Development of the Method for the Measurement of Single Crystal Elastic Constants from Polycrystalline Specimen

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The aim of the present research was to make an actuator for exerting a biaxial stress on a disk shaped specimen for X-ray diffractometer and utilize it for a method to determine the single crystal elastic constants from a polycrystalline specimen which is developed by Hayakawa et al. (J.Appl.Cryst.. (1985) 513-518).1. Manufacturing of an actuator of TiNi shape memory alloyA ring shaped actuator (inner diameter 18.5mm, outer diameter 22.5-28.5mm, thickness 4mm) was made of TiNi alloy. A aging treatment brought the Ms temperature below 0ﾟC and Af above room temperature. At a temperature near Ms, the inner diameter of a ring was expanded by inserting a tapered rod with a larger diameter. A disk shaped specimen was inserted in the expanded ring while keeping the temperature below Ms. A subsequent heating the ring and specimen above Af and cooling to room temperature bring the ring to the initial shape, and thus exerts a biaxial compressive stress on the inserted specimen. The applied stres … More s was obtained by the strain measured through a strain gage pasted on the specimen and Young's modulus.Different level of stress up to 250MPa could be obtained at room temperature by modifying the Ms and As temperature by changing the aging treatment and by using different thickness of the actuator.2. Measurement of single crystal elastic constants from a polycrystalline specimenOnce a few different levels of stress were applied on a polycrystalline specimens and the d-spacings from various reflections were obtained, the calculation of the single crystal clastic constants were straightforward following the recipe presented by the above mentioned paper. For an Fe-35wt%Ni, the following values were obtained :C_<11>=1.249 <plus-minus> 0.100, C_<12>=0.720 <plus-minus> 0.073, C_<44>=1.219 <plus-minus> 0.096 [10^5MPa]The results compare well with the constants obtained for an Fe-30Ni alloy from a single crystal (C_<11>=1.463, C_<12>=0.881, C_<44>=1.132 [10^5MPa]).An application for a cubic zirconia is in progress. Less