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通过熔模精密铸造制备不同厚度的Ti-48Al-2Cr-2Nb和Ti-48Al-2Cr-2Nb-0.25TiB2合金铸板,研究冷却速率和TiB2添加对合金凝固组织和力学性能的影响.实验结果表明,当凝固速率从37增加至2×102 K/s时,合金的凝固路径并未发生改变.基体合金的晶粒从650细化至300μm,Ti-48Al-2Cr-2Nb-TiB2合金的晶粒则从550细化至80μm.随着冷却速率从37提高至2×102 K/s,基体合金的片层间距从360减小至30 nm,TiB2添加对片层间距的影响较小.在中等冷却速率下(69 K/s),Ti-48Al-2Cr-2Nb-TiB2合金铸板表现出最优的力学性能,显微硬度达到HV 550,极限抗拉强度达到570 MPa,这主要归因于晶粒尺寸、片层间距的细化和细小TiB2颗粒的作用.从冷却速率、成分过冷和添加硼化物等角度对显微组织演化过程进行详细讨论.“,”Effects of cooling rate and 0.25 at.％ TiB2 addition on solidification microstructure and mechanical properties of Ti-48Al-2Cr-2Nb alloys fabricated by the investment casting with different thicknesses were studied. The results show that with the cooling rate increasing from 37 to 2×102 K/s, the solidification path of the studied alloys is unchanged. The grain size of the matrix alloy is refined from 650 to 300 μm, while the grain size of Ti-48Al- 2Cr-2Nb-TiB2 is reduced from 550 to 80 μm. The lamellar spacing of matrix alloy is reduced from 360 to 30 nm with increasing the cooling rate from 37 to 2×102 K/s, while TiB2 addition shows little refinement effect on the lamellar spacing. Ti-48Al-2Cr-2Nb-TiB2 sample under medium cooling rate (69 K/s) exhibits superior microhardness (HV 550) and ultimate tensile strength (570 MPa) among the studied alloys. The refined grain size, lamellar spacing and fine TiB2 particles could account for the favorable mechanical properties of the studied TiB2-containing alloy. The microstructure evolution was discussed in light of cooling rate, constitutional supercooling and borides addition.