电弧熔炼Ti6Al4V/B4C复合材料微观组织与力学性能

采用真空电弧熔炼技术制备了不同含量B₄C的Ti6Al4V/B₄C钛基复合材料,并采用光学显微镜、扫描电子显微镜、显微硬度计、静态压缩及拉伸测试等对其微观组织及力学性能进行了表征分析. 结果表明,电弧熔炼过程B₄C与钛基体原位反应生成TiB,TiC及TiB₂相,TiB呈现一维生长晶须状,TiC呈现颗粒状,在B₄C质量分数为10%时生成块状TiB₂,并可能会形成特殊的中空棱柱状结构Ti(B_xC_y)聚合物. 原位反应生成的TiB₂可显著提高钛基复合材料的显微硬度. 当B₄C质量分数为0.5%时,钛基复合材料原位反应生成的连续网状、均匀分布的TiB和TiC试样具有最优力学性能,试样最大抗压强度值达到1 990 MPa,最大压缩应变为35.5%,压缩性能超过熔炼钛合金,抗拉强度达到1 034 MPa,与熔炼钛合金材料相比提高近24%,但塑性有所降低,并随着B₄C含量增加,抗拉强度逐渐下降,其断裂方式由韧性断裂转变为脆性断裂.     

Ti6Al4V合金表面氩弧熔覆原位合成TiC-TiB2增强钛基复合涂层组织与耐磨性

以B4C和Ni60A粉末为预涂材料,采用氩弧熔覆技术,在Ti6Al4V合金表面原位合成TiC与TiB₂增强相增强钛基复合材料涂层.运用XRD,SEM等分析手段研究了复合涂层的显微组织,利用显微硬度仪测试了复合涂层的显微硬度并用磨损试验机分析了其在室温干滑动磨损条件下的耐磨性能.结果表明,熔覆层组织主要由TiC和TiB₂组成,TiC颗粒和TiB₂颗粒弥散分布在基体上,TiC颗粒的尺寸为2~3μm,而呈长条状的TiB₂颗粒尺寸为3~5μm.显微硬度和耐磨性测试结果表明,该复合涂层显微维氏硬度高达1200MPa左右,复合涂层的耐磨性能比Ti6Al4V基体提高约20倍.     

不同TiN含量整体式PCBN复合材料微观组织及性能研究

在高温高压烧结条件下以TiN为主要结合剂,加入一定量的Al,研究TiN含量对整体聚晶立方氮化硼(PCBN)复合材料微观组织与力学性能的影响。分别对烧结样品进行物相组成分析、微观结构观测以及体积密度和硬度测试。结果表明:CBN与结合剂TiN、Al反应生成TiB₂、AlN,TiN与Al发生反应生成Al₃Ti ,TiN与反应生成物AlN、TiB₂、Al₃Ti等构成黏结相均匀分布于 CBN晶界周围,牢固地将CBN 晶粒黏结在一起,有效地提高了整体PCBN复合材料的结合强度。低含量TiN对整体PCBN的致密度和硬度均有一定程度的提升,在TiN、Al、CBN的质量分数分别为10%、10%、80%时,整体PCBN复合材料的力学性能达到最佳。      

Laser Powder Deposition Parametric Optimization and Property Development for Ti-6Al-4V Alloy

In this study, Ti6Al4V alloy was produced via laser powder deposition (LPD). To obtain Ti6Al4V alloy with maximum density, LPD parameters for preparing Ti6Al4V samples were optimized using the Taguchi method. Results were analyzed on the basis of the signal-to-noise (S/N) ratios and analyses of variance. A high energy density should be used to achieve higher levels of densification. The optimal combination of parameters for density was a scanning speed of 550 mm/min, laser power of 160 W, powder feeding rate of 0.99 g/min, and shield gas flow of 8 L/min. An almost fully dense Ti6Al4V sample was prepared using the optimized LPD process, and the relative density was greater than 99%. In addition, the microstructure and properties of Ti6Al4V samples prepared by optimized LPD process were investigated. The microstructure investigation revealed that the LPD-prepared Ti6Al4V sample was predominantly composed of fine acicular α phase and lath-type α phase. Tensile and microhardness tests indicated that the LPD sample had higher mechanical properties than the traditional cast Ti6Al4V alloy because of the acicular martensitic phase and smaller grain size.     

