Nano Titanium Monoxide Crystals and Unusual Superconductivity at 11 K

Nano TiO₂ is investigated intensely due to extraordinary photoelectric performances in photocatalysis, new‐type solar cells, etc., but only very few synthesis and physical properties have been reported on nanostructured TiO or other low valent titanium‐containing oxides. Here, a core–shell nanoparticle made of TiO core covered with a ≈5 nm shell of amorphous TiO_1+x is newly constructed via a controllable reduction method to synthesize nano TiO core and subsequent soft oxidation to form the shell (TiO_1+x). The physical properties measurements of electrical transport and magnetism indicate these TiO@TiO_1+x nanocrystals are a type‐?? superconductor of a recorded T_c^onset = 11 K in the binary Ti–O system. This unusual superconductivity could be attributed to the interfacial effect due to the nearly linear gradient of O/Ti ratio across the outer amorphous layer. This novel synthetic method and enhanced superconductivity could open up possibilities in interface superconductivity of nanostructured composites with well‐controlled interfaces.     

T2钛合金高温腐蚀行为研究

采用高温熔盐灼烧法研究T2钛合金高温腐蚀动力学及腐蚀行为.分别在500,600,700,800℃的Na2SO4或Na2SO4(80%) NaCl(20%)环境中发现T2钛合金腐蚀增重符合直线规律,直线通式为y=KLt.随着温度的增加,直线的速率常数KL增大.混合盐Na2SO4(80%) NaCl(20%)比纯Na2SO4的加速腐蚀作用更加明显.在Na2SO4或Na2SO4(80%) NaCl(20%)中,T2钛合金随温度升高,氧化膜的完整性降低.合金中Al,Zr等元素在腐蚀中向合金表面扩散,而盐中的S,Cl等元素则向合金内部扩散.     

高温钛合金焊接研究现状及展望

综述了国内外高温钛合金焊接研究的发展现状。总结了高温钛合金的焊接特点及其对高温钛合金焊接接头热强性与热稳定性、蠕变疲劳抗性的一致性、均匀性和稳定性的要求,介绍了闪光对焊、线性摩擦焊、电子束焊接和激光焊接技术的研究现状,并对高温钛合金焊接未来研究方向进行了展望。     

Ti-Al-Zr-Mo-Nb-Sn-Si系铸造钛合金高温蠕变性能及显微组织研究

针对Ti-Al-Zr-Mo-Nb-Sn-Si铸造高温钛合金,研究了其在600℃、750℃下的蠕变性能与组织变化。结果显示,该铸造钛合金在750℃/180 MPa/0.5 h和600℃/400 MPa/0.5 h条件下的蠕变残余伸长率分别<3%和<0.4%,持久断裂时间分别为>2 h和14 h,具有良好的蠕变性能;高温蠕变断口存在细小颗粒;高温蠕变后塑性变形区的组织变化较小,呈魏氏组织,而集中变形区存在部分晶界消失、α片层宽化现象;高温蠕变后位错明显增多,与析出相相互纠缠。     

钛合金焊接冶金研究进展

概括介绍了钛合金焊接的主要特点 ,综述了钛合金焊接冶金方面的研究进展 ,并阐述了该领域的研究前景。     

表面纳米化对高温Ti合金与TiAl合金的扩散连接工艺及力学性能影响

目的研究表面纳米化Ti合金与Ti Al合金异质扩散连接的界面反应、力学性能和工艺条件。方法利用高能喷丸技术对钛合金的表面进行纳米化处理,然后在高温压力真空炉内进行扩散连接实验。结果 Ti合金/Ti Al扩散连接的结合强度与中间层厚度密切相关,当中间层厚度为1.7~2.0μm时,剪切强度最大。结论表面纳米化可以促进原子扩散、增加接头厚度、缩短扩散连接所需的时间。对于扩散界面存在缝隙接头,在无压热处理条下表面纳米化样品可以快速提高焊合率,改善连接质量。     

