Self-Propagating High-Temperature Reductive Synthesis of TiB_2-Al_2O_3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis(SHS) method with reductive process from B2O3-TiO2-Al system. X-ray diffraction(XRD) and scanning electron microscopy(SEM) analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Combustion Synthesis and Densification of NiAl/TiB_2 Composites

A suitable combustion synthesis and densification process was designed to fabricate dense NiAl/ TiB2 composites from Ni-Al- Ti-B system. Combustion synthesis processing and microstructure characteristics of products were studied in detail. The results show that the amount of TiB2 ceramics has a great influence on the combustion synthesis processing and microstructure; with the increase of the amount of TiB2 ceramics, the combustion temperature and combustion velocity increase rapidly. The volume of synthesized products and the grain size of ceramics particle size are also affected by the amount of TiB2 ceramics. TiB2 ceramics fiber can be produced in this synthesis system. The dense NiAl/ TiB2 composites with residual porosity of no more than 1% are fabricated by the combustion synthesis and hot pressing, the mechanical properties of the dense NiAl/ TiB2 composites increase with increase of the amount of TiB2 ceramics.     

激光熔覆钛基复合涂层的显微组织和硬度分析

采用激光熔覆快速非平衡合成方法制备了原位反应合成TiB增强钛基复合材料.用Y2O3、Ti和B的混合粉末在Ti-6Al-4V基体表面激光熔覆制得TiB/Ti复合涂层.采用X线衍射仪(XRD)、扫描电子显微镜(SEM)、能量散射光谱仪(EDS)和硬度测试等方法,研究了原位合成TiB/Ti复合涂层的显微结构和显微硬度.结果显示:激光熔覆层的相结构主要为α-Ti和TiB两相,TiB增强相均匀地分布于复合涂层中,熔覆层的硬度值高于基体Ti合金的硬度值1倍以上,Y2O3含量(质量分数w,全文同)为1％的激光熔覆涂层内部的增强相组织最为均匀、细小,且硬度值也最高,平均硬度(HV)值约为830.     

B4C／TiO2／Al复合材料制备及其性能

采用热压法制备了B4C／TiO2／Al复合陶瓷材料，试验结果表明，TiO2和Al的加入，使得B4C／TiO2／Al复合材料的硬度、抗弯强度和断裂韧性比纯B4C陶瓷材料有较大程度的提高；而且，添加相促进了复合材料的烧结．利用热力学和X射线衍射分析研究烧结过程中的化学反应，分析结果表明，复合材料中没有发现TiO2，Al，Al2O3;同时在复合材料中出现了TiB2，因为在热压过程中TiO2-B4C反应生成TiB2．分析了B4C／TiO2／Al复合陶瓷材料的微观结构和增韧机理．     

TiB_2-xFe体系SHS合成的热力学计算与实验

对ＳＨＳ法制备ＴｉＢ２－ｘＦｅ系统复合材料进行了热力学计算，得到了绝热燃烧温度同金属稀释剂含量、绝热燃烧温度同反应预热温度等关系。依据热力学计算的结果对ＳＨＳ合成ＴｉＢ２－ｘＦｅ系统的过程机理进行了预测，并运用实验结果加以验证。     

Solidification Behavior of in situ TiB_2/Cu Composite Powders during Reactive Gas Atomization

2wt% TiB_2/Cu composite powders were fabricated in situ by reactive gas atomization.The fabricated composite powder exhibits high sphericity,and the powder sizes range from 5 μm to 150 μm.The morphology of the Cu matrix and the distribution of the TiB_2 particles in the composite powders vary with the powder size.The critical transitions of interface morphologies from dendritic-to-cellular and cellular-to-planar interfaces occurs when the composite powder sizes decrease to 34 μm and 14 μm,respectively.Compared with pure Cu droplets,the composite droplets undergo critical transition of the interface morphologies at a smaller droplet size corresponding to a higher cooling rate because the existence of TiB_2 particles can cause instability in the advancing solidification front and heterogeneous nucleation.With decreasing powder size,the extent of the TiB_2 particle interdendritic segregation decreases as the result of enhanced engulfment of TiB_2 particles by the advancing solidification front.     

