摘要
分析了含稀土 Nd 的5621STi 合金氧化形成的近球状复合氧化突出物在恒温氧化和冷却过程中所受应力。突出物所受生长应力通过周围合金的塑性变形大部分得以释放,而热应力却来不及释放而保持下来。这一热应力充分大,导致那些形体较大的突出物剥离基体或碎裂。即与通常起“钉扎”效应的稀土氧化突出物不同,含 Nd 的钛合金氧化形成的上述类型的突出物在冷却过程中起着氧化膜内裂纹初始发生点的作用。氧化后试样表面形貌观察以及氧化膜拉伸撕裂实验验证了上述分析。
The stresses forcing on the sphere-like intrusions during the isothermaloxidation and cooling have been analyzed.These intrusions mainly composed of Nd_2O_3 andTiO_2 form when Nd doped 5621S alloy is oxidized.The calculation indicates that most of thegrowth stress is released by plastic deformation of the alloy near the intrusion,however thethermal stress is maintained.This thermal stress is great enough to cause the large intrusions tospaU or break.So these large intrusions can serve as points of initial cracking,which differs from“pegging effect”of those RE-rich oxides.The observation of surface morphology of the oxidescale and the tensile test measuring the adhesive of the oxide scale verify the analysis mentionedabove.
关键词
氧化
氧化膜
钛合金
稀土元素
ND
oxidation
oxide cracking
stress analysis
oxide intrusion
5621S Tialloy
