电沉积宽晶粒度分布纳米镍的组织结构与力学性能研究

Microstructures and Mechanical Properties of Electro- deposited Nanocrystalline Ni with Broad Grain Size Distribution

摘要:

通过直流与脉冲电沉积分别制备平均晶粒度为20~30 nm，宽晶粒度分布（5~120 nm）的纳米镍。在室温静拉伸应变速率范围内，直流电沉积制备的纳米镍的平均抗拉强度和平均断裂延伸率分别为1176 MPa与10.6%。而由脉冲电沉积技术制备的纳米镍抗拉强度可达1500 MPa之上，最高断裂延伸率可达13.3%。与电沉积获得的普通窄晶粒度分布的纳米镍相比，宽晶粒度分布的纳米镍的塑性要高出100%以上。其原因是大型晶粒内部允许位错的存在，且理论计算表明，晶内位错可通过Frank-Read源机制进行增殖。

Abstract:

The flawless nanocrystalline (nc) Ni with a broad grain size distribution ranging from 5 to 120 nm and an average grain size of 20-30 nm were prepared by direct current and pulse electrodeposition, respectively. In the region of room-temperature static tensile strain rates, for the nc Ni prepared by direct current electrodeposition, the average ultimate tensile strength and the average elongation to failure are 1176 MPa and 10.6%, respectively. While for the nc Ni prepared by pulse electrodeposition, the ultimate tensile strength exceeds 1500 MPa and the max elongation to failure reaches 13.3%. In contrast to the typical electrodeposited nc Ni with a narrow grain size distribution below 50 nm, the ductility is increased by more than 100% for the present nc Ni samples. This enhancement can be interpreted by the reason that dislocations can exist and multiply in the large grains by the mechanism of Frank-Read source in the plastic deformation process revealed by theoretical calculation.