Inconel 617合金中第二相的析出规律研究

利用SEM和TEM对Inconel 617合金在700 ℃时效0~1 000 h后的M₂₃C₆碳化物和γ′-Ni₃(Ti,Al)相的析出规律及第二相析出对硬度的影响进行了研究。结果表明，700 ℃时效过程中样品在160 h时达到硬度峰值，且硬度的提高与晶界处析出的不规则M₂₃C₆碳化物、晶粒内部析出的棒状M₂₃C₆碳化物和球状γ′相有关，其中γ′相对材料的强化效果更明显。时效初期，第二相以M₂₃C₆碳化物为主，γ′相倾向在碳化物周围的富Al和Ti的区域形核长大。两种相互依附的析出相存在共格取向关系，限制彼此的生长。γ′相数量不断增多并向碳化物内部生长，导致碳化物逐渐分解。时效后期，晶粒内部的碳化物几乎消失，晶粒内部弥散分布着大量球状γ′相。根据实验结果，讨论了两种析出相的析出长大规律。

Precipitation Mechanism of Secondary Phase in Inconel 617 Alloy

The precipitation of secondary phase is important for the strengthening effects of the bulk materials. In this work, SEM and TEM were used to study the precipitation mechanisms ofM₂₃C₆ carbides and γ′-Ni3(Ti,Al), and their strengthening effects in Inconel 617 alloy aged at 700 ℃ for 0-1000 h. The results show that the hardness of the samples reaches the peak at 160 h during aging at 700 ℃. The increase of hardness is related to the precipitation of irregularM₂₃C₆ carbides at grain boundaries, the rod likeM₂₃C₆ carbides precipitated in the grains and the spherical γ′ phase. The strengthening effect of γ′ phase is more obvious than that ofM₂₃C₆ carbides in this material. At the early stage of aging,M₂₃C₆ carbides consume Cr atoms, leaving Ti and Al atoms to form Al and Ti rich region around the carbides. And then, γ′ phase nucleates at this region easily. The two types of precipitates have coherent orientation relationship with each other and with the nearby matrix. The γ′ particles precipitate around theM₂₃C₆ carbides dependently, limiting the growth of the two types of precipitates and resulting in the irregular shape of γ′ particles andM₂₃C₆ carbides at the early stage of precipitation. The number of γ′ phases increases and grows to the interior of carbides, resulting in the gradual decomposition of carbides. After longer time of aging, the carbides only distribute on the grain boundaries, the carbides disappear in the interior of grains, and high number of spherical γ′ particles can be observed homogeneously in the matrix. Based on the experimental results, the precipitation and growth mechanisms of γ′ particles andM₂₃C₆ carbides were discussed.