Hot Deformation Behaviors in Ti-6Al-4V/(TiB + TiC) Composites

Thermal compression testing was investigated using the Gleeble 3800 thermal simulator,and thermal deformation behavior of particle-reinforced titanium matrix composites (TMCs) was studied under deformation temperatures of 750-900 ℃,strain rates of 0.001-1 s-1,and experimental deformation of 60％.According to obtained flow stress curves,the hot deformation characteristics were analyzed.Based on the Arrhenius hyperbolic sinusoidal model,the constitutive equation at high tempera-ture was established.Based on the theory of dynamic material models,a hot processing map of TMCs at high temperature was established,and the peak region of power dissipation rate and the instability region in the hot processing map were both determined.At the same time,the corresponding microstructures in the peak power dissipation rate and rheological instability regions were observed.The results showed that flow stress decreased with increasing deformation temperature and increased with increasing strain rate.The thermal deformation activation energy of titanium matrix composites was 301.8 kJ/mol.The Ti-6Al-4V/(TiB + TiC) composites possessed only one instability zone under high-temperature compression at a strain of 0.5,with corresponding temperatures at 750-840 ℃ and strain rates at 0.1-1 s-1.The optimal thermal deformation parameters included corresponding temperatures of 830-880 ℃ and strain rates of 0.001-0.05 s-1.The microstructures corresponding to optimal hot working parameters in processing maps were more homogeneous than the microstructures in the instability zone,including the distribution uniformity of reinforcement and the degree of dynamic recrystallization,and no instability phenomena including abnormal grain growth,microcracks or intensive fracture of reinforcements were found,indicating that the hot processing map had a positive guiding effect on the option of desirable material thermal-working parameters.     

等离子喷涂铝电解可湿润TiB2阴极涂层研究进展

铝电解工业越来越多的采用石墨阴极,石墨阴极具有良好的导电性能,但石墨不被铝液湿润且和铝液形成Al4 C3,导致铝电解槽运行寿命短.可湿润TiB2涂层阴极因节能和延长槽寿命能够给铝电解工业带来显著效益.等离子喷涂是一种高效、灵活的沉积涂层的方法 ,能够在形状复杂或大表面积的基体上沉积金属间化合物、陶瓷或复合材料,涂层厚度可从数微米到数毫米.等离子喷涂制备可湿润性TiB2涂层阴极是可行有效的方法 ,本文评述了等离子喷涂制备可湿润TiB2阴极涂层的研究进展,简述了等离子喷涂工艺受到的影响因素(包括粉末性质、基体表面形貌和焰流性质)和涂层与基体材料结合的机制(包括机械结合、冶金结合和物理结合),分析和讨论了TiB2粉末制备、基体预处理、等离子喷涂工艺参数、涂层显微结构和性能等.最后,指出了等离子喷涂制备可湿润性TiB2涂层阴极工艺将来研究需要解决的几个关键问题.     

固溶处理对TiB2/7050Al复合材料组织与性能的影响

研究了固溶处理对TiB₂/7050Al复合材料组织与性能的影响规律。结果表明,TiB₂/7050Al复合材料内的可溶性第二相主要为MgZn₂(η相)、AlZnMgCu(T相)和Al₂CuMg(S相)。η相在470℃已完全溶解,T相在476℃开始溶解,S相在491℃下可完全溶解。随固溶温度的升高,复合材料的强度整体呈上升趋势,但伸长率先增加后降低。在480℃固溶时,复合材料同时具备高强度和高塑性,其屈服强度、抗拉强度和伸长率分别为658 MPa、719 MPa和11.3%;继续升高固溶温度至490℃,虽然可使铝基体内残余S相完全溶解,但也使基体再结晶晶粒异常长大,降低了复合材料的塑性。     

真空阴极电弧沉积TiB2薄膜的组织结构及其摩擦学性能的研究

用TiB2作阴极靶，采用优化的真空阴极电弧沉积工艺制备的TiB2薄膜是由TiB2，Ti2B5,TiB和Ti组成的多相结构。薄膜的摩擦磨损试验表明：TiB2薄膜的摩擦系数为0.139，膜层寿命超过60min，是TiN和（Ti,Al)N膜层的2倍。     

