銅-鉄合金の高温時効に伴なう内部摩擦の変化について

Abstract

The changes in internal friction, hardness, electrical resistivity, magnetic properties and microscopic structure of 2.3, 5.4 and 9.6 wt% iron-copper alloys by aging at the temperatures from 600° to 750°C, were studied. During the aging process, the hardness change shows a single peak, while the electrical resistivity decreases in the stage of age-hardening and reaches an equilibrium state before the hardness reaches a maximum. In 2.3 wt% iron-copper alloys, there is no change of internal friction in the stage of age-hardening, but in the stage of over-aging, the internal friction increases remarkably. At the same time, the amplitude dependence appears and the break-away point shifts to the lower amplitude side with aging time. In the 5.4 and 9.6 wt% iron-copper alloys, the internal friction decreases in the stage of age-hardening and the change of internal friction in the stage of over-ageing is similar to that of the 2.3 wt% iron-copper alloys. The above change of internal friction in the stage of over-ageing begins at a shorter aging time with rising aging temperature and increasing iron concentration. This change of internal friction is related to the growth of the precipitate particles. Internal friction of copper-iron alloys in this study is neither a relaxation-type of energy loss nor a magnetomechanical hysteresis energy loss due to the precipitate, but it is a hysteresis energy loss of vibrating dislocation. On the basis of these results, the change of coherency between the matrix and the precipitate and hardening mechanism in these alloys have been discussed.