Plastic deformation of CVD textured tungsten — I. Constitutive response
The constitutive response of CVD textured tungsten in 〈001〉, 〈011〉 and random orientations under uniaxial compression subjected to a range of strain rates is investigated. Both 〈001〉 and 〈011〉 textured specimens revealed a strong strain rate sensitivity. The 〈001〉 specimens showed large ductility at all strain rates and significant strain softening during high strain rate deformation. The 〈011〉 texture undergoes homogenous deformation under quasi-static loading but failed prematurely due to extensive grain boundary cracking during high strain rate loading. The random orientation specimens exhibited brittle failure. The temperature rise during high strain rate deformation was measured using high speed infrared detectors. A physically based crystal plasticity model motivated by dislocation reactions in b.c.c. metals is outlined. The model predicts the dependence of constitutive response on the texture in tungsten polycrystals and suggests that the transverse tensile stresses which develop in 〈011〉 orientation due to the crystallographic asymmetry could be responsible for observed grain boundary cracking.
© 1993 Pergamon Press Ltd. Received 18 December 1992. The authors wish to acknowledge Professor A. J. Rosakis and Mr J. J. Mason for their help in making the high speed temperature measurements. G. Ravichandran would like to acknowledge the support of the National Science Foundation through a Presidential Young Investigator award.