温度和相结构对镧扩散动力学的影响

Effect of Temperature and Phase Constitution on Kinetics of Lanthanum Diffusion

研究了等离子体渗氮过程中La在密排六方ε Fe2～ 3N(ε)和面心立方γ′ Fe4N (γ′)双相中的扩散动力学规律。与γ′相或ε +γ′双相比较 ,发现ε相对La的扩散具有阻碍作用。一定温度下 ,随着渗氮时间的延长 ,ε相不断分解出γ′相 ;La在单相 (如γ′相 )和双相ε +γ′中的扩散深度分别呈抛物线和近似指数规律增加。提高渗氮温度 ,La扩散的深度增加 ,但其扩散动力学规律并未因此而改变 ;温度从 5 2 0℃升高至5

The diffusion of La in ε Fe 2～3 N(ε)and γ′ Fe 4N (γ′) phases formed by plasma nitriding was studied. It is found that with increasing nitriding time, the ε phase continuously decomposes into γ′ under employed experimental conditions. Comparing with γ′ phase or ε+γ′ ones, the mono phase ε has an impedient effect on La diffusion. La layer grows in the dual phases and mono phase follows an approximate exponential law and a parabolic one respectively and does not change with increasing temperature. Effect of increasing temperature in the range of 520 ℃ to 560 ℃ on La diffusion is less than that of phase constitution change such as decomposition of ε phase into γ′ one.