稀土元素对铁的内耗的影响

本文对稀土元素含量(铈和镧含量的总和为:0,0.011,0.026,0.037,0.075,0.124％)不同的工业纯铁样品,在充分去碳、氮后进行了内耗测量。结果指出:铁的晶界激活能随稀土元素含量的变化出现极大值。这个极大值出现在稀土元素含量约0.03％左右,其值为11.3×10⁴卡/克分子,比不含稀土元素的铁样品(6.4×10⁴卡/克分子)约高一倍。对渗碳样品进行内耗测量得出:晶界内耗峰较充分去碳、氮样品的晶界内耗峰有近30℃的较大移动,各样品的晶界激活能趋近相等为7.6×10⁴卡/克分子(实验误差在±2000卡/克分子以内)。对碳在铁中的斯诺克峰的测量得出:随铁中稀土元素含量的增加,峰的高度被降低,而峰的位置和铁的比较,并没有变化。对各样品的冷加工内耗测量得出:未去碳和氮的原始样品(断面缩减率为88％)的冷加工内耗峰出现在230℃附近,峰值随稀土元素含量的增加而显著降低。对样品充分去碳、氮以后再重新渗氮,并进行冷加工(断面缩减率为88％),则冷加工内耗峰出现在190℃,这个峰也随着稀土元素含量的增加而显著降低。本文对于铁的这三个内耗峰(晶粒间界峰,斯诺克峰,冷加工峰)随着稀土元素含量而发生变化的可能原因,进行了初步的讨论。

EFFECT OF RARE EARTH ELEMENTS ON THE INTERNAL FRICTION OF IRON

Internal friction measurements were made on commercial iron specimens containing various amounts of cerium and lanthanum (combined content: 0, 0.011, 0.026. 0.037, 0.075, 0.124%). For specimens thoroughly treated with wet-hydrogen to remove carbon and nitrogen impurities, the activation energy associated with the grain boundary internal friction peak was found to vary with the content of cerium and lanthanum. A maximum appears around the content of 0.03%. The maximum activation energy is 11.3×10⁴ calories per mole and is about twice the value for iron free from cerium and lanthanum (6.4×10⁴ calories per mole). For specimens loaded with carbon, the grain boundary internal friction peak was found to appear at a temperature 30℃ higher than that of the specimen free from cerium and lanthanum. The activation energy associated with the grain boundary peak was found to be 7.6×10⁴ calories per mole (experimental error is within ±2000 calories per mole) and is approximately independent of the cerium and lanthanum content.Measurements on the Snoek peak associated with carbon in iron showed that the height of the peak decreases with an increase of the content of cerium and lanthanum, whereas the position of the peak remains unaltered as compared with that of iron specimen free from cerium and lanthanum.The cold-work internal friction peak of the original iron specimen containing carbon and nitrogen was found to appear around 230℃ (with the specimen cold-worked to 88% reduction in area), and this peak was considerably lowered with an increase of the cerium and lanthanum content. After the specimens were fully treated with wet-hydrogen and then loaded with nitrogen, the cold-work peak (with the specimen cold-worked to 88% reduction in area) was found to appear around 190℃. This peak was also considerably lowered with an increase of the cerium and lanthanum content.Preliminary discussions were made on the possible origins of the effect of the addition of rare earth elements on the three internal friction peaks (grain-boundary peak, Snoek peak, cold-work peak) of iron.