Effects of Forming Conditions and TiC–TiB_2 Contents on the Microstructures of Self-Propagating High-Temperature Synthesized NiAl–TiC–TiB_2 Composites

The NiAl–TiC–TiB2 composites were processed by self-propagating high-temperature synthesis(SHS) method using raw powders of Ni, Al, Ti, B4 C, TiC, and TiB2, and their microstructure and micro-hardness were investigated. The TiC–TiB2 in NiAl matrix, with contents from 10 to 30 wt%, emerged with the use of two methods: in situ formed and externally added. The results show that all final products are composed of three phases of NiAl, TiC, and TiB2. The microstructures of NiAl–TiC–TiB2 composites with in situ-formed TiC and TiB2 are fine, and all the three phases are distributed uniformly. The grains of NiAl matrix in the composites have been greatly refined, and the micro-hardness of NiAl increases from 381 HV100 to 779 HV100. However, the microstructures of NiAl–TiC–TiB2 composites with externally added TiC and TiB2 are coarse and inhomogeneous, with severe agglomeration of TiC and TiB2 particles. The samples containing externally added 30 wt% TiC–TiB2attain the micro-hardness of 485 HV100. The microstructure evolution and fracture mode of the two kinds of NiAl–TiC–TiB2 composites are different.     

纯铜表面氩弧熔覆TiB2/Ni复合涂层组织及耐磨性能

通过氩弧熔覆技术在纯铜表面制备TiB₂增强 Ni 基复合涂层,以改善其耐磨性能. 将钛粉、硼粉和镍粉在球磨机中充分混合,采用氩弧熔覆技术将纯铜表面预置粉末熔化制备出陶瓷颗粒增强镍基熔覆层. 采用X射线衍射仪、扫描电子显微镜、透射电子显微镜分析涂层的物相及涂层中陶瓷颗粒相的组成、分布及结构,利用显微硬度仪和摩擦磨损试验机测试涂层的显微硬度和耐磨性能. 结果表明,熔覆层物相主要包括γ(Ni, Cu)和TiB₂;陶瓷颗粒增强相弥散分布于熔覆层中,其中颗粒相TiB₂以六边形存在,熔覆层内部与基体界面处均无缺陷产生;熔覆涂层具有较高的显微硬度,当(Ti+B)质量分数为10%时,涂层显微硬度高达781.3 HV,与纯铜基体对比,熔覆层显微硬度提高约11.7倍;在相同磨损条件下,随(Ti+B)质量分数的增加,熔覆涂层的摩擦系数及磨损失重先减小后增大;氩弧熔覆原位自生TiB₂陶瓷颗粒增强镍基熔覆层可显著提高纯铜表面的耐磨性能.     

Al2O3/TiB2/Al复合材料的微观结构和高温力学性能

以细雾化铝粉和TiB₂颗粒为原料,通过粉末冶金和热轧制制备微米TiB₂和纳米Al₂O₃颗粒增强铝基复合材料。室温时,由于TiB₂和Al₂O₃的综合强化作用,Al₂O₃/TiB₂/Al复合材料的屈服强度和抗拉强度分别为258.7 MPa和279.3 MPa,测试温度升至350℃时,TiB₂颗粒的增强效果显著减弱,原位纳米Al₂O₃颗粒与位错的交互作用使得复合材料的屈服强度和抗拉强度达到98.2MPa和122.5 MPa。经350℃退火1000 h后,由于纳米Al₂O₃对晶界的钉扎作用抑制晶粒长大,强度和硬度未发生显著的降低。     