Decompression‐Driven Superconductivity Enhancement in In2Se3

An unexpected superconductivity enhancement is reported in decompressed In₂Se₃. The onset of superconductivity in In₂Se₃ occurs at 41.3 GPa with a critical temperature (T_c) of 3.7 K, peaking at 47.1 GPa. The striking observation shows that this layered chalcogenide remains superconducting in decompression down to 10.7 GPa. More surprisingly, the highest T_c that occurs at lower decompression pressures is 8.2 K, a twofold increase in the same crystal structure as in compression. It is found that the evolution of T_c is driven by the pressure‐induced R‐3m to I‐43d structural transition and significant softening of phonons and gentle variation of carrier concentration combined in the pressure quench. The novel decompression‐induced superconductivity enhancement implies that it is possible to maintain pressure‐induced superconductivity at lower or even ambient pressures with better superconducting performance.     

Charge-Density-Wave Pseudogap and Two-Dimensional Superconductivity Within Strong-Coupling Description

We have considered the role of charge-density-pseudogap for phonon-mediated super-conductivity on two-dimensional lattice. The propagators that enter generalized Eliashberg equations have been renormalized to account for quasi-particle energies related to the formation of the pseudogap, which has been assumed to be of d-wave symmetry. We have evaluated the superconducting transition temperature T_c as a function of doping. It occurs that T_c for d-wave symmetry well reflects experimental behavior. Our results for the isotope shift exponent show that at low doping, the presence of the pseudogap may contribute to > 1/2 as well as to > 1/2 values.     

高强TA18钛管数控弯曲织构演变数值模拟

目的获得高强TA18钛管数控弯曲过程的织构演变规律。方法基于高强TA18钛管数控弯曲三维弹塑性显式有限元模型以及耦合粘塑性自洽晶体塑性模型(VPSC),获得钛管数控弯曲过程中的织构演变规律,通过单向拉伸、压缩和数控弯曲实验与EBSD分析验证了织构演变预测的可靠性。结果高强TA18钛管数控弯曲过程中,弯曲角度为0°~90°时,弯曲后管材内外侧均形成径向织构与轴向织构。结论高强TA18钛管的初始织构为近径向织构,在数控弯曲过程中,随弯曲角度增大,管材内侧轴向织构逐渐增多,径向织构先减小后增大;管材外侧的周向织构与轴向织构都逐渐增加;实验对比分析表明,预测的织构变化趋势和实验结果基本一致。     

高强 TA18 钛管连续整体多弯成形精度控制

目的研究获得基于多指标的高强TA18钛管整体多弯管件成形精度控制的方法。方法在获得高强TA18钛管数控弯曲非线性回弹和伸长规律的基础上,研究回弹角、回弹半径的补偿方法和伸长控制方法,其次将获得的成形精度控制方法进行多弯模拟应用验证。结果对于回弹角和回弹半径,采用先补偿回弹半径再补偿回弹角的两水平顺序控制方法;对于弯曲伸长,采用预先减少管材下料尺寸和改变弯头位置来控制回弹后直线段长度的控制方法。结论应用上述控制方法,将多弯模拟结果与预成形管件几何尺寸进行对比,获得成形角度、半径和直线段长度的最大相对误差分别为1.00%,5.51%和5.04%。上述误差满足多弯管件装配精度要求,证明所提出的成形精度控制方法是可靠的。     

Influences of Friction Stir Welding and Post‐Weld Heat Treatment on Al–Cu–Li Alloy

In this paper, the influences of friction stir welding (FSW) and post‐weld heat treatment (PWHT) on the microstructures and tensile properties of Al–Cu–Li alloy are investigated. After FSW, strengthen loss occurred in the welding area. Remarkable softening occurs in the thermo‐mechanically affected zone (TMAZ) resulting from dissolution of Al₃Li (δ′) phases. Recrystallization and precipitation of ultra‐fine δ′ phases take place in the nugget zone (NZ) that lightens the softening degree of this zone. A noteworthy enhancement in the hardness and tensile strength of the joint is achieved after T8 re­aging treatment (3% ? pre‐deformation, 30 h at 152 °C). However, re‐solution treatment coupled with re‐aging treatment leads to ductility deterioration in the joint because coplanar slip of coarse Al₃Li phases induces severe stress concentration during plastic deformation.

