Ti6242合金组织演化的精细分析

Fine Analysis of Microstructure Evolution of Ti6242 Alloy

摘要:

以等轴组织Ti6242合金为研究对象，采用光学显微镜与扫描电镜两种组织观察手段，结合图像处理软件的自动处理与统计学方法，分析了不同热处理制度下合金组织的精细特征与演变规律。建立了采用体积分数Vα、尺寸Dα、分布密度ρα和聚集程度Eα四个参量来精确定量描述等轴初生α相特征及演化的方式，发现Vα、Dα、ρα和Eα均随固溶温度的升高而减少，Vα和ρα分别满足线性和抛物线规律；Vα的减少速度随温度升高而增加，随时间的延长而降低。随Vα减少，β相中Al元素含量增加，Sn、Zr和Mo三元素含量均降低；四种合金元素在α与β两相中的含量差异变小。850℃与800℃下，β相的[Mo]eq分别落入α+β型和亚稳β型钛合金对应的[Mo]eq区间，水淬后β相分别发生马氏体转变和保留亚稳态。

Abstract:

Microstructure characterization and evolution analysis of Ti6242 alloy with equiaxed microstructure was studied by optical and scanning electronic microscopes, combining with image processing software. The origin alloy was processed under different heat treatments. Four parameters, including volume fraction Vα, size Dα, distribution density ρα and degree of aggregation Eα, were used to accurately describe the characteristics and evolution process of the equiaxed primary α phase. It was found that Vα, Dα, ρα and Eα all decrease with the solution temperature T increasing, and the relationships of Vα vs. T and ρα vs. T satisfy the linear and parabolic law, respectively. The declining rate of Vα increases with the T arising and decreases with time prolonging. With the Vα dropping, the content of element Al in β phase increases, while the content of Sn, Zr, and Mo decreases; the difference of the content of the four alloying element in β and α phase becomes smaller. At 850℃ and 800℃，the [Mo]eq of β phase is in the [Mo]eq range of α+β and metastable β alloy type respectively. After being quenched in water, the β phase occurs martensitic transformation at 850℃ and retains metastable β phase at 800℃。