马氏体式相变过程中所引起的内耗变化

用扭摆测量两种跌锰合金(Mn17.5％和12.8％)和一种铜铝合金(Al13％)的内耗,在发生正和反的马氏体相变的温度范围内各出现一个内耗峰。这种内耗峰出现的条件是必须伴随着马氏体式相变过程的进行。用含Mn17.5％的铁锰合金作了系统实验,观察到内耗峰的高度随升温(或降温)速度和应力的增加而增高,随振动频率和含碳量的增加而减低。可以用振动一周内试样中转变量愈多内耗也愈大的关系得到统一的解释。讨论了关于产生内耗峰的机构。认为主要由于马氏体相变是突然间完成,此时扭转的外力可视为常数,从应力和不均匀物质交互作用能的计算,可以证明外力所做的功必须损失一半,因而引起内耗。此外应力感生相变也可以引起很小一部分内耗。

THE BEHAVIOR OF INTERNAL FRICTION ASSOCIATED WITH THE PROCESS OF MARTENSITE-TYPE TRANSFORMATION

Internal friction in two kinds of iron-manganese alloy which contain Mn 17.5% and Mn 12.8% respectively and one kind of copper-aluminum alloy containing 13% Al were measured with a torsion pendulum, and internal friction peaks were observed in the temperature range in which the martensite or reverse martensite transformation is taken place. The condition for the appearance of this internal friction peak is that it occurs only when accompanied by the process of martensite-type transformation.Systematic observations were made with iron-manganese alloy containing 17.5% Mn, and it was found that the height of internal friction peak increases with the increase of the rate of heating (or cooling) or the stress, decreases with the increase of the frequency of vibration or the carbon content in the specimen. All these may be explained by the reason that the more the amount of new phase has transformed in one period of vibration, the larger is the internal friction.The mechanism of the internal friction peak was discussed. The conclusion was reached that because of the suddeness of the formation of martensite, the applied external forces due to torsion pendulum may be considered as constant during the time of formation for martensite plates, and since half of the work done by the external forces during the alteration must be lost as confirmed by the calculation of interaction energies between stresses and iuhomogenities, it consequently gives rise to the substantial portion of internal friction. On the other hand, the stress-induced phase transformation also gives rise to a minor portion of internal friction.