The alloying effects on the microstructure, especially precipitation of harmful phases and solvus temperature of L1-structured γʹ phase, etc., are essential for alloy design and development of precipitation strengthened Co-based superalloys. Based on the newly reported Co30Ni9Al5Mo10Cr2Ta0.03B alloy, alloying elements Mo, Cr, Al, Ta and Ni are systematically changed and alloys are fabricated to investigate their microstructures in two heat treatment statuses, namely homogenization and aging, respectively. Results show that Mo and Cr are γ forming elements and have limited effect on γʹ solvus temperature, but high concentration of Mo and Cr facilitates the formation of harmful μ phase. Al, Ta, and Ni are all γʹ stabilizers and can effectively increase γʹ solvus temperature, but roles of Al, Ta and Ni are different. Increasing Al and Ta would result in other harmful phases, such as the μ phase in the 6Ta and 4Ta alloys, and μ + B2 phases in the 13Al and 11.5Al alloys. However, Ni addition significantly increases solvus temperature and area fraction of γʹ phase without occurrence of harmful phases. The current findings might provide guidelines for design and development of precipitation strengthened Co-based alloys.

中文翻译：

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合金元素对沉淀强化钴基高温合金显微组织的影响

合金化对显微组织的影响，特别是有害相的析出和L1结构γ′相的固溶线温度等，对于沉淀强化钴基高温合金的合金设计和开发至关重要。在新报道的Co30Ni9Al5Mo10Cr2Ta0.03B合金的基础上，系统地改变合金元素Mo、Cr、Al、Ta和Ni，并制备合金，分别研究其在均匀化和时效两种热处理状态下的显微组织。结果表明，Mo和Cr是γ形成元素，对γ′固溶线温度影响有限，但高浓度的Mo和Cr有利于有害μ相的形成。 Al、Ta、Ni都是γʹ稳定剂，可以有效提高γʹ固溶线温度，但Al、Ta、Ni的作用不同。增加Al和Ta会产生其他有害相，如6Ta和4Ta合金中的μ相，以及13Al和11.5Al合金中的μ+B2相。然而，Ni的添加显着提高了固溶线温度和γʹ相的面积分数，而没有出现有害相。目前的研究结果可能为沉淀强化钴基合金的设计和开发提供指导。