Production of Al–Ti–B master alloys from Ti sponge and KBF4

It is of great interest to replace the K₂TiF₆ salt so as to reduce the volume of fluoride-bearing particulate material to be added to the aluminium melt in the popular “halide salt” process. Ti sponge was used in the present work as the source of Ti in the production of an Al–5Ti–1B grain refiner. Addition of Ti granules into molten aluminium, either premixed with or before KBF₄ salt, has produced Al–5Ti–1B alloys where the boride particles were relatively few and predominantly of the AlB₂ type. The grain refining efficiency of these alloys were far from satisfactory. TiB₂ was the dominant boride phase with sufficient number of blocky aluminide particles when Ti, in excess of the TiB₂ stoichiometry was supplied before hand and the balance was reserved for co-addition with KBF₄. Al₃Ti particles were generated soon after the Ti solubility limit was exceeded in the first step while the boride particles were subsequently produced by the reaction between molten aluminium, KBF₄ and K₂TiF₆. The Al–5Ti–1B master alloy thus produced provided an adequate grain refining performance while the amount of particulate material to be added to the aluminium melt was reduced by nearly 30%.     

激光熔覆原位合成陶瓷相增强铁基熔覆层的组织和性能

利用6 kW光纤激光器在Cr12MoV汽车模具钢表面激光熔覆含有Ti-Fe,B₄C粉末的铁基合金粉,在汽车模具钢表面直接原位合成TiC+TiB₂颗粒增强的铁基合金复合涂层.涂层与基体呈良好的冶金结合,涂层组织细小,结构致密,宏观质量较好. XRD分析结果表明,涂层组织由α-Fe,TiC,TiB₂组成. TiC,TiB₂相均匀分布于熔覆层中.由于TiC,TiB₂硬质相的形成以及激光的快速凝固冷却获得的细晶组织,使得熔覆层的显微维氏硬度有了明显提高.在距离熔覆层表面1.2 mm处显微维氏硬度高达1000 HV,有利于促进熔覆层耐磨性的提高.     

固溶处理对TiB2/6061复合材料硬度及耐磨性的影响

采用氟盐法制备了TiB₂质量分数为3%的原位合成TiB₂/6061复合材料,研究了固溶温度和固溶时间对复合材料硬度和耐磨性能的影响。结果表明:TiB₂颗粒弥散分布在6061铝合金基体中,明显细化6061铝合金基体晶粒。当固溶温度一定时,随固溶时间延长,复合材料的硬度和耐磨性可获得明显提高,但固溶时间在6~10 h时,复合材料的性能变化不显著。当固溶时间一定时,随固溶温度升高,复合材料硬度和耐磨性呈现先上升后下降的趋势。3wt%TiB₂/6061复合材料经530 ℃×10 h固溶处理后,硬度和耐磨性能最佳,相较于铸态硬度值提高了79.5％,磨损量减少了59.1%。固溶处理后复合材料的磨损表面犁沟变细变浅,材料脱落现象减少。     

Thermodynamic assessment of the Ti–B system

A consistent thermodynamic data set for the Ti–B system is obtained by means of CALPHAD technology. The sublattice model is used to describe the solid solution phases: (Ti%)₁(B, Va%)_0.5 and (Ti%)₁(B, Va%)₃ for the terminal solution (Ti) and (βTi), and Ti₁(B%, Ti)₁ and (B, Ti%)₁(B%, Ti)₂ for the compound solution TiB and TiB₂, respectively. The intermetallic compound Ti₃B₄ is treated as a stoichiometric compound. The liquid solution phase is assumed to be a substitutional solution with Redlich–Kister formula for the expression of its excess Gibbs energy. The complete T–x phase diagram for the Ti–B binary system is given. The calculation results agree well with experiments.     

