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设计并采用激光熔炼工艺制备出镍基固溶体γ增韧的Mo_2Ni_3Si三元金属硅化物合金。差式扫描量热分析(DSC)及高温金相实验表明,该合金共晶温度约1287℃,液相线温度约1355℃。研究了该Mo_2Ni_3Si合金在炉冷、水冷及激光表面熔凝条件下的凝固组织。结果表明,在炉冷及水冷条件下,随着凝固冷却速度的提高,合金中Mo_2Ni_3Si初生枝晶体积分数降低、二次枝晶臂间距减小,但激光表面快速熔凝合金中Mo_2Ni_3Si初生枝晶体积分数急剧增加(62％)。激光表面快速熔凝γ/Mo_2Ni_3Si合金由于组织细小,且基体γ相被Mo及Si元素过饱和固溶,具有最优异的力学性能(显微硬度600HV);炉冷Mo_2Ni_3Si合金凝固组织初生枝晶上分布着许多显微裂纹,且显微组织为粗大的二相组织,力学性能较差。
A series of Mo_2Ni_3Si ternary metal silicide alloys with Ni-based solid solution γ toughened were designed and fabricated by laser melting process. Differential scanning calorimetry (DSC) and high temperature metallography experiments show that the alloy has a eutectic temperature of about 1287 ℃ and a liquidus temperature of about 1355 ℃. The solidification structure of the Mo_2Ni_3Si alloy was studied under the condition of cold, water cooling and laser surface melting. The results show that with the increase of solidification cooling rate, the volume fraction of primary dendrites in Mo_2Ni_3Si decreases and the distance between secondary dendrite arms decreases. However, the primary dendrites of Mo_2Ni_3Si in the laser rapid solidification alloy The number of points increased sharply (62%). Due to the fine microstructure and the supersaturation and solid solution of matrix γ phase by Mo and Si elements, the most excellent mechanical properties (microhardness 600HV) of γ / Mo_2Ni_3Si alloy are rapidly melted on the laser surface. The primary dendrites on the solidified microstructure of furnace-cooled Mo_2Ni_3Si alloy Distribution of many micro-cracks, and the microstructure of coarse two-phase structure, poor mechanical properties.