拉伸条件下镁合金第Ⅱ阶段加工硬化

Strain Hardening at Second Stage of Magnesium Alloy during Tension Process

在温度为25~100℃,应变速率为3×10^(-2)~3×10^(-3) s^(-1)范围内,对挤压态AZ31镁合金沿挤压方向进行拉伸试验,研究了第Ⅱ阶段加工硬化产生的条件及机理。结果表明,温度≤75℃,应变速率≥10^(-2) s^(-1),镁合金出现第Ⅱ阶段加工硬化,其加工硬化率为2 400~2 650 MPa。产生第Ⅱ阶段加工硬化的主要原因是,低温、高应变速率拉伸时,屈服应力升高,镁合金发生屈服时的初始位错密度及位错密度累积速率增加。当初始位错密度≥4.62×10^(16)m^(-2)时,镁合金出现第Ⅱ阶段加工硬化。

A tensile testing was carried out for extruded AZ31 magnesium alloy along extrusion direction at 25 ℃to 100℃,and strain rate from 3×10^-2^-×10^-3 s^-1.The generation condition and its mechanism of strain hardening at second stage were described.The results show that occurrence of strain hardening at second stage can be observed at temperature of below 75℃,and strain rate more than 10^-2 s^-1,where the strain hardening rate reaches up to 2 400-2 650 MPa,which is attributed to the increase of dislocation density and its accumulated rate due to yield stress increases when tensile testing was carried out at low temperature and high strain rate.The second stage strain hardening can be observed with dislocation density more than 4.62×10^16m^-2.