在铁铬铝电热合金中加入0.038％镧铈混合稀土或0.49％钇与不加稀土金属的共三种试样,进行快速寿命和氧化动力学的对比试验,对氧化后试样氧化膜的形态和粘附性进行了金相观察。X射线衍射分析结果发现:含钇的试样在1200℃经350小时氧化后,在氧化膜的内层存在一个新相。初步鉴定这一新相是钇铝石榴石(Y_3Al_5O_(12)),它与氧化膜粘附性的明显改善有着直接的关系。 铁铬铝合金在高温下长时间停留,晶粒迅速长大,力学性能急剧降低。稀土金属特别是钇的加入,有效地阻止晶粒长大,显著地减缓力学性能的降低,这可能是稀土元素能够大幅度提高铁铬铝电热丝快速寿命值的主要原因。
To ascertain the effect of rare earth additives on the quality of Fe-Cr-Alelectric heating alloy, the rapid heating life test and oxidation kinetics studyof three specimens: (A)-plain alloy, (B)-added 0.038％ La-Ce mixture, and (C)-added 0.49％ Y, have been examined. The observations of morphology andadhesivity of the oxidized layer reveal that in the interior of specimen C afterexposed for 350 hours under 1200℃, a new phase which has been identified asyttrium-aluminium-garnet (Y_3Al_5O_(12)) was present. This might have a direct in-fluence upon the adhesivity of the surface oxidized layer. In the case of the plain alloy, exposure at high temperatures gave rise tograin growth with rapid deterioration in the mechanical properties of the speci-men. The addition of rare earth, especially of yttrium, was found to be effec-tive in preventing crystal growth and therefore exerted correspondingly goodinfluence upon the mechanical properties of the specimen at high temperatures.Such may be the reason why the rapid heating life of alloys with the additionof rare earth is longer than without.
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