Ti-Al-Zr-Sn-Mo-W-Si系热强钛合金析出相及其对强韧性的影响

Precipitation Phases and Their Effects on Strength and Toughness of Ti-Al-Zr-Sn-Mo-W-Si Series Thermal-Strength Titanium Alloy

摘要:

对比分析Ti-Al-Zr-Sn-Mo-W-Si系热强钛合金TC25和TC25G合金抗拉强度和冲击韧性差异，通过SEM断口形貌观察和TEM微观变形机制分析，阐明了2种合金冲击韧性差异的根本原因和合金强化机制。结果表明，TC25G合金冲击断口中析出相为ZrSi或TiZrSi化合物，起到了第二相强化作用，有利于提升合金强度；因析出物有利于冲击裂纹的扩展，因而降低了合金的冲击韧性。TC25合金冲击断口显微组织中裂纹一般沿初生α相相界延伸，使得TC25合金裂纹延伸路径更长，而TC25G裂纹穿过初生α相，因而TC25合金具有更高的冲击韧性。TEM观察结果表明，TC25G合金中位错滑移痕迹和位错塞积数量明显多于TC25合金，在TC25G合金中析出相附近存在较多的位错塞积，进而产生明显的强化作用，使得合金具有较高的强度。

Abstract:

Comparative analysis of the differences in tensile strength and impact toughness between the TC25 alloy and TC25G alloy of Ti-Al-Zr-Sn-Mo-W-Si series titanium alloys was carried out, and the root causes of the differences in impact toughness between the two alloys and the alloy strengthening mechanism were elucidated through the observation of the SEM fracture morphology and the analysis of the TEM microscopic deformation mechanism. The results show that the precipitated phase in the impact fracture of TC25G alloy is ZrSi or TiZrSi compounds, which plays the role of second-phase reinforcement and is conducive to the enhancement of the alloy strength, and the precipitates are conducive to the extension of impact cracks, thus reducing the impact toughness of the alloy. In the microstructure of the impact fracture of TC25 alloy, the cracks generally extend along the primary α phase boundary, so the TC25 alloy crack extension path longer. While TC25G alloy cracks cross through the primary α phase. Thus, the TC25 alloy has higher impact toughness. TEM observations show that the number of dislocation slip traces and dislocation plugging in TC25G alloy is significantly higher than that in TC25 alloy. The presence of a large number of plugged dislocations in the vicinity of the precipitates in TC25G alloy results in significant strengthening, leading to a higher strength of the alloy.