时效对一种沉淀强化型奥氏体耐热钢组织与性能的影响
陈纪杉，丁青青*，郝炜倩，徐诚雄，邹 南，魏 晓，张 泽，贝红斌*
(1. 浙江大学 材料科学与工程学院，浙江 杭州 310027；2. 浙江大学 硅材料国家重点实验室，浙江 杭州 310027)
摘 要 Fe-(24-30)Ni-(13-16)Cr-(1.5-3.5)Al-(1.2-2.8)Ti-(0-2)Mo-(0.02-0.2)C是一种由Ni3(Al, Ti)（γ′）强化的奥氏体耐热钢，高温性能优异；该耐热钢不含Ta、Nb等较为贵重的合金元素，在高端制造领域具有广阔的应用前景。拟服役温度和超温服役时的组织和性能稳定性是评估这类材料服役寿命的必要数据。本文利用先进电子显微学技术研究了耐热钢Fe-29Ni-14Cr-3Al-2.25Ti在拟服役温度680 ℃和超温服役温度750 ℃时效过程中显微组织的变化，并结合拉伸试验揭示了不同温度下时效对材料力学性能的影响。结果表明，在680 ℃时效过程中，合金的晶粒度变化较小，晶界处逐渐析出少量Ni2AlTi和σ相，γ′相的体积分数几乎不变，且时效对拉伸强度影响不大，但晶界σ相的析出可能导致合金更易沿晶界发生开裂，合金的断裂延伸率随时效时长增加而降低。750 ℃时效过程中晶粒度同样没有明显变化，晶界上析出大量Ni2AlTi和σ相，且晶内析出Ni2AlTi相，随着时效时间增加，Ni2AlTi和σ相的体积分数增加，而晶粒内部γ′相体积分数减少，合金的室温和高温强度不断降低，室温拉伸延伸率不断下降而高温拉伸延伸率不断上升。
关键词 时效；析出强化；显微组织；力学性能
中图分类号：TG146.1；TG115.21+5.3
文献标识码：A Doi:10.3969/j.issn.1000-6281.2025.06.001
Aging effects on the microstructure and mechanical property of a precipitation-strengthened austenitic stainless steel
CHEN Jishan 1，DING Qingqing 1*，HAO Weiqian1，XU Chengxiong1，ZOU Nan1，WEI Xiao1，ZHANG Ze1,2，BEI Hongbin1*
(1. School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027; 2. State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang 310027)
Abstract Fe-(24-30)Ni-(13-16)Cr-(1.5-3.5)Al-(1.2-2.8)Ti-(0-2)Mo-(0.02-0.2)C is a austenitic heat-resistant steel strengthened by Ni3(Al, Ti) (γ′) precipitates, exhibiting excellent high-temperature performance. This heat-resistant steel does not contain expensive alloying elements such as Ta and Nb, and has broad potential applications for the manufacturing field. The stability of the microstructure and properties at both service and over-temperature conditions are essential for evaluating the service life of such materials. This study employs advanced electron microscopy techniques to investigate the microstructural changes of the heat-resistant steel Fe-29Ni-14Cr-3Al-2.25Ti during aging at temperatures of 680 ℃ and 750 ℃ and effects of aging on mechanical properties of the alloy are revealed in combination with tensile tests at room temperature and 680 oC. The results indicate that aging at 680 ℃has little influence on the alloy’s grain size and the γ′ volume fraction, but a small amount of Ni2AlTi and σ phases precipitate at the grain boundaries. Moreover, aging at 680 ℃ has little effect on the tensile strength, but slightly decrease the elongation to fracture (EF) due to the precipitation of the σ phase along grain boundaries. During aging at 750 ℃, the grain size similarly shows no significant change. A large amount of Ni2AlTi and σ phases precipitates at the grain boundaries, while Ni2AlTi also forms within grains. As the aging time increases, the volume fraction of Ni2AlTi and σ phases increases, while the volume fraction of γ′ phase inside the grains decreases, therefore leads to changes in mechanical properties. The aging effects on the mechanical properties are discussed based on the deformation microstructure and fracture analysis.
Keywords aging; precipitation-strengthened steel; microstructure; mechanical property
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