Effect of La on non-metallic inclusions in FeCrAl alloy
In order to study the influence of rare earth La addition on the type and distribution of inclu-sions in FeCrAl alloys,based on thermodynamic analysis,the three-dimensional morphology and com-position of inclusions were observed and analyzed by SEM-EDS,and the size and quantity of inclu-sions were statistically analyzed.The results show that single Al2O3 only inclusion exists in FeCrAl al-loy at 1 600 ℃.During the solidification process,with the increase of the solid fraction in the system,AlN precipitates at the solidification front.After adding 0.009 3％La,Al2O3 transforms into LaAlO3.When the addition amount of La is 0.037 8％,the type of inclusions is LaAlO3+La2O2S,and the number of inclusions increases significantly.As holding time prolongs,the proportion of La2O2S gradually in-creases.When the addition amount of La is 0.096 4％,the proportion of La2O2S is further increased.After 60 min of heat preservation,single La2O2S only inclusion exists stably in the steel.The particle size of the inclusions is significantly affected by the aggregation properties of the inclusions.In the samples containing single LaAlO3 only at 1 600 ℃ for 60 min,LaAlO3 shows a strong tendency to ag-gregate in the early stage of the incubation,and average particle size of the inclusions firstly increases from 2.34 μm to 3.31 μm,and then decreases to 1.93 μm.The tendency of La2O2S to aggregate is weak.In the samples containing La2O2S,average particle size of inclusions is small and uniform,in the early stage of heat preservation,average particle size of inclusions remains in the range of 1.8-2.0 μm.
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