     

CMT焊接技术在钛合金方面的应用研究

CMT(Cold Metal Transfer)冷弧焊是一种新型的熔化极气体保护电弧焊方法。该方法通过采用数字化电源和过程的精密控制技术,使得在焊接过程中可大幅度降低焊接热输入量,从而减小焊接残余应力和焊接变形。本文通过对不同厚度钛合金的CMT焊接研究,在坡口制备、焊接参数等方面确定了技术要求,成功应用于不同规格厚度的钛合金的规模化生产。     

TA15钛合金的高周疲劳性能和断裂特征

研究了双态组织的TA15钛合金的高周疲劳性能和疲劳断裂特征,结果表明,β转变组织中次生α相的数量和形态对疲劳性能有显著影响,次生相α相的球化显著降低了合金抗裂纹扩展的能力,而大量的片状次生α相则通过造成疲劳裂纹的分枝有效地降低了疲劳裂纹的扩展速度,提高了疲劳极限.     

Titanium Incorporation into Zr‐Porphyrinic Metal–Organic Frameworks with Enhanced Antibacterial Activity against Multidrug‐Resistant Pathogens

This study uses metal–organic frameworks (MOFs) alone without any added antibacterial ingredients as the nonantibiotic agent for photodynamic therapy (PDT) of chronic wounds infected by multidrug‐resistant (MDR) bacteria. Nanoparticles (NPs) of MOFs (PCN‐224) are incorporated with titanium through a facile cation exchange strategy. The obtained bimetallic PCN‐224(Zr/Ti) shows greatly enhanced photocatalytic performance for the generation of reactive oxygen species under visible light, which is responsible for the effective antibacterial activities. The PCN‐224(Zr/Ti) NPs are loaded onto lactic‐co‐glycolic acid nanofibers to prepare a wound dressing, which shows high biocompatibility and minimal cytotoxicity. The wound dressing is efficient for PDT‐based in vivo healing of the chronic wound infected by MDR bacteria. Most importantly, this work does not involve any additional antibacterial agents, which is facile, low cost, and in particular, greatly explores the potential of MOFs as a powerful nonantibiotic agent in PDT.     

Experimental Study on the Effect of Cooling Rate on the Secondary Phase in As‐Cast Mg–Gd–Y–Zr Alloy

The effect of cooling rate on the composition, morphology, size, and volume fraction of the secondary phase in as‐cast Mg–Gd–Y–Zr alloy is investigated. In the study, a casting containing five steps with thickness of 10–50 mm is produced, in which cooling rate ranging from 2.6 to 11.0 K s^?1 is created. The secondary phase is characterized using optical microscope (OM), scanning electron microscope (SEM), and electron probe micro‐analyzer (EPMA). The volume fraction of the secondary phase is determined using OM and quantitative metallographic analysis, and Vickers hardness test is conducted to verify the analysis results. The effect of the cooling rate on the volume fraction of the secondary phase is discussed in detail. The result shows that with the increase of the cooling rate, the size of the secondary phase decreases. The effect of the cooling rate on the volume fraction of the secondary phase is complicated somewhat. A comprehensive analysis on the experimental data shows that a critical cooling rate may exist, over which the volume fraction of the secondary phase decreases with the increase of the cooling rate, however under which the volume fraction increases with the increase of the cooling rate.

     

BT22钛合金及其大型锻件的研究进展

综述了国内外BT22合金及其改型合金的应用现状,归纳介绍了BT22合金的锻造加工及热处理工艺.结果表明,BT22合金在两相区低于β_转15～50℃的温度范围内多火次锻造,每火次变形量不低于60%.通过严格控制变形速率和终锻温度可制备出组织均匀、晶粒细小的锻件,经两阶段整体热处理后可获得强度、塑性和韧性的最佳匹配.针对我国的研究现状指出了BT22合金大型锻件制备方面亟待解决的问题和未来研究发展的方向.