Precipitation phase evolution of a new third-generation Ni-based single crystal superalloy containing osmium
The application of Re and Ru in Ni-based single crystal superalloys is often limited by their content and phase stability,and it is important to search for new elements that can replace Re and Ru at the same time.In this study,a new type of Ni-based single crystal superalloy with high content of Os was designed,the cast single crystal alloy was prepared by the traditional Bridgman technique,and the alloy was subjected to solution aging treatment,the precipitation phase evolution of the alloy was investigated by optical microscopy and scanning electron microscopy.The results show that Os and W in the as-cast alloy segregate in the dendrite core region,while Al,Ta,and Ti segregate in the inter-dendritic region,even after a long time of solution heat treatment,there is still a slight segregation of Os and W.Due to the elemental segregation in the dendritic region,the γ′ phase in the inter-dendritic region is more likely to be transformed into a cubic shape than that in the dendrite core after the primary aging treatment,and the secondary aging treatment can slightly increase the size and volume fraction of the precipitated phase,and transform the shape from cubic to round.
Ni-based single crystal superalloyelement segregationdendritesolution heat treatmentaging treatmentγ′ precipitate
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