Cu-Ni-Si合金二次时效时的再结晶行为

利用透射电镜、显微硬度法和电导率法,研究了Cu-Ni-Si二次时效过程中显微组织、硬度及导电率变化情况.结果表明:二次时效可使合金在较短的时效时间内获得更高的导电率,经预时效后冷变形的合金,溶质原子可借助密集且分布均匀的位错网络由铜基体快速传输至析出物处或析出物的形核部位完成析出过程,使铜基体得到快速的净化,从而获得较高的导电性.Cu-3.2Ni-0.75Si合金经预时效 变形后的时效过程中,可发生原位再结晶和不连续再结晶两种形式的再结晶.再结晶的形式主要决定于预时效时析出相的大小和冷变形的程度,稳定细小的析出相促使原位再结晶的发生,原位再结晶使合金微观组织中析出相比较细小,因而保持较高的硬度;亚稳的析出相在再结晶过程中将向稳定相转变,相变动力与形变储存能共同作用促使合金发生不连续再结晶,使合金硬度迅速下降,析出相快速粗化.

Recrystallization behaviour of Cu-Ni-Si alloy during two-step aging

In the case of two-step aging of Cu-Ni-Si alloy, the variation in microstructure, micro-hardness and electrical conductivity were investigated by TEM analyses, electrical resistivity and micro-hardness measurements. It is concluded that a higher electrical conductivity can be obtained by two-step aging treatment directly. The reason for this can be explained that the solute atoms of the alloy, which was cold rolled after pre-aging, could transmit from matrix to the precipitates or their nucleus easily through the path formed by the displacement networks which are distributed in the alloy homogenously and intensively. The situ recrystallization and discontinuous recrystallization can take place in Cu-3.2Ni-0.7Si for the effects of pre-aging combined with after-deformation-aging treatment. The result of the recrystallization in the aging process was dominated by both the size of pre-aging precipitation phase and the extend of cold deformation. It can be seen that a higher micro-hardness in the alloy corresponds to a microstructure with a fine and stable phase, which further promote the situ recrystallization taking place. However metastable precipitation phase formed during recrystallization will transform to stable phase and, in the case of discontinuous recrystallization affected by the combination of phase transformation kinetics and strain-energy, a rapid decreasing in micro-hardness corresponding to the coarse precipitation phase formed in the process will take place subsequently.