Synthesis of Ti3SiC2/TiB2 Composite by In-situ Hot Pressing (HP) Method

Ti3SiC2/TiB2 composite was successfully obtained by hot pressing Ti/TiC/Si/B4C power mixtures.Volume fraction of TiB2 in Ti3SiC2/TiB2 composite can not exceed 10%.Incorporation of excessive TiB2 will affect the reactions process.TiC and Ti5Si3 were two important intermediate phases during the whole reactions.The microstructure characteristics of the Ti3SiC2/TiB2 composites were analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The experimental results show that the grains of Ti3SiC2/TiB2 composite are structured in a layered form,and the formation of TiB2 particles as reinforcements with elongated or equiaxed shape distributes in Ti3SiC2 matrix.     

Fabrication and Microstructure of BN Matrix Composites with Electrical COnductivity

BN ceramic is advanced engineering ceramics with excellent thermal shock resistance,good workability and excellent dielectricity.TiB2 ceramic has excellent electric conductivity,high melting points,and corrosion resistance to molten metal.Therefore,the composite consisting of BN and TiB2 ceramics is expected to have a combination of above-mentionaed properties,thereby can be used as self-heating crucible.In this puper,hot pressing technology was used to fabricate the high performance BN-TiB2 composite materials,microstructure and electric conducting mechanism were studied,and the relationship between the microstructure and physical property was discussed.the results show that the microstructure of composites has a great influence on the physical property of composites.The BN-TiB2 composites with excellent mechanical strength and stable resistivity can be obtained by optimizing the processing parameter and controlling the microstructure of composites.     

WCoB金属陶瓷的制备及其性能研究

以WC、TiB2、Co粉末为原料,采用真空液相反应烧结技术制备WCoB金属陶瓷,并利用XRD、SEM和EDS对其微观形貌及相组成进行了表征。结果表明,WCoB金属陶瓷由WCoB、W2CoB2、TiC、Co2B和TiB2等相组成,其硬度为HRA84.4～92.2,合金密度为9.3～10.2g/cm3。随着钴含量的增加,烧结后WCoB金属陶瓷的合金密度和硬度值均有所下降,较高的烧结温度有利于晶粒细化。磨损试验发现WCoB金属陶瓷的耐磨性优于YG8硬质合金。     

Graded Materials of (TiB_2)_pNi with Nickel Substrate Prepared by Field-Activated Pressure-Assisted Synthesis Process

The preparation of functionally graded materials (FGMs) of (TiB2)pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process (FAPAS) was investigated. Ni3Al was chosen as a layer of FGM for the first time due to its great deal of heat released during its synthesis from nickel and aluminium powder. The microstructure, phase composition of layers, micro-hardness and elemental concentration profiles across interfaces were characterize...     

自蔓延高温合成法（SHS）制备致密的Al_2O_3－TiC陶瓷

采用电热爆－加压法（ＥＴＥ－Ｐ）和燃烧合成制粉＋加压法（ＳＨＳ＋ＨＰ）制备了致密的Ａｌ２Ｏ３陶瓷．研究表明，ＳＨＳＡｌ２Ｏ３－ＴｉＣ陶瓷的力学性能和切削性能均优于采用传统热压方法所制备的Ａｌ２Ｏ３＋ＴｉＣ陶瓷刀具，并对ＳＨＳＡｌ２Ｏ３＋ＴｉＣ的的显微结构及致密化机制作了研究．     

Self-Propagating High-Temperature Reduetive Synthesis of TiB2-Al2O3 Composite Powders

TiB2-Al2O3 composite powders were produced by self-propagating high-temperature synthesis（SHS） method with reductive process from B2O3-TiO2-AI system. X-ray diffraction（XRD） and scanning electron microscopy（SEM） analyses show the presence of TiB2 and Al2O3 only in the composite powders produced by SHS. The powders are uniform and free-agglomerate. Transmission electron microscopy （TEM） and high resolution electron microscopy （HREM） observation of microstructure of the composite powders indicate that the interfaces of the TiB2-Al2O3 bond well, without any interfacial reaction products. It is proposed that the good interfacial bonding of the composite powders can be resulted from the TiB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

TiC-Fe复合材料涂层自蔓延工艺研究

利用自蔓延高温燃烧合成结合准热等静压同时致密化技术,以Ti-C-Fe为原料,在Q235钢表面制备耐磨、耐高温TiC-Fe陶瓷涂层,并对涂层进行抗弯曲、耐烧蚀及耐磨性能的检测.结果表明:钢基表面涂层中TiC呈颗粒状均匀分布,组织致密,与基体结合良好,且涂层具有优良的抗弯曲、抗烧蚀及耐磨损性能.     

