形成过程和微观组织.结果表明:制备的复合材料由钛和碳化钛两相组成,增强相TiC分布较为均匀,初生TiC呈枝晶状,并有含钇细长条共晶TiC析出;增强相TiC与基体界面干净,无反应层;随着钇含量的增加,初生TiC枝晶变得细小,枝晶间距加大,细长条共晶TiC增多.     

Microstructure and mechanical properties of TiC/Ti–6Al–4V composites processed by in situ casting route

Abstract

TiC/Ti–6Al–4V composites containing various volume fractions of TiC were produced by induction skull melting and common casting utilising in situ reaction between titanium and carbon powder. The microstructure and room tensile properties of as cast and heat treated TiC/Ti–6Al–4V composites were investigated. Bar-like or small globular eutectic TiC were found in 5 vol.-%TiC/Ti–6Al–4V composite, whereas the equiaxed or dendritic primary TiC particles were found to be the main reinforcements in 10 and 15 vol.-%TiC/Ti–6Al–4V composites. The as cast TiC/Ti–6Al–4V composites have shown higher strength but lower ductility than those of monolithic Ti–6Al–4V alloy. The shape and fracture of TiC particles can strongly influence the fracture and failure of the composites, and so the ultimate tensile strengths and elongations of as cast composites reduce with the increase in volume fraction of TiC. TiC particles appear to be spheroidised, and titanium precipitation can be found within large TiC particles after heat treatment at 1050°C for 8 h, which can promote the resistance to fracture of composites. Therefore, the elongations of the composites increase significantly, and the ultimate tensile strengths also have marginal increase especially for the 10 and 15 vol.-%TiC/Ti–6Al–4V composites after heat treatment.     

In-situ synthesis of TiC/Fe alloy composites with high strength and hardness by reactive sintering

Fe alloy composites reinforced with in-situ titanium carbide(Ti C) particles were fabricated by reactive sintering using different reactant C/Ti ratios of 0.8,0.9,1 and 1.1 to investigate the microstructure and mechanical properties of in-situ Ti C/Fe alloy composites.The microstructure showed that the in-situ synthesized Ti C particles were spherical with a size of 1–3 μm,irrespective of C/Ti ratio.The stoichiometry of in-situ Ti C increased from 0.85 to 0.88 with increasing C/Ti ratio from 0.8 to 0.9,but remained almost unchanged for C/Ti ratios between 0.9 and 1.1 due to the same driving force for carbon diffusion in Ti Cxat the common sintering temperature.The in-situ Ti C/Fe alloy composite with C/Ti = 0.9 showed improved mechanical properties compared with other C/Ti ratios because the presence of excess carbon(C/Ti = 1 and 1.1) resulted in unreacted carbon within the Fe alloy matrix,while insufficient carbon(C/Ti = 0.8)caused the depletion of carbon from the Fe alloy matrix,leading to a significant decrease in hardness.This study presents that the maximized hardness and superior strength of in-situ Ti C/Fe alloy composites can be achieved by microstructure control and stoichiometric analysis of the in-situ synthesized Ti C particles,while maintaining the ductility of the composites,compared to those of the unreinforced Fe alloy.Therefore,we anticipate that the in-situ synthesized Ti C/Fe alloy composites with enhanced mechanical properties have great potential in cutting tool,mold and roller material applications.     

Microstructure of XDTM Ti-6Al/TiC composites

XD^TM method has been used to prepare TiC particles reinforced titanium composites. The phases constitute and microstructure of the Ti-6Al/TiC composites have been investigated by XRD and SEM. The lattice parameter value of TiC calculated from the XRD pattern has indicated that there exists carbon deficiency in TiC. The microstructure observed by SEM has shown that TiC is of dendritical and spherical morphology, which quite different from that of the TiC in Al/TiC master alloy. In macrostructure, the TiC particles homogeneously distribute in the matrix, but the spherical TiC mainly segregate at the grain boundary, especially at the triangle grain boundary. Microstructure of the interface has also been observed by TEM and HTEM. No reaction product has been found in the interface, but a C atom diffusion layer was determined by energy spectrum diffraction and observed by HREM image of interface microstructure. Although no definite crystallographic relationship can be defined, a orientation relationship of [0110]_Ti//[011]_TiC has been obtained.     

原位自生Ti3 Al金属间化合物基复合材料的微观结构

采用原位自生（XD）法制备Ti3Al金属间化合物基复合材料,对复合材料的XRD,OM和SEM的分析结果表明,Ti-17Al-0.5C复合材料的基体为Ti3Al,增强相为Ti3AlC,且增强相在基体中按一定的方位排列,Ti-17Al-1.5(2.0)C复合材料的基体为Ti3Al,增强相由心部TiC矣包覆层Ti3AlC双层组成,随着含C量的增加,增强相由不发达的树脂晶变为等轴晶,对合金进行微力学探针测试表明,增强相TiC和Ti3AlC的显微硬度和弹性模量均大于基体Ti3Al,随着C含量的增加,合金中增强相和基体的显微硬度和弹性模量无明显变化。     

异构结构纳米金刚石/钛基复合材料的微观组织与力学性能

目的 探究不同粗细晶比例的异构结构对纳米金刚石/钛基复合材料的物相组成、组织结构及力学性能的影响.方法 首先利用低能与高能球磨机进行粉末混合,接着利用放电等离子烧结技术对复合材料进行制备,最后采用金相显微镜、XRD、SEM、TEM、显微硬度计、材料力学电子万能试验机对复合材料的形貌、成分及力学性能进行分析.结果 复合材料中有纳米TiC相形成,微观组织中形成了细/粗晶的异构结构和增强相的成分浓度梯度分布;随着细晶比例的逐渐增加,硬度和强度都逐渐增强,硬度最高可达382HV,拉伸屈服强度最高可达1017 MPa,塑性为17.8％.结论 添加的增强相纳米金刚石和异构结构的设计,使复合材料的硬度、强度得到了显著提高,而塑性损失很小.异构结构的钛基复合材料具有优异的强度和塑性的组合.强韧化机理为可控非均匀分布的纳米金刚石和TiC增强相对位错运动的阻碍和钉扎机制.     

B添加对TiC/Ti6Al4V复合材料组织和耐磨性能的影响

用熔铸法制备原位自生钛合金基复合材料,研究B元素的添加对TiC/Ti6Al4V复合材料显微组织和耐磨性能的影响.结果表明:当B的加入量小于0.06%(质量分数,下同)时,随B加入量的增加,复合材料中的枝晶状增强相TiC的尺寸显著减小,由粗大的树枝状逐渐减小为细小的树枝状,甚至链条状和颗粒状,但是复合材料的耐磨性下降;当B添加量从0.1%增加到0.6%时,枝晶状TiC细化不明显,TiC周围伴有纤维状的TiB出现,复合材料的耐磨性能得到明显提高.B对TiC枝晶的细化是凝固前沿成分过冷区形核率的提高和TiC生长率降低的综合作用结果.耐磨性能的改善主要是生成的大量纤维状TiB共同参与了磨损所致.