Subsurface gradient of residual stress and lattice parameter in mechanically polished tungsten measured using classical X-rays and synchrotron radiation

Data obtained for tungsten sample using MGIXD method (Cu Kalfa radiation, 4 different incident angles)) and ED diffraction with synchrotron radiation. In the used MMXD method [28], the residual stress analysis is based on the ED synchrotron X-ray diffraction measurement performed for multiple hkl reflections. To do this, data were collected for one constant 2θ angle with the white synchrotron beam. Next, data were grouped for strictly chosen penetration depths in order to perform the residual stress analysis layer by layer in the sample and to get much deeper profile than in the case of the MGIXD method. 1. The complementary MGIXD and MMXD methods reveal a significant residual stress gradient present in the subsurface volume of a polished tungsten sample. The compressive stress of about -1000 MPa was determined very close to the polished surface (MGIXD method). Going deeper in the subsurface volume the residual stresses gradually decrease down to zero value at the depth of about 10 μm (MMXD method). 2. The value of lattice parameter remains constant (in the margin of 0.001Å) up to 9-10 μm of the depth, regardless the method used to determine it. 3. The results obtained using classical MGIXD for sample surface are continued by the MMXD results. High energy synchrotron radiation allowed measurements for significantly larger subsurface depths in comparison with a classical laboratory X-rays. 4. The MMXD with synchrotron radiation allowed to determine depth-dependent stress profile with spatial resolution of 1 µm, which is much better than in the case of standard ED measurements. 5. Almost isotropic elastic properties of tungsten crystallites simplifies analysis of the residual stress state.采用多掠入射角X射线衍射（MGIXD）方法（使用Cu Kα辐射，设置4种不同入射角）以及同步辐射能量色散（ED）衍射，获得了钨样品的测试数据。在所采用的多层深度X射线衍射（MMXD）方法[28]中，残余应力分析基于针对多个hkl晶面反射开展的同步辐射ED衍射测量实现。该方法通过固定2θ角并利用白色同步辐射光束采集数据，随后针对严格选定的穿透深度对数据进行分组，以实现样品内部逐层的残余应力分析，且可获得相比MGIXD方法更深的应力分布剖面。 1. 互补的MGIXD与MMXD测试方法揭示了抛光钨样品亚表面区域存在显著的残余应力梯度：采用MGIXD方法在紧邻抛光表面处测得约-1000 MPa的压应力；随着向亚表面深部延伸，残余应力逐渐降低，在约10 μm深度处降至零（该结果由MMXD方法测得）。 2. 无论采用何种测试方法，在深度达9~10 μm的范围内，晶格参数的波动均控制在0.001 Å的误差范围内，基本保持恒定。 3. 经典MGIXD方法获得的样品表面测试结果，可与MMXD方法的测试结果形成有效衔接。相较于传统实验室X射线测试，高能同步辐射可实现更大深度的亚表面区域测量。 4. 采用同步辐射的MMXD方法可实现空间分辨率达1 μm的深度相关应力分布表征，其性能远优于标准ED衍射测量。 5. 钨晶粒近乎各向同性的弹性特性，简化了残余应力状态的分析流程。