TiB2/Cu复合材料组织与性能的研究

以Ti、B和Cu的单质粉末为原料,经混粉-冷压成形-真空烧结,制备出原位自生TiB2陶瓷颗粒增强铜基复合材料.并借助热分析方法和X射线衍射对增强颗粒进行分析,同时通过扫描电子显微镜对复合材料组织进行观察,进一步测定复合材料的力学性能.结果表明,在Ti-B-Cu体系中,通过原位反应生成增强相是TiB2.随着B粉和Ti粉含...     

一种原位TiB_2颗粒增强铝基复合材料的制备及特性

以Al-6Cu-0.2Mg-1Mn合金为基体,采用混合盐原位反应法制备不同TiB2颗粒含量（质量分数分别为1%、3%、5%）的颗粒增强铝基复合材料,对不同处理状态的TiB2颗粒增强复合材料及Al-6Cu-0.2Mg-1Mn合金的相结构与显微组织进行分析,并测试其维氏硬度。结果表明,原位反应生成的TiB2颗粒能改善基体组织,阻止基体晶粒生长的方向性,得到等轴晶;随着增强相TiB2颗粒含量的增加,基体组织得到明显细化;不同处理状态3%及5%含量TiB2颗粒增强复合材料的维氏硬度均显著高于相应Al-6Cu-0.2Mg-1Mn合金的维氏硬度。     

自蔓延高温合成法制备TiN陶瓷粉末

采用自蔓延高温合成法（ＳＨＳ）制备了ＴｉＮ陶瓷粉末，研究了压坯密度，稀降剂掺加及氮气分压对合成过程和合成转化率的影响．结果表明：采用ＳＨＳ法制备的ＴｉＮ是由ＴｉＮ及少量Ｔｉ的固溶体构成的，通过改变工艺参数，可以得到高纯度的ＴｉＮ．影响ＴｉＮ转化率的关键因素是Ｔｉ粉与氮气的有效接触面积和氮气向反应区的转输速度．     

Ti—C—Fe体系的自蔓延高温合成

采用自蔓延高温合成技术制备ＴｉＣ／Ｆｅ复合粉末材料，研究了铁含量对燃烧温度，燃烧波速度的影响。采用ＸＲＤ和ＳＥＭ对合成产物的物相和结构特征进行了研究，并认相量对控制材料的结构特征起着主要的作用。通过燃烧波铜楔块淬熄法，对合成过程及结构形成过程作了分析。     

TiC陶瓷滤片的制备及其性能研究

在对TiC陶瓷的性能及其制备工艺进行分析研究的基础上,利用SHS/PHIP技术制备了致密的TiC-TiB2复相陶瓷材料,并对材料进行切割加工成型和清洗,得到和所需滤片形状相同的TiC-TiB2复相陶瓷片,然后再根据TiC和TiB2化学性能的差异,用王水的强腐蚀性溶解其中的TiB2陶瓷相从而得到孔隙大小均匀的、性能优异的TiC陶瓷滤片.用该方法制备的TiC陶瓷滤片,孔隙的直径范围在2~3μm,分布均匀,可以在任何性质的液体中使用,也可用于熔融金属液的过滤.     

A New Process for Preparing Fine-ceramic-containing Composite Coatings--Flame Spray Synthesis

Flame spray synthesis (FSS), a combination of the flame spray technology and Self-propagation High-temperature Synthesis (SHS) was developed for preparing fine-ceramic-containing composite coatings. It can simplify the preparations of powder to synthesize and deposit the desired materials in one step. The preliminary results obtained from TiC-Fe cermet coatings by FSS process are reported. The peculiar microstructure of the composite coatings, which contains very fine (<1m) and round TiC and alternate TiC-rich (Hv=11?13GPa) and TiC-poor layers (Hv=3.0 -6.0GPa), is expected to play an important role in their tribological properties.     

Microstructural evolution of titanium matrix composite coatings reinforced by in situ synthesized TiB and TiC by laser cladding

Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles were successfully fabricated on Ti6Al4V by laser cladding using Ti-B_4C-Al or Ti-B_4C-C-Al powders as the precursor materials.The microstructural and metallographic analyses were made by X-ray diffraction(XRD),optical microscope(OM),scanning electron microscopy(SEM),and electron probe microanalysis (EPMA).The results show that the coatings are mainly composed ofα-Ti cellular dendrites and a eutectic transformation p...