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用热重法研究了Ti ( 50± 2 )Al及Ti 4 8Al ( 1 ,4 )Cr等铸态TiAl基合金于 80 0℃静止空气中的循环氧化行为·结果表明 ,低Cr合金化TiAl的抗氧化性比二元TiAl的差·原因在于适量的Cr促进了TiAl表层原子的扩散 ,从而使氧化反应加速·因循环氧化而产生的应力疲劳使氧化物间的裂纹过早萌生、扩展并导致氧化层开裂 ,从而在通过致密膜进行固体扩散氧化反应的基础上引入了优先通过裂纹间隙进行气体短路扩散氧化的反应机制 ,最终使氧化程度加重 ,氧化规律表现为线性规律·氧化表面分层为 :二元TiAl表面呈富Ti/富Al交替的 (TiO2 +Al2 O3 )结构 ,三元TiAl Cr最外层则由纯R TiO2 晶体构成·
The cyclic oxidation behavior of as-cast TiAl-based alloys such as Ti (50 ± 2) Al and Ti 4 8Al (1, 4) Cr in still air at 80 ℃ was studied by TG method. The reason for the worse oxidation resistance than binary TiAl is that an appropriate amount of Cr promotes diffusion of TiAl surface atoms and accelerates the oxidation reaction. • Fatigue caused by cyclic oxidation causes premature initiation and propagation of cracks between oxides Oxide layer cracking, and thus through the dense membrane solid-state diffusion oxidation reaction based on the introduction of preferential cracks through the gas diffusion short-circuit diffusion reaction mechanism, the final increase in the degree of oxidation, the oxidation of the law showed a linear law * : The binary TiAl surface is rich in Ti / Al 2 O 3 structure, the outermost layer of ternary TiAl Cr is composed of pure R TiO 2 crystal ·