不同应变率下热压缩双辊轧制Mg-5.51Zn-0.49Zr合金动态再结晶的位错机制（英文）

Dislocation mechanism for dynamic recrystallization in twin-roll casting Mg–5.51Zn–0.49Zr magnesium alloy during hot compression at different strain rates

通过X射线衍射仪、光学显微镜和透射电镜研究Mg-5.51Zn-0.49Zr镁合金在热压缩实验中动态再结晶的位错机制。结果表明,当应变速率为1×10^(-3) s^(-1)时,由于位错攀移沿单一方向滑动,合金出现连续动态再结晶;当热压缩温度达到350°C、应变速率为1×10^(-2) s^(-1)时,由于位错发生滑移和攀移,合金出现连续动态再结晶;当热压缩温度达到400°C时,由于亚晶界弓出,合金出现不连续动态再结晶;当应变速率为1×100 s^(-1)时,合金出现连续动态再结晶是由于先导位错在堆积前发生攀移,导致位错在堆积过程中重新排列,形成位错差。一般来说,当应变速率增加时,位错攀移的主要影响机制由空位迁移转变为堆积前先导位错的压应力作用。

Dislocation mechanism operating in dynamic recrystallization （DRX） during hot compression of Mg-5.51Zn-0.49Zr alloy was investigated by X-ray diffraction, optical microscopy and transmission electron microscopy. The results showed that the continuous DRX occurred at a low strain rate of 1×10^-3s^-1, which was associated with the operation of the single gliding dislocation climbing. At the intermediate strain rate of 1×10^-2s^-1, the continuous DRX was associated with the climbing of the gliding dislocation array as deformed at an elevated temperature of 350 ℃, and in contrast, the discontinuous DRX was observed and associated with the bulging of subgrain boundaries as the deformation temperature was raised to 400 ℃. The continuous DRX was associated with the climbing of the leading dislocation ahead of pile-ups, and resultant rearrangement of misorientated flat dislocation pile-ups as the strain rate was increased to 1×100s^-1. It is suggested that the mechanism predominating the dislocation climbing was changed from the vacancy migration to the stress acting on the leading dislocation ahead of the pile-up as the strain rate was gradually increased.