2023 年 62 巻 1 号 p. 23-28
Changes in the microstructure of Cu–Ni–Si alloys in which Ni was partially or totally substituted by Co were investigated. Based on the results obtained, the effects of changes in the amount of Co substitution on precipitation hardening and work hardening were discussed. The size of precipitates in the peak–aged alloys became smaller as the amount of Co substitution was increased. The theoretical value of precipitation hardening (σp) estimated from the size of the precipitates increased in proportion to the amount of Co substitution. In addition, the estimates of σp decreased with increasing rolling reduction. Thus, it is suggested that the precipitates were sheared by dislocations during cold rolling and partially redissolved into the Cu matrix. The decrease in precipitation hardening associated with the redissolution of precipitates during cold rolling became smaller as the amount of Co substitution increased. The effect of Co substitution on the redissolution of precipitates can be theoretically explained in terms of the size and misfit strain of the precipitates. The sum of σp and the estimated value of dislocation hardening became larger as the amount of Co substitution increased and the trend was consistent with the measured value.
