利用透射电子显微镜，采用双倾双束技术和ｇ·ｂ不可见判据，分析了Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ（ａｔ．－％）合金中α_２相（Ｄ０_（１９）结构）在２５—７００℃拉伸形变时的位错类型和滑移系．结果表明：室温拉伸形变主要源于ａ型位错在棱柱面或基面滑移，如〈１１０〉｛１００｝，〈１１０〉｛０００１｝；和少量＋／２型位错对在棱锥面滑移，如〈１１６〉｛２０１｝；＋／２，型位错密度随形变温度提高而减少，４００℃拉伸形变时出现大量孪晶；７００℃形变时没有＋／２型位错对出现，开动的是主要型位错在棱柱面、基面滑移和型位错对在棱锥面滑移，如〈１１０〉｛２１０｝．
The tensile deformation mechanism of α_2-phase (DO_(19)) in a Ti-25Al-10Nb-3V-1Mo alloy at 25—700℃ was studied. In accordance with . =0 invisibility criterion, dislocation types and slip systems were analysed in a TEM equipped with a side entry goniometer stage capable of a ± 45°tilt on X- and Y-axis operating under two-beam condition. Experimental results show that the majority of slip systems activated at 25—700℃ are type dislocation on prismatic and basal planes. A few of / 2 type dislocation pairs on pyramidal plane are found at 25℃, so a large amount of twinning found at 400℃.The density of/2 type dislocation pairs decrease with the increase of temperature. No/2 type dislocation pair is found at 700℃, but some type dislocation pairs are activated at 700℃. Correspondent:SUN Fusheng, senior engineer,（Institute of Aeronautical Materials, Beijing 100095）
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