A Novel Method for Shape Analysis: Deformation of Bubbles During Wire Drawing in Doped Tungsten

摘要

A novel technique has been developed for monitoring shape and size of microscopic pores, bubbles, second phase particles in deformed PM materials. The anisotropic small angle neutron scattering (ASANS) measurement provides direct visualisation of the shape of second phase objects after rolling, swaging, wire drawing. Also in case of mixture of different objects e. g. uniformly elongated bubbles and spherical ones they can be separated and their morphological parameters like relative number density, diameter, aspect ratio can be obtained from the quantitative analysis of ASANS data. Rods and wires from K-Al-Si doped tungsten containing residual porosity and K filled bubbles were studied from 6 mm to 0.2 mm in diameter. The increase of the average aspect ratio (～1/d) was found to be much slower than expected from the usual theory (～1/d~3). nstead of "constant volume" assumption, the "constant length" seems to be reliable. The ASANS investigation revealed also the occurrence of a small amount of spherical bubbles after several steps of wire drawing.