(GNPs+B)/TC4复合材料组织和硬度研究

采用放电等离子烧结技术(SPS),制备石墨烯纳米片(GNPs)、硼粉(B)增强TC4钛基复合材料(TiMCs).利用扫描电镜、拉曼光谱对混合粉末以及烧结后材料的组织进行了研究.利用维氏硬度仪对复合材料进行硬度测试.结果表明:GNPs和B与基体原位反应生成TiC颗粒(TiCp)和TiB晶须(TiBw)构成的非连续网状结构...     

Al含量对Ti—B体系自蔓燃高温合成过程的影响

采用纯Ti粉、Al粉及B粉进行整体加热，使其发生自蔓燃高温反应，在Al基中合成TiB2粉末。研究了Al含量及合成温度对Ti-Al-B体系反应产物微观结构的影响，探讨了在Al基体中TiB2粒子的形成机理。研究结果表明，在Ti-Al-B体系中，800℃左右Ti－B就可反应合成TiB2，这与Ti－Al之间发生的放热反应有关，Al的存在缓和了TiB2的合成反应；在Al基中成功地制备出了细小、均匀的、粒度可控的TiB2粒子。TiB2的粒度约为0．5～5、0μm，主要取决于反应物中Al的含量。     

TiB_2晶须的自蔓延高温合成及其生长机理

以Mg、B2O3、TiO2为原料,Cu2O为添加剂,采用自蔓延高温合成法制备TiB2粉体。研究添加剂Cu2O含量对TiB2晶体形态的影响,讨论TiB2晶须的生长机理。采用XRD、SEM分析合成产物的物相组成及微观形貌。结果表明:加入4%的Cu2O可生成大量高长径比的TiB2晶须,TiB2晶须的生长机制属于气-液-固(V-L-S)机制;首先Cu2O在高温下分解生成O2和Cu,O2向外喷射时形成的孔道为TiB2晶须的生长提供空间条件,自蔓延反应产生的高温为其提供能量条件,熔融态的Cu作为催化剂,与Ti形成以反应生成的TiB2为衬底的合金液滴,然后通过不断吸收Ti原子和B原子,使TiB2形核并定向生长,最终形成TiB2晶须。     

一种原位自生钛镍合金骨架增强钛基复合材料的制备方法

本发明公开了一种原位自生钛镍合金骨架增强钛基复合材料的制备方法,具体工艺如下:(1)将球形钛粉酸洗、清洗后干燥;(2)将镍粉加入到去离子水中清洗后干燥;(3)将经干燥后的球形钛粉与经干燥后的镍粉球磨混匀,得到镍颗粒包覆钛粉;(4)将镍颗粒包覆钛粉进行热压烧结,经冷却后得到原位自生钛镍合金骨架增强钛基复合材料。采用球磨工艺制备镍颗粒包覆钛粉,然后经热压烧结使镍颗粒与钛基粉末发生固溶反应,通过控制热压烧结的升温速率和保温时间控制镍元素向钛基体内部的扩散速率,从而调节钛镍合金的生长尺寸,并在钛合金基体内部形成纳米棒状的钛镍合金骨架,起到强化作用,最终提高钛基复合材料的力学性能。     

电触头用TiB2颗粒增强/Cu基复合材料组织与性能分析北大核心

采用热压烧结方法制备电触头用TiB2颗粒增强/Cu基复合材料,通过XRD、OM、SEM等测试手段研究不同TiB2颗粒含量对其组织和性能的影响。研究结果表明:复合材料生成了强度很高的Cu衍射峰,Cu基体内已经形成由TiB2与TiB共同构成的混杂增强相。所有复合材料试样中的增强相都形成了均匀分布形态,TiB2颗粒含量6%的试样含有颗粒与晶须两种增强相。当TiB2颗粒含量的比例上升后,所有Cu基复合材料试样的硬度都发生了增大的现象,而密度发生了减小,导电率增加。TiB2(6%)/Cu复合材料试样在DSC升温过程中形成了4个特征峰。当温度到达800℃时形成了Cu3Ti金属间化合物;随着温度上升到1100℃后,试样基体内开始同时生成TiB2颗粒与Ti B晶须。     

