ESTUDO DO EFEITO SNOEK DEVIDO A OXIGÊNIO E NITROGÊNIO EM TUNGSTÊNIO UTILIZANDO UM PÊNDULO DE TORÇÃO

Abstract

The internal friction measurements have often been used for more than fifty years in the study of anelastic relaxations due to stress induced ordering of interstitials elements present in the group V metals with bcc structure. However, this study has not been extensive for group VI metals, as for example, tungsten. In this work, the internal friction and frequency measurements as a temperature function were made in tungsten samples with oxygen and nitrogen present in lhe metallic matrix. The samples were policrystals of tungsten, supplied by Aldrich Inc. These samples were measured using a torsion pendulum, operating in a temperature range between 300 and 700 K, with heating rate of 1.0 K/min, in a vacuum lower than 10-5 torr. The results have shown complex relaxation structures where were identified the relaxation processes due to the stress induced ordering of one oxygen and one nitrogen atom around tungsten atoms of lhe metallic matrix (W-O and W-N processes) and pairs of oxygen and nitrogen around tungsten atoms of the metallic matrix (W-O-O and W-N-N processes).