原位自生Ti2AlC增强TiAl合金组织与力学性能影响研究

Microstructure and mechanical properties of TiAl alloy reinforced by in-situ Ti2AlC

摘要:

采用真空电弧熔炼炉制备了原位自生Ti2AlC增强Ti-48Al-2Cr-2Nb合金,研究了CNTs含量对TiAl基合金的组织演变和力学性能的影响。结果表明,随着CNTs的增加,合金的凝固路径向高Al方向移动,γ相含量增多,与此同时片层组织逐渐细化,Ti2AlC的长径比逐渐减小。在固溶强化、细晶强化以及Ti2AlC析出相强化的作用下,合金的力学性能得到显著提高。随着CNTs含量的增加,合金的维氏硬度由358.4±19.2 HV提高到了428.5±23.1 HV。合金的室温压缩强度和高温压缩强度均随着CNTs的增加先增加后减小。当CNTs添加量为3.0 at.%时,其室温压缩强度和最大应变分别达到1890.61 MPa和29.09%,分别提升54.95%和28.31%。在800 ℃压缩中,合金的硬化和软化效果受CNTs含量影响,3.0 at.% CNTs的合金表现出最高的压缩强度,相比于未添加CNTs时提升约31.42%,而4.5 at.% CNTs的合金在不影响压缩强度的情况下表现出较好的软化效果。

Abstract:

Ti-48Al-2Cr-2Nb alloy reinforced by in-situ Ti2AlC was prepared by vacuum arc melting. The effect of CNTs content on the microstructure evolution and mechanical properties of TiAl alloy was investigated. The results show that with the increase of CNTs, the solidification path of the alloy moves to the direction of high Al and the volume fraction of γ phase increases. Meanwhile, the lamellar structure is gradually refined, and the length-diameter ratio of Ti2AlC gradually decreases. The mechanical properties of the alloy incresase significantly under the action of solid solution strengthening, grain refinement strengthening and Ti₂AlC precipitated phase strengthening. With the increase of CNTs content, the Vickers hardness of the alloy increases from 358.4±19.2 HV to 428.5±23.1 HV. The compressive strength at room temperature and high temperature of the alloy first increases and then decreases with the increase of CNTs. When the addition of CNTs is 3.0 at.%, the compressive strength and maximum strain at room temperature reach 1890.61 MPa and 29.09%, respectively, which increase by 54.95% and 28.31%, respectively. At 800 ℃, the hardening and softening effects of the alloy are affected by the CNTs content. The alloy with 3.0 at. % CNTs shows the highest compressive strength, increasing by about 31.42% compared with without CNTs addition, and the alloy with 4.5 at. % CNTs shows better softening effect without sacrificing the compressive strength.