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高铌TiAl合金的铸态组织,粗大不均匀,有少量B_2相,长条状硅化物和硼化物沿晶界析出,使合金的室温塑性强度和断裂韧度降低。研究了均匀化处理和循环热处理等热处理方式对Ti-45Al-8Nb-0.5W-0.8B-0.2Si组织的影响。结果表明,采取均匀化处理,随炉加热到1 200℃,保温24h,空冷,再循环热处理,快速加热到1 150℃,保温4h,空冷,循环3次可获得理想的显微组织。
The as-cast microstructure of the high niobium TiAl alloy is coarse and inhomogeneous with a small amount of B 2 phase. The long strip silicide and the boride precipitate along the grain boundaries, which decreases the room temperature plasticity and fracture toughness of the alloy. The effects of heat treatment such as homogenization and cyclic heat treatment on the microstructures of Ti-45Al-8Nb-0.5W-0.8B-0.2Si were studied. The results showed that the ideal microstructure was obtained by homogenizing, heating in the furnace to 1 200 ℃ for 24h, air cooling, reheating, rapid heating to 1 150 ℃, holding for 4h, air cooling and recycling for 3 times.