Fe对Ti-6Al-4VELI合金力学性能的影响

The Influence of Fe on the Mechanical Properties of Ti-6Al-4V ELI Alloy

研究了Fe含量(0.03%-0.24%,质量分数)对Ti-6Al-4V ELI(TC4 ELI)合金力学性能的影响。利用EBSD对合金显微组织进行了表征,对3种不同Fe含量的TC4 ELI的拉伸性能、断裂韧性和疲劳裂纹扩展速率(da/d N)、蠕变性能进行了对比分析。结果表明:随着Fe含量增加,在保持断裂韧性不变的同时,TC4 ELI合金的抗拉强度获得提高;3种Fe含量的TC4 ELI合金在室温和200℃时的疲劳裂纹扩展速率相当,而400℃条件下提高Fe含量将增大da/d N;低于350℃时,提高Fe含量能够增强合金的抗蠕变能力,而高于350℃时,Fe的作用相反。分析可知:微量Fe在β相内富集,具有固溶强化作用,从而提高了合金的抗拉强度;高于350℃时,Fe具有加速扩散作用,加速了基体内原子和界面的运动,导致裂纹尖端塑性区内位错运动阻力降低,从而提高了da/d N,并且Fe加快了位错攀移的过程,提高蠕变速率,而低于350℃条件下,扩散运动减弱,Fe主要起到强化作用。

The effect of different Fe contents（0.03%, 0.17%, 0.24%） on the mechanical properties of Ti- 6Al- 4V ELI（TC4 ELI） alloy was studied. The microstructures were characterize by using EBSD, and the tensile properties, fracture toughness and fatigue crack growth rates（da/d N）, creep properties of TC4 ELI with three Fe contents were compared and analyzed. The results showed that with the increase of Fe contents, Fe has no apparent influence on fracture toughness, however, tensile strength of the alloy was improved. The da/d N of the three TC4 ELI alloys were found to be almost identical at room temperature and 200℃, however da/d N was found to be marginally faster as Fe contents increased at 400℃. Within the range of 250~350℃, Fe improved creep resistance, while from 350℃ to 400℃, Fe had opposite effect. Fe atom was mainly enriched in β phase. And the tensile strength was improved with the increase of Fe contents due to the solid solution strengthening effect. Because of the high diffusing rates of Fe atom under the condition of 400℃, the movement of matrix atoms and interfaces were accelerated. So that,the resistance to dislocation motion in crack tip plastic zone was reduced, which led to higher da/d N. Under the condition of 350-400℃, Fe could improve the creep rate by speeding up the process of dislocation climbing, but the reinforcement is more important below 350℃ because of the weak diffusion.