Co对CuNiSi合金应力松弛行为的影响

Effects of Co on the Stress Relaxation Behavior of CuNiSi Alloy

采用悬臂梁弯曲应力松弛测试方法对CuNiSiCo合金的应力松弛性能进行了测试,利用TEM探究Co对CuNiSi合金应力松弛组织的影响,并建立了应力松弛模型。结果表明,应力松弛过程可动位错密度是降低的经验公式σ*=[K′ln(t+a0)+C]-n的模拟结果,与实验结果基本相符;合金松弛分为2个阶段,第一阶段应力松弛速率较大,由于在应力松弛的初期阶段,可动位错数量很多,位错移动的阻力比较小,位错移动的驱动力比较大;第二阶段,应力松弛速率较小,处于缓慢松弛阶段,这一阶段位错与杂质原子以及位错与第二相粒子发生交互作用,使位错增殖;Co在Cu中的固溶度较小且易于与空位结合,从而抑制了调幅分解形成所需的空位移动,致使含Co元素的CuNi-Co-Si铜合金空位大量减少,抑制了可动位错的滑移;另一方面,促进了基体中析出相的析出,析出相弥散均匀地分布在合金基体中,在发生应力松弛过程中,移动的可动位错在遇到弥散分布的第二相之后,会被第二相所钉扎,故Co替代部分Ni形成的CuNiSiCo合金的应力松弛性能要优于CuNiSi合金。

The CuNiSiCo alloys relaxation could be divided into two stages and stress relaxed fast in the first stage while slowly in the second stage and tended to a certain limit value after a long time. During the first stage, there are many the movable dislocations, and dislocation resistance to movement is relatively small. The driving force of the dislocation movement is relatively large, so the stress relaxation rate is larger in the first stage of the stress relaxation. In the second stage, dislocations with the impurity atom and the second phase particle interactions could lead to dislo- cation multiplication, and the emergence of cross-slip. The stress relaxation values of the CuNiCoSi alloy are smaller than the CuNiSi alloy. The first reason is replacement of Ni with Co, and Co suppressing spinodal decomposition to form the desired vacancies movement and promotion of （Ni, Co, ）2 Si phase precipitation, resulting in suppression of the dislocation slip movement. On the other hand, the precipitates were promoted in the Cu-Ni-Co-Si alloy. The pre- cipitate phase uniformly distributed in the grain boundaries and the matrix, during the relaxed condition, and the dislo- cations moving was blocked by the precipitates.