空位与P原子对铁Σ3(111)晶界拉伸和剪切变形行为的影响

采用分子动力学方法建立了含0.5%、1%和1.5%P原子或空位的铁Σ3(111)晶界的原子结构模型,并对其拉伸和剪切变形行为进行了计算分析。结果表明,在相同条件下,不同空位和P原子含量(0.5%、1%和1.5%)的Σ3(111)晶界力学行为基本一致,力学性能略有差异。含1%空位的Σ3(111)晶界与无缺陷Σ3(111)晶界的拉伸应力-应变曲线基本一致。空位的存在使Σ3(111)晶界的剪切强度降低,在同一温度下,含1%空位Σ3(111)晶界的剪切强度均低于无缺陷Σ3 (111)晶界,含1%P原子的Σ3(111)晶界的抗拉强度远低于无缺陷和含1%空位的Σ3(111)晶界。在相同温度及相同P原子或空位含量时,P原子与空位初始间距(<14.18■)对Σ3(111)晶界的抗拉强度和伸长率具有一定的影响,但影响不大。在同一温度下,初始间距为2.03、6.08和10.13■的Σ3(111)晶界的剪切强度依次降低。P原子与空位的初始间距增大到14.18■时,空位对Σ3(111)晶界的影响弱化,P原子对Σ3(111)晶界的影响增大,使晶界剪切强度升高。

Model of critical strain for dynamic recrystallization in 10%TiC/Cu-Al_2O_3 composite

Using the Gleeble-1500 D simulator, the hot deformation behavior and dynamic recrystallization critical conditions of the 10%Ti C/Cu-Al2O3(volume fraction) composite were investigated by compression tests at the temperatures from 450 °C to 850 °C with the strain rates from 0.001 s-1 to 1 s-1. The results show that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow true stress-strain curves of the composite, and the peak stress increases with the decreasing deformation temperature or the increasing strain rate. The thermal deformation activation energy was calculated as 170.732 k J/mol and the constitutive equation was established. The inflection point in the lnθ-ε curve appears and the minimum value of-(lnθ)/ε-ε curve is presented when the critical state is attained for this composite. The critical strain increases with the increasing strain rate or the decreasing deformation temperature. There is linear relationship between critical strain and peak strain, i.e., εc=0.572εp. The predicting model of critical strain is described by the function of εc=1.062×10-2Z0.0826.