一种新型镍基变形高温合金“孪晶+γ′相”组织调控及高温力学性能研究

摘要:

本研究采用形变热处理的方法在新型镍基变形高温合金中构筑了“孪晶+ γ′相”复合结构,并结合EBSD和SEM探讨了孪晶与γ′相的演变规律。同时,研究了合金在760 ℃下的高温力学性能。结果表明,“孪晶+ γ′相”复合结构可以有效改善合金的高温力学性能,且随着退火孪晶长度分数的增加,孪晶片层厚度增加,材料的高温强度呈降低的趋势；当轧制态合金(ε=68%)在1120 ℃退火15 min并进行双级时效处理(650 ℃/24 h/AC和760 ℃/16 h/AC)后,“孪晶+ γ′相”复合结构中退火孪晶的长度分数为25.38%,γ′相的平均尺寸为32.21 nm,此时,合金的屈服强度从固溶态的775 MPa提高到了1184 MPa,断后伸长率从3.18%提高到了18.96%。通过构筑“孪晶+ γ′相”复合结构可以有效提高合金的高温力学性能,这为高温力学性能的提升提供了一种新策略。

Abstract:

In this study, the "twin + γ′ phase" composite structure was constructed in a novel Ni-based wrought superalloy by means of thermomechanical treatment, and the evolution of twin and γ′ phases was investigated by using EBSD and SEM. Meanwhile, the high temperature mechanical properties of the alloy at 760 ℃ were studied. The results show that the "twin + γ′ phase" composite structure can effectively improve the high temperature mechanical properties of the alloy, and with the increase of the length fraction of the annealing twin, the thickness of the twin lamellar increases, and the high temperature strength of the material decreases; When the rolled alloy (ε=68%) is annealed at 1120 ℃ for 15 min and subjected to two-stage aging treatment (650 ℃/24 h/AC and 760 ℃/16 h/AC), the length fraction of twins in the "twin + γ′ phase" composite structure is 25.38% and the average size of γ′ phase is 32.21 nm. The yield strength of the alloy increased from 775 MPa to 1184 MPa, and the elongation after fracture increased from 3.18% to 18.96%. By constructing the "twin + γ′ phase" composite structure can effectively improve the high-temperature mechanical properties of the alloy, which provides a novel strategy for improving the high-temperature mechanical properties.