原位自生TiB2p/Al-18%Si复合材料的组织和性能

采用TiO2和KBF4粉体为反应物,适量Na3AlF6为覆盖剂,用熔体直接反应法制备了TiB2p/Al-18%Si复合材料,通过OM、SEM和EPMA对复合材料的相及微观组织进行研究,并测试了常温条件下复合材料的硬度、抗拉强度和干滑动摩擦磨损性能。结果表明,原位反应生成的TiB2颗粒尺寸小于1μm,且大多数在Al-18%Si合金基体中均匀分布,粗大的α-Al枝晶和针状共晶Si组织得到细化;复合材料的硬度、抗拉强度、摩擦磨损性能高于无TiB2颗粒的Al-18%Si合金。     

反应钎涂碳化物/铁基自熔合金复合涂层及组织形成机理

利用工业原料纯铁粉、硅粉、钛铁粉、硼铁粉、铬铁粉、胶体石墨以及镍粉，真空条件下通过反应钎涂于1200℃在低碳钢基体上制备了白色、表阿光滑、平整且与基体为冶金结合的碳化物／铁基合金复合涂层。采用扫描电子显微镜、能谱仪、X射线衍射仪及硬度计，研究了涂层的相组成、组织结构和成分分布。结果表明：涂层为复合结构，不存在分层现象，其组织由粘结相γ-Fe固溶体，以及α-Fe（马氏体）、（Fe，Cr）7G3相和TiC相构成。涂层中通过反应原位合成的（Fe，Cr）7C3和TiC形状不同，（Fe，Cr）7C3的形状大部分为针状，而TiC形状为颗粒状，且主要分布在先前的钛铁粉颗粒轮廓之内。该复合涂层表面硬度高达73．9HR30N以上。     

烧结温度对10TiB/Ti-4.5Al-6.8Mo-1.5Fe复合材料组织与性能的影响

以Ti、Al、Mo、Fe元素粉末及LaB6和TiB2粉末为原料,采用机械混合法制备钛基复合粉末,经高速压制成形后,分别在1 150、1 250和1 350℃下真空烧结制备以TiB晶须为增强体、钛合金Ti-4.5Al-6.8Mo-1.5Fe为基体的钛基复合材料。借助X射线衍射、金相显微镜和扫描电镜分析材料的物相组成和微观组织,测试复合材料的维氏硬度(HV2.0)和拉伸性能,研究烧结温度对复合材料的组织和力学性能的影响。结果表明:10TiB/Ti-4.5Al-6.8Mo-1.5Fe复合材料的相对密度随烧结温度升高而增加,烧结温度为1 350℃时达到最大值98.9%;TiB晶须的长径比随烧结温度升高显著降低。烧结温度为1 250℃时,该材料的维氏硬度和室温抗拉强度都达到最大值,分别为399HV和1 179 MPa。     

绝热燃烧温度对TiC-TiB2复合陶瓷物相及组织的影响

以B4C粉、Ti粉、CrO3粉以及Al粉为原料,采用超重力下自挤压辅助燃烧合成技术,以快速凝固方式制备出不同绝热燃烧温度的TiC-TiB2复合陶瓷.XRD、FESEM与EDS结果表明,TiC-TiB2复合陶瓷基体主要由片状的TiB2晶粒构成,同时在TiB2基体间还分布着少量不规则的TiC,(Ti,Cr,Al)C1-x及Al2O3残余夹杂物.随着绝热燃烧温度的升高,Al2O3的含量先减少后增加,(Ti,Cr,Al) C1-x的含量逐渐增加,TiB2与TiC的含量基本不变.     

真空碳热还原法制备高纯TiB2粉末

在对碳热还原反应TiO2＋B2O3＋5C→TiB2＋5CO↑进行热力学计算的基础上，采用真空碳热还原TiO2和B2O3的方法，制备出了纯度达99．34％的TiB2粉末。研究结果表明：采用真空碳热还原法制取TiB2粉末可降低实际反应温度200℃左右；真空环境是保证获得高纯TiB2粉末的重要条件IC还原剂的适当过量能显著提高产物TiB2的纯度。     

Synthesis of ductile titanium-titanium boride (Ti-TiB) composites with a beta-titanium matrix: The nature of TiB formation and composite properties

