冷却速度对快速凝固Ti-48Al-4Cr合金组织转变规律及力学性能研究

Effect of cooling rates on microstructures evolution and nanohardnessof rapidly solidified Ti-48Al-4Cr alloy

摘要:

采用单辊旋淬快速凝固设备制备了不同辊速条件下的Ti-48Al-4Cr(at.%)薄带,研究冷却速度对快速凝固Ti-48Al-4Cr合金的组织及力学性能变化规律。结果表明,快速凝固Ti-48Al-4Cr合金凝固在辊速为10m/s和20m/s时,基体为等轴的γ相,基体中含有少量的B2相、α₂相颗粒和片层组织；辊速进一步增加至30m/s时,基体转变为α₂相,片层组织消失。快速凝固Ti-48Al-4Cr纳米硬度随着冷却速度的增加而增加,纳米硬度由常规凝固时的5.04±0.09GPa增加至辊速为30m/s时的10.48±0.13GPa。该结果为研究TiAl合金组织转变,减小TiAl合金偏析,提高其力学性能提供了基础。

Abstract:

In this work the effect of cooling rates on microstructure of Ti-48Al-4Cr(at.%) alloy rapidly solidified at different wheel speeds were experimentally investigated by using the single roller melt-spinning technique. The results indicate that after rapid solidification at the wheel speed of 10m/s and 20m/s, the microstructures mainly consist of equiaxed γ phase, few volume fraction of α₂, B2 phase particles and lamellar structures exists in the γ phase matrix. At the wheel speed of 30m/s, the matrix changes to α₂ phase and the lamellar structures disappear. The nanohardness increases with the cooling rate increasing. It enhances from 4.98±0.10GPa under normal pressure to 7.48±0.16GPa under 4GPa. The nanohardness increases from 5.04±0.09GPa of conventional cast Ti-48Al alloy to 10.48±0.13GPa of rapidly solidified Ti-48Al-4Cr alloy with the wheel speed of 30m/s. This research has provided the basis of further studying on the microstructures, reducing the segregation and enhancing the mechanical properites of TiAl alloy.