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用低频扭摆的方法,系统地研究了能够较有把握地观测到在Al-0.5％Cu合金中所出现的反常位错内耗的实验程序。结果指出,把试样在拉力试验机上预先拉伸到某一适当的形变量后,立即测量它在某一适当温度下时效的过程中的内耗,可以在内耗-时效时间曲线上观察到一个表现反常振幅效应(即内耗-振幅曲线上出现一个峯值)的时效内耗峯。用经过充分时效而内耗已经达到稳定值的试样,逐渐增加振幅,测量内耗,也可以观察到一个应变振幅内耗峯(当内耗表示为应变振幅的函数时)。此外,用一定的应变振幅在较高温度下,测量经过充分时效的试样的内耗时,也可以观察到一个表现反常振幅效应的温度内耗峯(当内耗表示为温度的函数时)。这些实验结果肯定地指出,在一定测量温度下的振幅内耗峯和表现反常振幅效应的温度内耗峯是存在的。为了找出以前在Al-0.5％Cu中所观察到的反常内耗现象重复性不好的原因,系统地研究了测量内耗所用的应变振幅对于出现振幅内耗峯的影响以及预形变量对于出现时效内耗峯和温度内耗峯的影响。对于出现反常内耗现象的实验条件进行了分析。所观察到的关于反常内耗现象的实验结果,都可用位错拖着溶质原子气团运动的模型来作定性的解释。具体的模型和理论分析将另行报导。The experimental procedure for observing the low frequency anomalous internal friction peaks in Al-0.5% Cu alloy was systematically investigated in order to be able to obtain reproducible results. It is shown that, when the specimen is plastically deformed on a tensile testing machine to a suitable extent and then the internal friction measured in the course of aging at a suitable temperature, an aging internal friction peak exhibiting an anomalous amplitude effect may be observed. After the specimen has been "sufficiently" aged and its internal friction has reached a steady value, an amplitude internal friction peak at a given temperature can be observed when the strain amplitude for measuring internal friction is successively increased. Furthermore, when the internal friction of the "sufficiently" aged specimen is measured at higher temperatures with a given strain amplitude, a temperature internal friction peak exhibiting an anomalous amplitude effect may be observed. These experimental results demonstrated conclusively the existence of the previously observed amplitude internal friction peak at a given temperature and of the temperature internal friction peak exhibiting an anomalous amplitude effect.In order to find out why the anomalous internal friction peaks previously observed in Al-0.5% Cu alloy have a poor reproducibility, the effect of strain amplitude upon the appearance of the amplitude internal friction peak, as well as the effect of the amount of the previous plastic deformation upon the appearance of the aging internal friction peak and the temperature internal friction peak was systematically studied. An analysis was made on the experimental conditions for the appearance of these anamolous internal friction peaks.The observed experimental results concerning the anomalous internal friction peaks can be explained in a qualitative manner with a model in which the solute atom "atmosphere" was assumed to be dragged along with the dislocation. The concrete model and its theoretical analysis will be reported in a later paper.
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