The study focused on the in-situ synthesis of titanium (Ti)-titanium boride (TiB) composites with β phase in the matrix by reaction sintering of TiB₂ with Ti and alloying element powders. The goal was to examine the nature of TiB whisker formation in three different kinds of powder mixtures: (1) β-Ti alloy powders and TiB₂; (2) α-Ti powder, a master alloy (Fe-Mo) powder containing the β-stabilizing elements, and TiB₂; and (3) α-Ti powder, a β-stabilizing elemental powder (Mo or Nb), and TiB₂. The effects of powder packing and the relative locations of powder particles on the morphological changes in TiB whisker formation and their growth were studied at processing temperatures ranging from 1100°C to 1300°C. The morphology, size, and distribution of whiskers were found to be influenced by the powder-packing conditions. A large particle-size ratio in bimodally packed mixtures led to the formation of a TiB monolithic layer around β grains. With a relatively finer starting powder, smaller size ratio, and trimodal packing arrangement, the TiB whiskers were found to be distributed more homogeneously in the matrix. The study also used the X-ray direct comparison method and the structure factor for the β phase to determine the volume fraction of TiB phase from X-ray data. Tensile tests and fractographic investigations were carried out on selected composites. The evolution of the composite microstructure, the influence of powder-packing variables, and the morphology and growth of TiB whiskers and their effect on mechanical properties are discussed.     

稀土元素的添加对原位生成的Ti-TiC-TiB复合材料抗磨损性能的影响

采用Ti 6Al 4V 5B4C和Ti 6Al 4V 5B4C 1Nd 两种成分的原始粉末, 反应热压后原位生成了Ti TiC TiB复合材料。经过X射线检测, 证明了试验中原位生成反应5Ti+B4C 4TiB+TiC的进行。采用摩擦磨损试验机检测了两种材料的抗磨损性能。通过扫描电子显微镜和电子探针分析了材料的磨损表面。结果表明, 添加稀土元素能提高材料的硬度, 韧性和抗磨损性能。     

原位反应制备Ag/TiB2复合材料

在Ti和B粉末原位反应生成TiB2条件热力学分析的基础上,采用机械合金化和粉末冶金原位合成工艺制备Ag/TiB2复合材料.采用Ag粉,Ti粉和B粉作为材料,按照Ti和B摩尔比1∶2占复合材料质量分数分别为0.5％,1.0％,3.0％和5.0％ TiB2进行配料,混合后在自制高能球磨机上球磨60h,转速为150 r·min-1,球料比为60∶1.球磨后的粉末在压力机上用模具冷压成型φ21 mm ×5 mm的块状试样,压力600 MPa,保压30 s.最后将混合粉末的压制体在900℃保温4h热压炉中进行原位反应,并通入Ar气作为保护气氛,制备了不同TiB2含量的新型Ag/TiB2复合材料,系统研究了TiB2含量对AgTiB2触头复合材料组织和性能的影响.通过X-ray衍射仪,扫描电子显微镜(SEM)和能谱仪(EDS)表征分析了Ag/TiB2复合材料的相组成及显微组织,并采用维式硬度计和涡流电导仪对硬度和导电率进行了测试.研究结果表明,采用机械合金化球磨和原位反应粉末冶金技术制备Ag/TiB2复合材料是可行的.随着TiB2含量的增加,Ag/TiB2复合材料出现明显的TiB2团聚现象,且Ag/TiB2复合材料的硬度呈现先增大后减小的趋势,在硬度值为3％时,达到最大硬度值87.1 HV,但Ag/TiB2复合材料电导率随着TiB2含量的增加逐渐下降.     

Reaction Synthesis of Titanium Matrix Composites Through Powder Metallurgy Processing Technique

Titanium matrix composites reinforced with 10, 20 and 30 vol.% of in situ TiB–TiC reinforcements were fabricated using powder metallurgy method which offers economical solution for production of high performance materials. The in situ composites were produced by reaction of sintering of uniformly blended and compacted powders of titanium and boron carbide in required proportions. XRD analysis confirmed the completion of in situ reaction. SEM studies confirmed uniform distribution and the shape of the reinforcement, TiB as whiskers and TiC as equiaxed particles. The effect of morphology and reinforcement volume on properties of the composites were evaluated by measurement of modulus, hardness, three-point bend test and compression test at ambient temperature along with unreinforced titanium. The study has revealed that the composites with increasing percentage of the reinforcements exhibited improved properties due to the presence of TiB whiskers distributed uniformly. Fractography of the three-point bend tested samples revealed the plastic mode of fracture for unreinforced titanium and the composites exhibiting mixed mode of fracture.     