TiB2涂层用于三层液铝电解精炼中的性能研究

本文研究三层液铝电解精炼温度下，静、动态电解质和精铝液体对以石墨为基底的ＴｉＢ２－石墨胶复合涂层的侵蚀、浸润性能，以及这种涂层在精铝液体中的溶解性能。初步的实验结果表明，在三层液铝电解精炼条件下，这种涂层的化学稳定性良好，能够抵抗精炼电解质和精铝液体的侵蚀；相对精炼电解质而言，铝液对涂层的浸润能力更强，通电电解时，在涂层阴极底面生成的精铝能形成铝液镜面；而且使用这种涂层作三层液铝电解精炼槽的固体阴极，不会对铝液造成严重污染；精铝质量可达９９．９８ｗｔ％以上。因此使用ＴｉＢ２复合涂层作固体阴极，将能为降低三层液铝电解精炼槽的极距，大幅度节省电能创造条件。     

TiB2粉末化学镀银工艺研究

采用化学镀银法制备Ag/TiB2复合粉末,系统研究NaOH,HCHO,NH.3H2O的加入量及反应时间等参数对包覆粉末质量的影响及TiB2表面改性对AgTiB2材料性能的影响。结果表明:NaOH和HCHO含量的增加可促进Ag的还原反应;pH值的大小对Ag的还原有显著的影响,pH值大可加快反应过程,使Ag的还原更加彻底;NH3.H2O在化学镀银过程中起稳定作用,随着NH3.H2O的增加,使反应液更为稳定,Ag不易发生自分解,但也导致镀银溶液中主盐的Ag不容易被还原,不能获得Ag均匀包覆的TiB2复合粉末;反应时间的延长对于反应后粉末中Ag含量的增加影响并不十分明显。采用化学镀的粉末所制备的Ag/TiB2复合材料的致密度、硬度和电导率分别提高了4.59%,12.20%和7.91%。     

Strategy to design high performance TiB2-based materials: Strengthen grain boundaries by solid solute segregation

TiB₂ exhibits a unique combination of excellent properties that make it promising candidate for applications in extreme environments, where retention of strength at high temperatures is essential. Tailoring grain boundary properties by segregation is believed a prominent way to design high-temperature performance of ceramics. In this work, segregation tendencies of solute elements, including Sc, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, in TiB₂ grain boundaries and the strengthening/weakening effects induced by segregations are investigated by first-principles calculations. The results reveal that small atoms tend to segregate to grain boundary sites with local compression strains, while large atoms prefer grain boundary sites with local expansion strains. Deteriorated grain boundary strength is usually caused by additional expansion strain induced by segregation, while improved grain boundary strength results from either enhanced local bonding induced by segregation of small atoms or increased fracture strain due to segregation of large atoms. Cr and V, especially Cr, exhibit strong segregation tendency and improvement on grain boundary strength, which provides useful guidelines for the design of high performance TiB₂-based materials.     

Microstructure and mechanical property of (TiB2-SiC) agglomerate-toughened B4C-TiB2-SiC composites

B₄C-TiB₂-SiC composites toughened by (TiB₂-SiC) agglomerates were prepared via reactive hot pressing with B₄C and TiSi₂ as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB₂-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the in situ formed TiB₂ and SiC were interlocked to form special (TiB₂-SiC) agglomerates in the matrix. The good comprehensive performances of 510 MPa flexural strength, 5.84 MPa·m^1/2 fracture toughness, and 31.93 GPa hardness were obtained in the composites fabricated with 30 wt% TiSi₂. The in situ introduced fine TiB₂ and SiC grains refined the grains of B₄C due to the pinning effect, which enhanced the strength. The special (TiB₂-SiC) agglomerates and the existing toughening phenomena such as crack deflection, branching, and microcrack regions induced by the mismatch of thermal expansion coefficients, had cumulative effects on improving the fracture toughness.     

TiB2含量对17-4PH钢熔覆层组织及性能的影响

目的 选择合适的TiB2添加量以提高17-4PH钢熔覆层的综合性能.方法 采用金属粉末注射成形技术制备17-4PH基体,在基体上通过激光熔覆含有不同质量分数TiB2(0.5％,1％,2％,3％,4％)的混合粉末制备样品,分析其物相及组织,测试材料显微硬度,并进行摩擦磨损与电化学腐蚀实验.通过对样品进行耐磨性与耐腐蚀性的...     

Ti-6Al-4V合金表面激光熔覆NiCrBSi＋5%BN涂层组织和性能

Ti-6Al-4V合金具有比强度高、耐蚀性能好等优点,在航天、航空、石油和化工等新科技工业部门广泛使用。在表面激光熔覆金属-陶瓷复合涂层是改善钛合金性能的重要方式,利用XRD、SEM和EDS等分析手段对NiCrBSi＋5%（质量分数）BN熔覆层的微观组织进行分析。利用HV-1000型显微维氏硬度计测试激光熔覆试样的硬度。