Abstract
The fatigue-creep deformation characteristics and evolutions of microstructure of P/M superalloy FGH96 widely used for the turbine disc of an aero-engine were investigated experimentally. The low cycle fatigue-creep tests with different holding times were performed at 550℃. The influence of the holding time on the stress-strain curve, cyclic strain response, fatigue-creep life and damage mechanism were discussed. The results reveal that the holding time has a significant effect on the fatigue-creep deformation characteristics. As the holding time increases, the hysteretic energy of inelastic strain rises, the steady-state hysteresis curve shifts to the right and the envelope strain and the envelope strain rate increase. Fatigue-creep life decreases firstly exponentially and then stabilizes. The creep damage gradually plays a leading role. The fracture analysis indicates that the introduction of the holding time makes the section appear as a multi-crack source. The fracture mode changes from transgranular fracture to transgranular-intergranular mixed fracture. The slip bands and a small amount of dimples appear in the crack propagation zone and the dimple characteristics of the transient fracture zone are obvious.
Highlights
疲劳-蠕变研究的一个重要方面,它反映了材料在 周期 反复载荷作用下的变形特性。 图 4 给 出 了 FGH96 合金在 550°C 条件下,保载时间分别为 1,5, 10,15,20,25 s 时的循环应力-应变曲线,取每个试 验的稳态循环应力-应变曲线进行对比分析。 发现 不同试验条件下各滞回曲线呈梭形,形状饱满,反映 出 FGH96 合金具有较强的塑性变形能力和耗能能 力。 材料的疲劳伴随着其内部能量的耗散,是一个 不可逆过程,这种变化必须通过外界提供能量才能 实现[24] 。 即裂纹扩展过程中会不断从外界吸收能 量,并通过裂纹张开所产生的迟滞回线面积进行表 征,当吸收的能量达到临 界能量值时材料就会断裂[25] 。 从图中可知,随着保载时间的增加,滞回曲 线向右偏移,滞回曲线所包围面积逐渐增大,说明保 载时间的增加使得滞回能逐渐增大,降低材料的疲 劳-蠕变寿命。
The fatigue⁃creep deformation characteristics and evolutions of microstructure of P / M superalloy FGH96 widely used for the turbine disc of an aero⁃engine were investigated experimentally
The low cycle fatigue⁃creep tests with different holding times were performed at 550°C
Summary
疲劳-蠕变研究的一个重要方面,它反映了材料在 周期 反复载荷作用下的变形特性。 图 4 给 出 了 FGH96 合金在 550°C 条件下,保载时间分别为 1,5, 10,15,20,25 s 时的循环应力-应变曲线,取每个试 验的稳态循环应力-应变曲线进行对比分析。 发现 不同试验条件下各滞回曲线呈梭形,形状饱满,反映 出 FGH96 合金具有较强的塑性变形能力和耗能能 力。 材料的疲劳伴随着其内部能量的耗散,是一个 不可逆过程,这种变化必须通过外界提供能量才能 实现[24] 。 即裂纹扩展过程中会不断从外界吸收能 量,并通过裂纹张开所产生的迟滞回线面积进行表 征,当吸收的能量达到临 界能量值时材料就会断裂[25] 。 从图中可知,随着保载时间的增加,滞回曲 线向右偏移,滞回曲线所包围面积逐渐增大,说明保 载时间的增加使得滞回能逐渐增大,降低材料的疲 劳-蠕变寿命。 工程科学学报, 2016, 38(2) : 248⁃256 ER Qiliang, DONG Jianxin, ZHANG Maicang, et al Fatigue Behavior of Powder Metallurgy Superalloy FGH97[ J] . Study on the Hot Deformation Behavior and Dynamic Recrystallization Behavior of FGH96 P / M Superalloy[ D] .
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