新型高强韧Ti-Al-Fe-B系钛合金组织和性能研究

Study on Microstructure Evolution and Mechanical Properties of New Ti-Al-Fe-B Titanium Alloy with High Strength and Ductility

摘要:

本文研究了不同含量Al元素(1~3wt.%)的添加及热处理工艺对合金Ti-xAl-3.5Fe-0.1B组织和力学性能的影响。研究结果表明：Ti-xAl-3.5Fe-0.1B为α+β 两相钛合金，随着Al元素含量由1%增加到3%，合金屈服强度由590 MPa提高到900 MPa，抗拉强度由808 MPa提高到1074 MPa，固溶强化明显，同时，延伸率达到15.4%。组织观察发现：随着Al元素含量的增加，片层状初生α相片层厚度减小，合金组织细化明显。另一方面，对Ti-3Al-3.5Fe-0.1B合金进行不同的热处理发现：双重退火后，合金的屈服强度进一步提高到1000 MPa，抗拉强度提高到1144 MPa，同时，塑性也提高到17.5%，合金具有优异的强韧匹配性。这主要是因为合金双重退火过程中，组织中生成的亚稳β相分解生成次生α相，次生α相尺寸小，位错在次生α相边界受阻。同时，次生α相在β基体上弥散分布，形成弥散强化，导致合金强度进一步提高。另一方面，组织中等轴α相的存在，对于塑性的提高起到了积极的作用。

Abstract:

In the present study, Effect of Al element addition (1~3wt.%) and heat treatment on microstructure evolution and mechanical property of one new alloy Ti-xAl-3.5Fe-0.1B was studied. Results indicated that Ti-xAl-3.5Fe-0.1B is α+β two-phase titanium alloy. Yield strength of the alloy increased from 590MPa to 900MPa and tensile strength increased from 808MPa to 1074 MPa with the variation of Al element from 1% to 3% due to solid solution strengthening effect, at the same time, the elongation to failure reduced to 15.4%. Microstructure observation revealed that the thickness of the lamellar primary α phase reduced and the grain size remarkably refined as the increasing Al element content. Meanwhile, It was found that yield strength continuously increased to 1000 MPa, tensile strength increased to 1144 MPa and the elongation to failure increased to 17.5% separately after double annealing, which indicated unique mechanical property. The metastable β phase formed in the microstructure decomposed to secondary α phase with fine grain size during the double annealing in the alloy, which blocked the movement of dislocation and induced enhancement of strength, at the same time, the dispersion of secondary α phase on β substrate was also beneficial to the strength. On the other hand, the present of equiaxed α phase was considered favorable to the improvement of elongation to failure.