硅对Fe/Al固态扩散反应中Fe_2Al_5生长动力学的影响

Influence of silicon on growth kinetics of Fe_2Al_5 during reactive diffusion between solid iron and aluminum

采用Fe/Al-Si扩散偶的方法,利用SEM-WDS,研究了550℃硅在Fe/Al固态扩散反应中对Fe2Al5生长动力学的影响。实验结果表明,铝中硅含量不超过1.5 wt%时,扩散层中只出现Fe2Al5相,其生长动力学符合抛物线关系,实验测定的铁和铝在Fe2 Al5中的综合扩散系数(D)在含硅量(wt%)分别为0、0.5、1.0和1.5时,分别为3.46×10-15、2.61×10-15、1.28×10-15和0.86×10-15 m2/s。随硅含量增加,其抑制Fe2 Al5相生长速度的效果明显加强。当铝中Si含量为2%和3%时,首先出现Fe2 Al5相。随扩散时间的延长,在Fe2Al5相靠近Al-Si的一侧依次出现了τ1/τ9和τ5相,化合物层生长速度明显加快。由于部分硅以三元化合物的形式存在,导致硅的抑制作用下降。

The effect of silicon on the growth kinetics of Fe2Al5 during reactive diffusion at 550 ℃ between iron and aluminum was studied using Fe /Al-Si diffusion couples by means of scanning electron microscopy（SEM） and wave dispersive spectrometer（WDS）.It is found that only Fe2 Al5 intermetallics is observed in diffusion layer and its kinetics curves obey a parabolic growth law in Al-Fe-Si system with the content of silicon less than 1.5 wt%.With the experiment,the interdiffusion coefficient D of iron and aluminum in Fe2 Al5 is evaluated to be 3.46 × 10-15,2.61 × 10-15,1.28 × 10-15 and 0.86 × 10-15 m2 /s when the content of silicon is 0,0.5,1.0 and 1.5 wt%.The prohibiting ability to the growth of Fe2 Al5 is obviously intensified when the content of silicon is increased.When the Si was added to 2.0 and 3.0 wt% in Al,the first formed phase is Fe2 Al5.In the later stage,the τ1 /τ9 and τ5 phase is formed in Fe2 Al5 phase near Al-Si layer side.Simultaneously,the growth rate of the compounds will be accelerated.Because of some silicon exists as ternary compounds,the prohibiting ability to the growth of Fe2 Al5 will be evidently reduced.