硼含量及冷却速度对TiAl合金十字形铸件组织的影响

Influences of Boron Concentration and Cooling Rate on Structure of TiAl Alloy Crisscross Casting

摘要:

采用真空感应磁悬浮熔炼法制备Ti-47Al-2Cr-2Nb-xB (x=0,0.15,0.8,1.5) (at%)十字形不同壁厚(2、5、10、20 mm)的铸件。借助体视显微镜、扫描电子显微镜(SEM)对铸件的组织进行分析，研究硼含量和冷却速度对铸件硼化物形态、晶粒细化效果的影响。结果表明：硼含量越高，冷却速度越快，细化效果越好。随着硼含量的增加，硼化物的形态从弯曲条带状逐渐转变为短棒状或片状。Ti-47Al-2Cr-2Nb-0.8B铸件硼化物尺寸随冷却速度的降低而减小，Ti-47Al-2Cr-2Nb-0.15B和Ti-47Al-2Cr-2Nb-1.5B铸件硼化物随冷却速度的变化规律不明显

关键词:TiAl基合金;冷却速度;晶粒尺寸;硼化物

Abstract:

Ti-47Al-2Cr-2Nb-xB (x=0, 0.15, 0.8, 1.5) (at%) crisscross casting with different thickness (2, 5, 10 and 20 mm) were prepared by a vacuum induction skull furnace. Influences of the cooling rate and the boron concentration on the boride shape and the grain size of the casting were studied by means of stereo microscope and scanning electron microscopy (SEM). The results show that the higher boron concentration and the faster cooling rate lead to smaller grain size. Waved-flake borides change into stick- or plate-like ones when the boron concentration increases. Boride size of Ti-47Al-2Cr-2Nb-0.8B casting is reduced with the cooling rate decreasing, but the change of boride size of Ti-47Al-2Cr-2Nb-0.15B and Ti-47Al-2Cr-2Nb-1.5B casting is unobvious

Key words:TiAl based alloy; cooling rate; grain size; boride