X-RAY STRESS ANALYSIS ON SINGLE CRYSTAL BY USING IMAGING PLATE

用二维X射线探测器成像板测量了单晶试件或多晶试件中任意单个颗粒的应力。一个问题是如何在实验上测量应力，因为在多晶样品的虚构DS圆上，没有测量到连续的DS衍射环，而是只出现了来自颗粒的一个光点。因此，对测量晶格间距的光斑进行校正是很重要的，我们采用了成像板和摆动的样品，因为它很容易在虚环上获得可测量的衍射斑。制备了经过处理的纯铁样品，在用Laue法测量了每个晶面上的取向(Hkl)[Uvw]之后，用Cr-Kalpha X射线测量了塑性变形前后每个晶面上的211个衍射。带有Phi和Psi旋转附件的样品台在样品表面的X射线照射点沿RX-ry方向振荡，利用两个步进电机将衍射点转换为可测量的圆弧。此外，为了精确确定成像板与样品之间的距离，还在同一成像板上对退火铁粉制成的DS环进行了衍射，利用成像板的曝光时间不到3分钟，并借助图像处理技术精确地确定了晶格间距。由塑性变形前后的晶格间距可以确定应力张量，而由塑性变形后的残余应力张量确定应力张量。由于两种张量之间的差异相对较小，我们得出结论，在无应力条件下，可以不使用晶格参数来测量颗粒中的残余应力。

Stresses in a single crystal specimen or any individual grain of polycrystals specimen were measured by the use of imaging plate which is a two-dimensional x-ray detector. A problem is how to measure stresses experimentally because continuous Debye-Scherror (DS) diffraction ring in not measured but only just a spot from a grain is appeared on an imaginary DS circle from polycrystals specimen. Therefore, it is important to correct such spot to be measured lattice spacing and we adopted the imaging plate and a specimen oscillating because it is easy to obtain a measurable diffraction spot on an imaginary circle.Course grained pure iron specimens were prepared and after determination of orientation (hkl) [uvw] on each grain measured by Laue method, 211 diffractions on each grain before and after plastic deformation were measured by Cr-Kalpha x-rays. A sample stage with the phi and psi rotating attachment was oscillated upon the x-ray irradiated point on the specimen surface in RX-RY directions by use of two stepping motors to convert a measurable arc from a diffraction spot. In addition, a DS ring from annealed iron powder was also diffracted on the same imaging plate for precise determination of the distance between imaging plate and specimen.Exposure time required for a diffraction pattern was less than 3 minutes by use of the imaging plate and the lattice spacing was accurately determined by the assistance of the image processing technique. We can determine both the stress tensor from the lattice spacing before and after plastic deformation and residual stress tensor from those after plastic deformation only. Since the difference between both tensors is comparatively small, we concluded that residual stresses in a grain can be measured without the use of lattice parameters on the non-stresses condition.