高强Ni-Co基变形高温合金中γ/γ'共格组织的热稳定性与力学性能研究

    Thermal Stability of γ/γ' Coherent Microstructure and Mechanical Properties of High-strength Ni-Co-based Wrought Superalloy

    • 摘要: 基于团簇成分式设计方法,结合高熵合金化原则,设计了一种新型Ni-Co基变形高温合金,其名义成分为Ni-Co-2.66Al-3.3Ti-1.37Nb-2.66Ta-12.29Cr-2.83Mo-5.41W-0.08C-0.02B-0.03Zr(wt%)。采用真空非自耗电弧炉制备合金铸锭,经1100℃/1 h固溶处理后,在850℃进行1000 h时效处理,并对时效态样品进行微观组织表征和力学性能测试。结果表明:合金微观组织表现为高体积分数(约54%)的方形γ'粒子均匀分布在FCC-γ基体中。经1000 h长时效后,γ'粒子表现出极低的粗化速率(K=0.26 nm3/s);合金硬度随时效延长变化不大(412~458 HV),进一步表明,γ/γ'共格组织具备优异的热稳定性。此外,时效50 h时合金的室温屈服强度达1090 MPa;800℃下仍保持900 MPa的屈服强度,展现出优异的力学性能。强化机制分析表明,优异的强度主要源于析出强化的显著效果(约724 MPa)。

       

      Abstract: A novel Ni-Co-based wrought superalloy with the nominal composition Ni-Co-2.66Al-3.3Ti-1.37Nb-2.66Ta- 12.29Cr-2.83Mo-5.41W-0.08C-0.02B-0.03Zr(wt%) was designed by employing the cluster formula approach combined with the high-entropy alloying principle. The alloy ingot was prepared by vacuum non-consumablevacuum arc melting, followed by solid-solution treatment at 1100 C for 1 h and subsequent aging treatment at 850 ℃ for 1000 h. The microstructural characterizations and mechanical property tests of the aged specimens were carried out. The results reveal a typical coherent γ/γ' microstructure characterized by a high volume fraction (about 54%) of cuboidal γ' nanoparticles that uniformly precipitated within the FCC-γ matrix. After prolonged aging for 1000 h, the γ' precipitates exhibit an extremely low coarsening rate(K=0.26 nm3/s), and the microhardness remains nearly unchanged (412 HV-458 HV), which demonstrates the exceptional thermal stability of the γ/γ' coherent microstructure. The alloy aged for 50 h achieves a yield strength of 1090 MPa at room temperature and retains a high yield strength of 900 MPa at 800 ℃, indicating outstanding mechanical performance. Quantitative analysis of the strengthening mechanisms shows that precipitation strengthening is the dominant contributor, accounting for approximately 724 MPa.

       

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