EVALUATION OF ACCURACY IN THE ALCHEMI METHOD

An ALCHEMI measurement has been carried out to determine the crystallographic site of Co atoms in a Ti48.5Ni48.5Co3 shape memory alloy. The accuracy of ALCHEMI can be evaluated in terms of the r value, which is denoted by a difference in intensity between incident electron beams along Ti and Ni planes. In the present paper, the r value has been calculated as a function of crystal thickness, diffraction condition and accelerating voltage. It was thus found that the r value calculated without consideration of absorption effects did not explain experimental results. However, taking account of the absorption effects, it was quantitatively in good agreement with experimental results. It was also found that the r value increased with increasing accelerating voltage, the maximum value for 1 MV being about 2.5 times larger than that for 100 kV.