利用性能测试、相分析、X射线及电子衍射、能谱分析,特别是扫描电镜观察析出相的三维形貌等方法研究了一种铁基高温合金750℃长期时效后组织结构对性能的影响。时效时间在200h以内,合金仍然具有令人满意的热强性和塑性。在时效1000h以内,γ′是稳定的;500h以后,开始有针状σ相析出;2000h后,σ相长大成片状,并有针状Laves相或μ相析出。发现TiC随时效时间的增长转变为Laves相。200h时效后持久强度开始下降,与针状σ相析出有关,但对高温塑性及持久塑性的影响不大。
The effect of microstructure on mechanical properties of an iron-base superalloy after prolonged exposure at 750℃ has been investigated by means of mechanical properties test, phase analysis, X-ray or electron diffraction, EDS and, especially, SEM observation on 3-dimensional morphology of the phases precipitated. After an exposure up to 200h, the high temperature strength and plasticity of the alloy are still satisfactory. The γ'-phase remained stable till 1000 h aging. The σ-phase was found as needle-like precipitates as a result of 500 h exposure, and it was then grown into plates, accompanied with the precipitation of Laves- or μ-phase after aged for 2000 h. As the exposure went on, TiC became the Lavesphase. It is regarded that the precipitation of the needle-like σ-phase is contributable to the decending of the high temperature endurance of the alloy aged for 200h, however, its high temperature plasticity and stress-rupture are little affected.
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