电沉积纳米镍薄板的超塑微拉深性能

采用脉冲电沉积工艺制备了厚度为0．1mm的纳米镍薄板，在不同的温度和应变速率下对该薄板进行单向拉伸试验，确定了其超塑性变形的最佳工艺条件，在此基础上进行了纳米镍薄板的微拉深性能实验。实验结果表明：纳米镍薄板的微拉深性能随成形温度的升高而提高；在温度为723K、半球形拉深凸模直径为1mm、拉深速度为1～5mm／min的条件下，均可成功拉深出半球件。采用透射电镜和扫描电镜对拉深变形前的沉积态组织和拉深变形后的微观组织进行了观察比较，结果表明，微拉深后大部分镍晶粒长大到微米量级。根据实验结果，初步探讨了超塑微拉深的主要变形机制。

Superplastic Micro Deep Drawability of Nanocrystalline Nickel Sheet Fabricated by Electrodeposition

The nickel sheets with a thickness of 0.1mm were prepared by pulse electrodeposition process. To determine the optimum processing parameters relevant to micro deep drawing, uniaxial tensile tests were carried out at different temperatures and strain rates. Biaxial forming was subsequently performed. It is indicated that the micro deep drawability depends obviously on test temperature, and the chance of fracturing during micro deep drawing decreases with the increasing temperature. The nickel thin sheet can be readily drawn successfully using a hemispherical punch with diameter of 1mm at 723K and punch rates ranging from 0. 1mm/min to 5mm/min. TEM and SEM were also used to examine microstructures of the as-deposited nickel sheet and deformed nickel specimens. After micro deep drawing most nickel grains grow to be micro scale. The deformation mechanisms of nanocrystalline nickel sheet during micro deep drawing be will be discussed herein.