原位自生TiB2/7050复合材料的高周疲劳断裂机制

TiB₂/7050铝基复合材料在航空发动机等领域具有重要的应用前景。本文研究了TiB₂颗粒质量分数为4%的原位自生7050铝基复合材料在T6热处理状态下的室温高周疲劳性能,利用扫描电子显微镜对复合材料的疲劳断裂机制进行分析。结果表明:在应力比R=?1、指定寿命为3×107周次时,TiB₂/7050铝基复合材料的疲劳强度为211.9 MPa,高于7050铝合金的疲劳强度;疲劳裂纹萌生源主要分布在近样品表面的夹杂、大尺寸的TiB₂颗粒及显微孔洞等区域;疲劳裂纹的扩展在遇到TiB₂颗粒带时,疲劳条带的宽度会明显减小,即TiB₂颗粒提高了复合材料的抗疲劳裂纹扩展能力,使得复合材料具有高的疲劳寿命。     

La2O3含量对激光熔覆TiB/Ti涂层显微结构的影响

目的 改善钛合金表面激光熔覆复合涂层的组织结构,提高钛合金的硬度,使其在相应领域得到更广泛的应用.方法 采用激光熔覆快速非平衡合成方法 制备原位反应合成L2O3-TiB增强钛基复合涂层.用L2O3、Ti和B的混合粉末在Ti-6Al-4V基体表面激光熔覆制备L2O3-TiB/Ti复合涂层,并对其进行XRD物相分析、SEM显微结构观察及显微硬度分析.结果 添加不同含量的L2O3的激光熔覆钛合金复合涂层均与基体较好的结合,涂层中均只有α-Ti和TiB两种物相.随L2O3含量的增加,激光熔覆复合涂层中的增强相TiB的形貌越均匀细小,添加不同含量的L2O3的激光熔覆复合涂层的硬度值约为基体材料的2~3倍,添加质量分数为3%的L2O3的激光熔覆复合涂层硬度最高,其显微硬度值大约为1300HV.结论 添加稀土氧化物L2O3后制备的激光熔覆钛合金复合涂层与基体结合良好,稀土元素的添加使涂层组织细化,硬度得到了明显提高.     

Microstructural characterization of NiCr1BSiC laser clad layer on titanium alloy substrate

Laser cladding of NiCrBSiC powders on Ti–6Al–4V alloy substrate was carried out, and the microstructure of the laser clad layer was characterized by TEM and SEM. Results show that the phases of TiC, TiB₂, CrB and M₂₃C₆ were formed in situ in the clad layer. The TiC phase exists in the form of dendrites with two types of interface morphology including the non-faceted and the faceted one. The TiB₂ phase nucleates on the facets of TiC dendrites, and can grow to form a special morphology of microstructure in which the TiC dendrite is encased by the TiB₂ phase. The CrB and M₂₃C₆ phases exist in the form of rod-shaped morphology, inside which stacking faults could be observed. The clad layer matrix consists of primary γ_p-Ni dendrites and lamellar eutectics of γ_e-Ni+Ni₃B. The formation mechanism of the microstructure of the clad layer was discussed.     

Sc元素对激光选区熔化TiB2/AlSi10Mg复合材料组织和性能的影响

采用稀土元素Sc对激光选区熔化TiB₂/AlSi10Mg复合材料进行变质处理,借助场发射扫描电镜、电子探针显微分析仪、显微硬度计以及电子万能试验机等,分别研究了添加Sc元素和固溶时效热处理对复合材料显微组织、密度和力学性能的影响。结果表明:与TiB₂/AlSi10Mg复合材料相比,Sc元素的加入可以进一步细化Al-Si共晶,产生细晶强化和弥散强化作用,TiB₂/AlSi10MgSc复合材料的抗拉强度和显微硬度分别提升了56.7 MPa (14.4%) 和15.3 HV0.1 (11.3%)。激光选区熔化TiB₂/AlSi10MgSc复合材料的硬度和强度随着固溶温度升高而逐渐降低,但伸长率得到明显改善。     

