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研究了Bridgman定向凝固技术制备的Ni-Si过共晶自生复合材料在不同凝固阶段时的组织特征、相的析出特征以及相组成。探讨了Ni-Si过共晶复合材料的晶体生长机制以及退火温度对亚稳相的影响。结果表明:未定向凝固时的组织呈树枝晶组织,定向凝固初始阶段组织相对粗大,随着热流逐渐趋于稳定,晶体沿最优生长方向生长,组织相对细小且生长稳定。非平衡凝固时Ni-Si过共晶组织包括α-Ni基体相,Ni-Ni_3Si共晶相和Ni_(31)Si_(12)亚稳相,亚稳相Ni_(31)Si_(12)的存在使Ni-Si过共晶合金的硬度增加,脆性增加。1100℃退火保温30 min后得到的显微组织中亚稳相Ni_(31)Si_(12)明显减少。Ni-Si过共晶组织中Ni相为非小平面相,Ni_3Si相和Ni_(31)Si_(12)相为小平面相。
The microstructure, phase precipitation and phase composition of Ni-Si hypereutectic self-composites prepared by Bridgman directional solidification at different solidification stages were studied. The crystal growth mechanism of Ni-Si hypereutectic composite and the effect of annealing temperature on the metastable phase were discussed. The results show that the microstructure of dendritic structure is dendritic microstructure, and the microstructure is relatively coarse at the initial stage of directional solidification. As the heat flux gradually stabilizes, the crystal grows along the optimal growth direction, and the microstructure is relatively small and stable. The Ni-Si hypereutectic structure in the non-equilibrium solidification includes the α-Ni matrix phase, the Ni-Ni_3Si eutectic phase and the Ni_ (31) Si_ (12) metastable phase and the metastable phase Ni_ (31) Si_ Ni-Si hypereutectic alloy increases the hardness, increased brittleness. The metastable phase of Ni 31 Si 12 was obviously reduced in the microstructure obtained after annealed at 1100 ℃ for 30 min. The Ni phase in the Ni-Si hypereutectic structure is a non-faceted phase, and the Ni_3Si phase and the Ni_ (31) Si_ (12) phase are faceted phases.