Measurement of Instantaneous Dislocation Velocities in Iron

进行了位错速度和相关的可移动位错密度的原位测量。这些测量是在金属晶体在普通拉伸测试中变形时进行的，是基于电子与移动位错的内在相互作用。这种相互作用可以通过在旋转磁场的存在下使晶体变形而改变，从而导致变形应力的变化。应力变化的角度由磁场矢量相对于移动位错的空间方向决定。测量角度可以确定在普通拉伸试验中移动位错的位错速度。相对于变形晶体的主动滑移系统的磁场的选择性对准和旋转允许确定边缘和螺旋位错速度。这些位错速度测量是作为应力和温度的函数进行的，确定了瞬时位错速度如何随这些参数变化。位错速度和可移动位错密度也被测量为应变速率变化的函数。这些实验提供了铁晶体变形时的瞬时位错速度和可移动位错密度的测量。这一信息目前对于材料的塑性变形是未知的，并提供了铁晶体中第一个这样的测量。＊＊＊

9703993 Galligan In situ measurements of dislocation velocities and the associated mobile dislocation density are performed. These measurements, carried out while a metal crystal is deforming in an ordinary tensile test, are based on the intrinsic interactions of electrons with moving dislocations. The interaction can be varied by deforming a crystal in the presence of a rotating magnetic field, resulting in a change in the deformation stress. The change in stress occurs at an angle determined by the spatial orientation of the magnetic field vector relative to the moving dislocations. Measurement of the angle establishes the dislocation velocity of the mobile dislocations during an ordinary tensile test. Selective alignment and rotation of the magnetic field relative to the active slip system of the deforming crystal allows the determination of edge and screw dislocation velocities. These dislocation velocity measurements are carried out as a function of stress and temperature, establishing how the instantaneous dislocation velocity varies with these parameters. Dislocation velocities and mobile dislocation densities are also measured as a function of changes in the strain rate. %%% These experiments provide measurements of instantaneous dislocation velocities and mobile dislocation densities in iron crystals while they are deforming. This information is presently unknown for the plastic deformation of materials and provides the first such measurement in iron crystals. ***