Development of Measurement Technique for Lattice Spacing at Strain Free by Neutron Diffraction Method
Toru SAITO, Nobuaki MINAKAWA, Yukio MORII, Toshihiko SASAKI and Yukio HIROSE
Abstract:For precise stress analysis of engineering materials by diffraction methods, lattice spacing of strain-free materials, d0, must be accurately measured and estimated. Powder diffraction method is a general way of determining the d0. However, preparation of high quality powder sample is actually difficult in that labor, time, knowledge, and technique are required. In this study, we propose a new easy technique of measuring the sample as original process material instead of the powder diffraction method for estimation of accurate d0. The d0 obtained by our technique is estimated from the dAve which is the average of d measured while turning the sample material at random. The strain-free lattice constant, a0, is calculated from dAve(hkl) of some diffraction planes by the extrapolation method. The d0(hkl) of each diffraction plane is converted from this a0. In own method, the d0(hkl) of the extra super duralumin which have the structure of the texture was measured. To examine ! The reliability of this new method, the d0(hkl) obtained by own method was compared with the d0(hkl) of powder estimated by the general methods which is neutron and X-ray diffraction method. These differences were 8.7~10-6 nm or less. These values become 10 Mpa or less for the stress. This result confirmed that present method could calculate d0(hkl) with enough accuracy for the neutron residual stress analysis. Key Words:Neutron diffraction, Strain-free, Lattice spacing, Extra super duralumin, Texture