金属细丝扭转中的尺寸效应与钝化效应

Size and passivation effects in the torsion of thin metallic wires

本文对直径在25-50微米、有无钝化层的微尺度铜丝进行了扭转测试,开展了尺度效应与钝化效应的实验研究.通过磁控溅射制备了镀钛铜丝试样,在扭转测试中观察到直径减小和钝化层存在引起的屈服强度和流动应力的增加.与未钝化铜丝相比,钝化铜丝中存在更加明显的尺度效应,钝化铜丝的规范化扭矩随着直径减小而增加更为显著.基于Fleck-Hutchinson应变梯度塑性理论对铜丝的扭转响应进行了预测,数值结算结果与实验数据吻合较好,并阐明了钝化层对铜丝扭转变形影响的物理机制。

Torsion tests are performed on microscale copper wires of diameters ranging from 25 to 50μm,with and without passivation layers,to investigate the size and passivation effects.The copper wires coated with titanium are prepared by magnetron sputtering.An increase in the yield strength and flow stress arising from diameter reduction and the passivation layer is observed in the experiments.Compared with unpassivated wires,passivated wires exhibit more potent size effects.The normalized torque of passivated wires increases more significantly with the diameter decrease.The theoretical predictions based on the Fleck-Hutchinson strain gradient plasticity theory agree well with the experimental observations.The physical mechanism of the passivation layers affecting the torsional deformation of wires is elucidated.