凝固条件对γ-Ni/MO_2Ni_3Si合金凝固组织的影响  

Effect of Solidification Conditions on Microstructure and Mechanical Properties of γ-Ni/Mo_2Ni_3Si Alloy

作　　者：徐亚伟[1] 王华明[1] 

机构地区：[1]北京航空航天大学材料学院激光材料加工与制造技术实验室,北京100083

出　　处：《中国激光》2007年第3期427-431,共5页Chinese Journal of Lasers

基　　金：国家杰出青年科学基金(50625413);航空基础科学基金(05H51009)

摘　　要：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。γ-Ni toughened Mo2Ni3Si ternary metal silicide alloy was designed and fabricated by the laser melting deposition process. Differential scanning calorimetry （DSC） and high-temperature microscopic analysis indicated that the Mo2 Ni3Si alloy has an eutectic temperature of 1287 ℃ and a liquidus temperature of 1355 ℃. In this paper, the solidification microstructures of γ/Mo2 Ni3 Si alloy under furnace cooling, water cooling and laser surface remelting conditions were studied. Results showed that under furnace cooling and water cooling conditions, the volume fraction of Mo2Ni3Si primary dendrite and the secondary dendrite arm spacing decreased with increasing cooling rate. However, for the alloy under laser surface remelting condition which had the highest cooling rate （-10^3 K/s）, the volume fraction of Mo2 Ni3 Si primary dendrite increased markedly to about 62 %. Due to its finest structure, the laser surface remelted γ/Mo2 Ni3 Si alloy possessed the optimum mechanical property （600HV）, while many microcracks were observed on the Mo2 Ni3 Si primary dendrite for the furnace cooled Z/Mo2 Ni3 Si alloy and its coarse dual-phase structure was much unfavourable to mechanical property.

关 键 词：激光技术 金属硅化物 凝固 冷却速度 显微硬度 

分 类 号：TN249[电子电信—物理电子学] TG111[金属学及工艺—物理冶金]