晶粒细化对Fe-Cr、Ni-Cr合金氧化行为的影响

EFFECT OF GRAIN-SIZE REDUCTION ON OXIDATION BEHAVIOR OF Fe-Cr AND Ni-Cr ALLOYS

采用机械合金化法制备块体纳米晶Fe-20Cr、Ni-20Cr合金,并研究其在1000℃空气中的氧化行为.结果表明:由于晶粒细化,加快了Cr向合金表面的扩散速度,增加了活泼组元Cr氧化物的形核位置,降低了Fe-Cr、Ni-Cr合金形成单一连续Cr2O3氧化膜所需的临界Cr浓度,故机械合金化Fe-20Cr、Ni-20Cr合金氧化后形成了单一的Cr2O3外氧化膜,且氧化速率明显小于普通晶粒大小的熔炼Fe-20Cr、Ni-20Cr合金.

The oxidation behavior of Fe- 20Cr and Ni- 20Cr alloys prepared by casting and mechanical alloying respectively, was studied at 1000℃ in air. Both of the cast Fe - 20Cr and Ni - 20Cr alloys formed complex scales, while the mechanically alloyed Fe - 20Cr and Ni - 20Cr alloys formed a single Cr2O3 scale. The oxidation rates for the cast alloys were higher than those of the corresponding mechanically alloyed alloys. The differences in the scale and the oxidation rate are attributed to that the grain- size reduction may enhance the diffusivity of solute Cr in the alloy and increase the nucleation sites of Cr2O3, and thus reduce the critical concentration of Cr for the formation of a Cr2O3 scale.