应变速率对电沉积纳米晶铜拉伸性能的影响

Strain rate effects on tensile properties of electrodeposited nanocrystalline Cu

采用直流电沉积工艺,制备了平均晶粒尺寸为56nm的致密纳米晶铜.室温下进行单向拉伸实验,发现纳米晶铜的强度和韧性均随应变速率的升高而增大,特别是韧性的速率敏感十分显著.应变速率由1.04×10-5s-1升至1.04s-1时,断裂应变由23.2%增至39.4%,同时抗拉强度由309MPa增至451MPa.这一现象可归因于两个方面:首先,纳米晶铜的应变硬化行为随应变速率的升高而增大,从而使其均匀变形阶段的应变增加;其次,高应变速率下纳米晶铜颈缩时发生晶粒转动,这有助于其失稳阶段的应变增加.

Fully dense nanocrystalline Cu with an average grain size of 56 nm was synthesized by a direct-current electrodeposition technique. Tensile tests performed at room temperature indicated that both the strength and the ductility of the nanocrystalline Cu increased by the increment of strain rate, especially a pronounced strain rate dependence of tensile ductility was observed. As the strain rate was raised from 1.04 ×10^5s^-1 to 1.04 s^-1, the fracture strain increased from 23.2 % to 39.4 %, and the ultimate tensile strength increased from 309 MPa to 451 MPa. Two reasons might be responsible for this phenomenon. First, the strain hardening behavior increased with increasing strain rate, resulting in an enhanced uniform elongation. Second, the collective grain-rotations were revealed when the nanocrystalline Cu necked at a higher strain rate, which contributed to the increase of strain after instability.