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研究了微量元素B、Y和冷却速度对Ti-47Al-2Cr-2Nb合金组织的复合细化效果。结果表明,在水冷铜坩埚磁悬浮真空感应熔炼和Y2O3型壳精密铸造条件下,B元素能够有效细化Ti-47Al-2Cr-2Nb铸件的晶粒尺寸,使其由粗大的柱状晶变为细小的等轴晶组织,但没有起到细化片层间距的明显作用。B、Y复合细化可以在B元素细化效果的基础上进一步细化片层团尺寸,同时显著细化片层间距。在壁厚为2～20mm范围内,Ti-47Al-2Cr-2Nb-0.8B-0.3Y铸件的宏观组织均为等轴晶;且随着厚度的增加,等轴晶尺寸逐渐增大。适当降低型壳预热温度也有助于获得细小的片层组织。
The effects of trace elements B, Y and cooling rate on the microstructure refinement of Ti-47Al-2Cr-2Nb alloy were studied. The results show that the element B can effectively refine the grain size of Ti-47Al-2Cr-2Nb castings from coarse columnar crystals to fine ones under the condition of water-cooled copper crucible with vacuum induction melting and Y2O3 shell casting. Equiaxed grain structure, but did not play a significant role in refining sheet spacing. B, Y composite refinement can be based on the refining effect of B elements to further refine the lamellar size, while significantly refining the lamellar spacing. In the range of 2 ~ 20mm, the macrostructure of Ti-47Al-2Cr-2Nb-0.8B-0.3Y castings are equiaxed. And as the thickness increases, the equiaxed grain size increases gradually. Properly lowering the shell preheat temperature also helps to obtain fine lamellae.