通过控制直流电解沉积电解液温度制备出不同微观结构的块体纳米孪晶Cu样品。结果表明,当电解液温度由313 K降低至293 K,纳米孪晶Cu的平均晶粒尺寸由27.6 μm减小至2.8 μm,平均孪晶片层厚度由111 nm减小至28 nm。电化学测试表明,降低温度减缓了纳米孪晶Cu沉积的电化学过程,使阴极过电位增大,引起晶粒和孪晶的形核率增加,从而使晶粒尺寸和孪晶片层厚度同时减小。

Nanotwinned (NT) metals are promising structural materials due to their excellent combination of strength and ductility. These superior properties are strongly dependent on the microstructures i.e. the twin length (grain size), the twin thickness and the twin orientation. Understanding the synthesis process and growth mechanism of NT metals is essential for their structure design. In this work, the effect of electrolyte temperature on the microstructures of highly oriented NT Cu samples, including twin thickness and twin length (grain size), are systematically studied. The NT Cu samples were prepared by means of the direct-current electrodeposition at 293, 298, 303, 308 and 313 K, respectively, while other deposition parameters such as current density, concentration of additive and pH value were kept constant. With decreasing the temperature from 313 K to 293 K, the average grain size decreases from 27.6 μm to 2.8 μm and the average twin thickness decreases from 111 nm to 28 nm, which results in an increment of hardness from 0.7 GPa to 1.5 GPa. This is because with decreasing the temperature, the overpotential of cathode for depositing metal elevates, leading to the nucleation rate of both the grain and twin enhanced.