Fatigue and fracture of damage-tolerant In Situ titanium matrix composites

In an effort to engineer damage-tolerant ingot metallurgy (IM) in situ titanium matrix composites with attractive mechanical properties, the fatigue and fracture properties of a range of high-modulus titanium alloys reinforced with TiB whiskers were examined. The strengthening effects due to elastic whisker reinforcement are quantified using shear lag and rule-of-mixture models. The effects of alloy composition and microstructure on the fatigue behavior of the in situ titanium composites will also be discussed.     

Titanium-titanium boride (Ti-TiB) functionally graded materials through reaction sintering: Synthesis,microstructure, and properties

The study demonstrates an effective method to synthesize titanium-titanium boride (Ti-TiB) functionally graded material (FGM) tiles by exploiting the simultaneous TiB whisker formation in situ and the densification occurring during the reaction sintering process. The macrostructure of the graded material was designed to have a beta-titanium (β-Ti) layer on one side with the composite layers of Ti-TiB mixture having increasing volume fraction of the TiB through the thickness. The approach used an optimized tri-modal powder mixture consisting of α-Ti powder, a master alloy of the β-stabilizing-element powders (Fe-Mo), and TiB₂. The structure and properties of both of these FGMs were systematically characterized by X-ray diffraction, electron microscopy, and microhardness measurements. Interestingly, it has been found that two different kinds of TiB whisker morphologies were observed in the FGMs. The Ti-rich layers were found to have large and pristine TiB whiskers uniformly distributed in the Ti matrix. On the other hand, the TiB-rich layer was found to have a network of interconnected and relatively smaller TiB whiskers appearing as clusters. The layers of intermediate TiB volume fractions were found to consist of both the morphologies of TiB. The effectiveness of the X-ray direct comparison method for the determination of volume fractions of phases in the FGM layers was also demonstrated. The Vickers microhardness level was found to increase dramatically from 420 kgf/mm² in the β-Ti layer to 1600 kgf/mm² in the TiB-rich layer. The elastic residual stresses retained in the graded layers after fabrication were determined based on an elastic multilayer model. The nature of microstructure, the hardness variation, and the distribution of residual stresses in these novel FGMs are discussed.     

The Effect of TiB2 Content on Wear and Mechanical Behavior of AZ91 Magnesium Matrix Composites Produced by Powder Metallurgy

Powder Metallurgy and Metal Ceramics - In this research, AZ91 magnesium matrix composites reinforced with three weight fractions (10, 20, and 30 wt.%) of TiB2 particulates were fabricated by powder...     

Microstructural characterisation and mechanical properties of spark plasma-sintered TiB2-reinforced titanium matrix composite

Titanium and titanium matrix composites, reinforced with TiB₂ particles, have been synthesised by the spark plasma sintering method at 1050°C under 50?MPa pressure, using mixtures of 2.4?wt.-% TiB₂ and 97.6?wt.-% Ti powders. The changes in microstructural features and mechanical properties were investigated. XRD results and SEM observations confirm the formation of TiB whiskers as a result of the reaction between Ti and TiB₂. However, some unreacted TiB₂ particles have remained in the composite owing to the incomplete chemical reaction between matrix and additives. The measured mechanical properties demonstrate that the increase in hardness and tensile strength with TiB₂ addition is mainly attributed to the generation of TiB whiskers, increase in relative density and decrease in grain size, while the reduction in bending strength is possibly due to the plastic restraint imposed on the matrix by the TiB whiskers and unreacted TiB₂ particles.     

Synthesis of TiC–NiCrBSi Binder Alloy Composite Powders for Cladding and Deposition of Wear-Resistant Coatings

Russian Journal of Non-Ferrous Metals - TiC–NiCrBSi binder metal matrix composites are fabricated by self-propagating high-temperature synthesis (SHS) in reaction powder mixtures of titanium,...