铝液原位反应生成TiAl_3晶须的条件和机制分析

分析了液相原位反应生成 Ti B2 颗粒过程中 ,Ti Al3晶须的生成条件和生长机理。结果表明 ,预制块中 Ti与B的摩尔比显著影响 Ti Al3晶须的生成 ,Ti Al3晶须的生长机理为 VL S机制 ,由于晶须生长过程中触媒液滴中的 Ti参加反应 ,使它与一般晶须生长的 VL S机制有所不同     

双相TiAl基合金γ相中螺旋状普通位错的形成

利用自行开发的精确立体显微术研究了800℃压缩变形2％的双相TiAl基合金γ相中普通位错的空间形态。研究结果表明，同一位错往往并不处于同一晶面，其中一些位错段靠近（111）晶面，另一些则靠近（112）晶面，构成三维螺旋状曲线。普通位错形成这种螺旋状曲绠交滑移的结果，即原先在（111）密排面滑移的螺位错的部分位错段交滑移到（112）非密排面。随着处于不同晶面的位错段的进一步滑移，靠近位错段交界处的位错线方向将发生变化，具有较大刃型分量的部分可通过攀移而偏离（111）或（112）晶面。     

多弧物理气相沉积技术制备（TiAl）N超硬膜

主要介绍采用多弧物理气相沉积（ＰＶＤ）技术研制新型（ＴｉＡｌ）Ｎ超硬膜的工艺技术特点。对其膜层相结构、化学成分、显微组织等方面做了分析研究。结合工业生产实际应用进行了（ＴｉＡｌ）Ｎ与ＴｉＮ涂层刀具切削耐用度对比试验。     

高能球磨Ti/Al复合粉体的反应烧结致密行为

研究高能球磨Ti/Al复合粉反应烧结过程的致密行为 ,并进行反应烧结热力学和动力学分析。结果表明 ,与增加烧结压力、提高烧结温度或延长烧结时间的作用相同 ,高能球磨对Ti/Al粉末体反应烧结过程的致密化具有促进作用 ,且效果更加显著。球磨时间越长 ,烧结体越致密。球磨 3h的Ti/Al复合粉坯料经6 30℃× 2h预烧、12 5 0℃× 8h无压烧结后 ,获得的TiAl基合金试样的致密度高达 99 87%。球磨对Ti/Al粉末体反应烧结时致密化的促进作用 ,主要是由于Ti、Al反应组元及其晶粒尺寸的细化 ,晶格畸变能增加 ,从而显著提高了烧结驱动力和烧结动力学因子 ,缩短了反应扩散距离 ,抑制了kirkendall孔隙的形成。     

涂层对TI纤维与Ti／TiAl复合材料性能影响的研究

研究了涂层对Ｔｉ纤维及Ｔｉ纤维强化γ－ＴｉＡｌ金属间化合物基复合材料性能的影响。研究结果表明，运用物理气相沉积法（ＰＶＤ）在Ｔｉ纤维表面涂覆Ｙ２Ｏ３制得Ｔｉ／ＴｉＡｌ复合材料，不仅改善了γ－ＴｉＡｌ及其复合材料的力学性能，而且使纤维与基体间的界面反应层厚度减小，涂覆Ｙ２Ｏ３较Ａｌ２Ｏ３有较高的稳定性，这对深入研究涂层对复合材料合成及性能的影响有着重要的意义。     

Thermal expansion of TiAl + TiB2 alloys and model calculations of stresses and expansion of continuous fiber composites

Thermal expansion values for three TiAl alloys with different additions of TiB₂ can be represented using a third-order equation at temperatures between 20 and 800°C. Expansion values were obtained on both heating and cooling temperature cycles. The total expansion at 800°C is between 0.917 and 0.931% for three different samples. The expansivity increases from about 10×10^–6°C^–1 at 80°C to 14×10^–6°C^–1 at 750°C. A five-coaxial cylinder elastic model for multizone-coated continuous fiber composites is developed for predicting stresses and thermal expansion of composites. Either isotropic or transversely isotropic material properties can be assigned to the various cylinder zones.Paper presented at the Tenth International Thermal Expansion Symposium, June 6–7, 1989, Boulder, Colorado, U.S.A.     

Lamellar boundary alignment of DS-processed TiAl−W alloys by a solidification procedure

In this study, a β solidification procedure was used to align the lamellae in a Ti-47Al-2W (at.%) alloy parallel to the growth direction. The Bridgman technique and the floating zone process were used for directional solidification. The mechanical properties of the directionally solidified alloy were evaluated in tension at room temperature and at 800°C. At a growth rate of 30 mm/h (with the floating zone approach), the lamellae were well aligned parallel to the growth direction. The aligned lamellae yielded excellent room temperature tensile ductility. The tensile yield strength at 800°C was similar to that at room temperature. The orientation of the γ lamellar laths in the directionally solidified ingots, which were manufactured by means of a floating zone process, was identified with the aid of electron backscattered diffraction analysis. On the basis of this analysis, the preferred growth direction of the bcc-β dendrites that formed at high temperatures close to the melting point was inferred to be [001]_β at a growth rate of 30 mm/h and [111]_β at a growth rate of 90 mm/h.     

TiAl-W-Si合金中的偏析与析出相的分析电子显微术研究

用高空间分辨分析电子显微术研究了TiAl-W-Si合金中B2相的析出行为和元素W的分布.结果表明,α2/γ相界面台阶由于W的富集而成为B2析出相的择尤形核位置.B2相中,高达三分之一的Al原子被W原子置换,而在γ相中只固溶了很有限的W.另外,W也偏析在α2/γ和B2/γ相界面上.这些结果合理地解释了W对提高TiAl合金蠕变性能的显著作用.     

Microstructure degradation in high temperature fatigue of TiAl alloy

Low cycle fatigue properties of lamellar TiAl with 8 at.% Nb were studied at four temperatures: room temperature, 700, 750 and 800 °C. Up to 750 °C, stable cyclic behaviour is observed while cyclic softening is characteristic for 800 °C. The strength of the alloy is still high even at 800 °C. The TEM observation did not reveal any substantial changes in the microstructure due to the cycling at RT. At 750 °C, the lamellar structure was in some places destroyed by cyclic plastic straining and pure γ-phase islands with high density of dislocation debris were formed. At 800 °C, the domains without lamellar structure cover about 10% of volume and are almost dislocation free. The destruction of lamellar microstructure and possible annealing of dislocation debris is the reason for marked cyclic softening at 800 °C.     

Direct Friction Welding of TiAl Alloy to 42CrMo Steel Rods

The effect of post-weld heat treatment (PWHT) on the mechanical properties and microstructure of direct friction-welded joint between TiAl alloy and 42CrMo steel rods was investigated in this paper. It was found that solid joint between TiAl alloy and 42CrMo steel could be obtained without adding interlayer. After PWHT at 580°C for 2 h, the tensile strength of the joint reached 405 MPa, and fracture happened through the TiAl alloy substrate with quasi-cleavage features. The tempered sorbite formed near the interface, improving the joint strength significantly. It was found that TiFe₂, TiAl, and small amount of TiC brittle phases formed at the interface, and the interfacial layer was as thin as 2–5 µm. The precipitated phases were 1 µm in average size, and distributed discontinuously at the interface.