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.
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.
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