X-ray diffraction study of deformation by filing in B.C.C. refractory metals

Abstract

The b.c.c. refractory metals, niobium, tantalum, vanadium, chromium and tungsten, were cold worked by filing. The broadening of the powder pattern peaks was studied by Fourier analysis of the line shapes. The effective particle sizes, D _e(hkl), and root mean squared (r.m.s.) strains were measured in different crystallographic directions. Anisotropic values of particle sizes observed in tantalum and niobium were an indication of faulting in these metals. The degree of anisotropy of particle sizes was much smaller in vanadium; tungsten and chromium showed isotropic particle sizes. The ratio of r.m.s. strains may be calculated from the directional variation of Young's modulus. The absolute magnitude of r.m.s. strains was also computed for isotropic b.c.c. metals without faulting. The amount of faulting is observed to increase with the degree of elastic anisotropy of the b.c.c. metals of the group Vb. Metals of group VIb show no x-ray diffraction evidence of faulting.