稀土元素Y对TiNi形状记忆合金基体上的渗铝涂层恒温氧化行为影响

Effect of reactive element yttrium on the isothermal oxidation behavior of aluminide coatings on TiNi shape memory alloys

摘要:

采用粉末法,在不同Y含量的TiNi形状记忆合金基体上制备了650℃渗铝涂层,并对Y是如何影响涂层的形成以及涂层700℃恒温氧化性能进行了研究。结果表明渗铝涂层由外层TiAl₃和内层NiAl₃构成,涂层的生长主要由Al的内扩散控制。当Y含量低于1at.%时,稀土元素Y的添加促进TiAl₃外层的生长,抑制NiAl₃ 内层的生长。恒温氧化实验表明：添加0.5 at.%Y能明显降低渗铝涂层的氧化速度,但添加1 at.%Y和5 at.%Y却加速涂层的氧化。文中对Y是如何影响涂层的形成以及恒温氧化性能进行了分析。

Abstract:

Ti-Ni shape memory alloys with and without Y were aluminized at 650℃ using pack-cementation method. The influence of various amounts of Y addition on the microstructure and isothermal oxidation behaviors of aluminide coatings in air at 700℃ was investigated. The aluminide coatings exhibited double layer structure even the aluminization progress is mainly controlled by inward diffusion of Al. Addition of Y promotes the growth of outer TiAl₃ layer, but retards the growth of inner NiAl₃ layer when Y is below 1at. %. Isothermal oxidation result indicated that the addition of 0.5 at. %Y significantly reduced scale growth rate. In contrast, 1at. %Y and 5at. % Y addition significantly increased the oxidation rate, especially the latter. The effect of Y on the coating formation and the coating oxidation behavior was discussed in details.