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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。
In the temperature range of 25 ~ 100 ℃ and strain rate of 3 × 10 ~ (-2) ~ 3 × 10 ~ (-3) s ~ (-1), the extruded AZ31 magnesium alloy was extruded in the direction of extrusion Tensile test, the second stage of work hardening conditions and mechanism. The results show that when the temperature is less than or equal to 75 ℃ and the strain rate is more than or equal to 10 ~ (-2) s ~ (-1), the second phase of the magnesium alloy appears to be work - hardened with a work hardening rate of 2400 ~ 2650 MPa. The main cause of the second-stage work-hardening is that at low temperature and high strain rate, the yield stress increases and the initial dislocation density and the cumulative rate of dislocation density at yielding of the magnesium alloy increase. When the initial dislocation density ≥4.62 × 10 ~ (16) m ~ (-2), the second stage of work hardening of magnesium alloy occurs.