抄録
The stress dependencies of the internal friction and Young’s modulus of cold-rolled and low-temperature-annealed specimens of α-copper alloys (mainly Cu-Zn alloys) were investigated at the frequencies of about kilocycle and at room temperature. It was found that there are two kinds of critical stresses; the one is the first critical stress beyond which a remarkable increase of the internal friction and a remarkable decrease of Young’s modulus begin to take place simultaneously, and the other is the second critical stress beyond which the internal friction and Young’s modulus do not change reversibly with the stress applied. The former corresponds with the micro yield point and the latter with the macro yield point. The “spring limit” or ”Federungsgrenze” is a little larger than this second critical stress. When a specimen is cold-rolled after annealing the internal friction increases and the first critical stress does not increase as the tensile strength. However, after low temperature annealing,the critical stress of a cold-rolled specimen increases remarkably, and this increament increases with the increasing concentration of solute atoms up to the solubility limit. These phenomena are discussed in terms of dislocation model.
