微量增强体对TC18钛基复合材料微观组织的影响

Effects of trace reinforcements on microstructure of TC18 Ti matrix composite

摘要:

使用真空自耗炉制备出多种微量TiB和TiC增强的Ti-5Al-5Mo-5V-1Fe-1Cr钛基复合材料,增强体在热处理过程中可大幅细化β相,但是细化幅度却随着增强体含量的增加而变缓,文中揭示出这和增强体的Zener拖曳力变化有关,增强体含量增加而拖曳力增幅变缓。此外还研究了增强体对α相球化的作用,α球化率随着增强体含量增加而小幅波动,然而在其作用下,等温压缩过程中魏氏体群结构中的板条状α明显球化。等温压缩过程中,增强体对α球化的作用不同于热处理过程,微量增强体可以通过促进界面转变而加速球化。

关键词:TC18钛基复合材料; 微量增强体; α相球化; β相细化

Abstract:

Ti-5Al-5Mo-5V-1Fe-1Cr Ti matrix composites reinforced with different weight fractions of TiB and TiC are fabricated via a consumable vacuum arc-remelting furnace. The reinforcements can significantly refine β phase during heat treatment. However, the extent of the microstructure refinement decreases gradually with the increase of the reinforcements. It is revealed that the microstructural phenomenon is associated with Zener dragging force exerted by the reinforcements. The rate of increase of the dragging force tends to decrease with the increase of the reinforcements. Additionally, the effects of the reinforcements on the spheroidization of α are also investigated. The spheroidization rate of α fluctuates somewhat with increasing the trace reinforcements during heat treatment. Nevertheless, the reinforcements accelerate the spheroidization of α lath in the Widmannstatten structure obviously during isothermal compression. The effects of the reinforcements during isothermal compression are different from those during heat treatment. In addition to accelerating the diffusion significantly, the trace reinforcements also contribute to the spheroidization of α by accelerating interface transformation during isothermal compression.

Key words:TC18 Ti matrix composite; Trace reinforcement; Spheroidization of α; Refinement of β