阳极氧化对TiAl合金高温氧化行为和力学性能的影响

采用电化学阳极氧化技术在含NH4F的乙二醇电解液中对TiAl合金进行阳极氧化处理。研究阳极氧化对TiAl合金高温氧化行为和力学性能的影响。结果表明:由于“卤素效应”,阳极氧化处理的TiAl合金经高温氧化后表面形成致密、连续的Al₂O₃氧化膜,有效阻止了氧的内扩散,进而显著提高合金的抗高温氧化性能。经1000℃氧化100 h后,阳极氧化试样增重由未经阳极氧化处理试样的85.86 mg/cm²降至0.67 mg/cm²。另一方面,阳极氧化TiAl合金表面硬度和弹性模量随高温氧化时间延长呈先降低后升高的趋势。阳极氧化TiAl合金在高温服役后,合金的摩擦系数较未经阳极氧化处理试样上升,但表面耐磨性先降低后升高。这是由于TiAl合金经阳极氧化后,表面形成了一层富铝含氟氧化膜,由于氧化膜中F元素在高温氧化过程中与Ti、Al结合形成卤化物,卤化物蒸气选择性扩散在原始氧化膜处形成致密的Al₂O₃保护膜。阳极氧化对TiAl合金力学性能的影响主要是由于氧化膜中Al₂O₃的含量变化所致。

Effect of the anodization on high tempreture oxidation behavior andmechanical properties of TiAl alloy

TiAl alloy was electrochemically anodized in ethylene glycol electrolyte containing with NH4F to prepare anodic film.The influence of anodization treatment on the oxidation behavior and mechanical properties of the anodized TiAl alloy were then characterized.Results shown that based on the halogen effect a continuous and dense Al₂O₃ oxide scale will generate on the anodized TiAl alloy after high temperature oxidation.After oxidation at 1000℃for 100 h,the weight gain of the anodized TiAl alloy was dramatically decreased from 85.86 mg/cm² to 0.67 mg/cm².Moreover,it is shown that the surface hardness and elastic modulus of the anodized TiAl alloy decreased first and then increased with the prolonging of oxidation time.Meanwhile,the friction coefficient of the anodized TiAl alloy increased comparing to the bare TiAl alloy.The surface wear resistance of the anodized TiAl alloy exhibited similar phenomena.This is because that during high temperature oxidation process,aluminum fluorides selectively transport to the surface through pores or micro-cracks,and are oxidized to Al₂O₃ at the surface region.The influence of anodization treatment on the mechanical properties of the anodized TiAl alloy is attributed to the Al₂O₃ content contained in the oxide scale.