TiB2/Al-Si-Mg-Er复合材料的组织与性能

采用重熔稀释法制备了Al-7Si-0.5Mg-0.1Er和0.5TiB₂/Al-7Si-0.5Mg-0.1Er合金,研究了TiB₂颗粒增强Al-Si-Mg-Er复合材料的组织性能。结果表明,复合材料铸态组织主要由α-Al基体、共晶Si相和TiB₂颗粒组成。TiB₂粒子的加入使Al-7Si-0.5Mg-0.1Er合金二次枝晶间距减小了7.1 μm。抗拉强度达到217.53 MPa,较Al-7Si-0.5Mg-0.1Er合金提升了12.1 %。TiB₂/Al-Si-Mg-Er复合材料的最优T6热处理工艺为530 ℃×12 h固溶+160 ℃×7 h时效,经该工艺处理后,TiB₂/Al-Si-Mg-Er复合材料抗拉强度达到319.49 MPa,相比热处理前提高了46.9%,相比Al-7Si-0.5Mg-0.1Er合金提高了5.9%;屈服强度达到266.75 MPa,相比热处理前提高了106.4%,相比Al-7Si-0.5Mg-0.1Er合金提高了14.9%。复合材料抗拉强度的提升主要源于TiB₂颗粒加入后产生的晶粒细化、变质和热处理强化。     

Densification, microstructure and mechanical properties of TiB2-B4C based composites

The effect of boron carbide (B₄C) additions on the densification and sintering behavior of a titanium diboride (TiB₂) matrix was determined. Due to the milling process, iron and tungsten carbides (WC-Co) were included as a contaminant or a third phase in the composite. When adding from 10 to 30 wt% of B₄C to TiB₂ along with 0.5 wt% Fe sintered densities were increased from 96 to 99.9%. A small amount (0.5 wt% Fe) enhanced densification of TiB₂. However, larger quantity (5 wt% Fe) leads to volatilization of the iron when sintering at high temperature and exaggerated grain growth. Solid solutions of (Ti,W)B₂ were also detected when 3 wt% WC-Co was present. Microstructural coarsening was inhibited by incorporation of B₄C particles and mechanical properties were consequently improved.     

Microstructure of hot-pressed B4C–TiB2 thermoelectric composites

B₄C–TiB₂ thermoelectric composites were prepared via hot-pressing. The phase composition, microstructure of the samples were characterized by means of XRD, SEM and TEM. The composition of different phases, including grain boundary phase, was analyzed by means of EDS. The effects of the microstructure on the thermoelectric properties of the composites are discussed.     

Microstructural evolution and mechanical properties of in situ TiB2/Al composites under high-intensity ultrasound

Microstructural evolution and mechanical properties of in situ TiB2/Al composites fabricated with exothermic reaction process under high-intensity ultrasound produced by the magnetostrictive transducer were investigated. In this method, the microstructure and grain refining performance of the TiB2/Al composites were characterized by optical morphology(OM), scanning electron microscopy(SEM), energy-dispersive spectrometer(EDS), and X-ray diffraction(XRD) analysis.Microstructural observations show a decreasing trend in the grain size of the composites due to the ultrasound and the content of TiB2 particles in the composites. Compared with the process without ultrasound, the morphology and agglomeration of TiB2 particles are improved by high-intensity ultrasound. Meanwhile, it is proposed that the formation of TiB2 particles occurs via the transformation from Ti Al3, and at the optimal amount of the reactants, the conversion efficiency of Ti Al3 into TiB2 almost reaches up to 100 %. Finally, the effects of high-intensity ultrasound and TiB2 particles on the mechanical properties of the TiB2/Al composites were also discussed.     

Microstructure and formation mechanism of titanium matrix composites coating on Ti-6Al-4V by laser cladding

Laser cladding experiments were done on a 5-kW continuous wave CO2 laser to synthesize TiC and TiB rein- fowed titanium matrix composite coatings on Ti-6AI-4V alloy with a mixture of Ti and B4C precursor powder. The ther- modynamics of the reactions were calculated and analyzed. The microstructure and phase evolution of TiB and TiC com- posites were investigated. The results showed that the chemical reaction between Ti and B4C would release much heat, and these compounds, TiC, TiB, and small amount of TiB2, can be formed on the surface of Ti-6AI-4V alloy if the supplied en- ergy is sufficient to excite the reaction among the initial products. A good metallurgical bond between the coating and the substrate can be achieved. The microhardness of coating was irregular and the maximum value was approximately HV600.