Brittle-ductile transitions in polycrystalline tungsten

• Published in: Philosophical magazine (Abingdon, England) Vol. 90; no. 30; pp. 3947 - 3959
• Main Authors: Giannattasio, A., Yao, Z., Tarleton, E., Roberts, S.G.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 28.10.2010; Taylor & Francis
• Subjects: Activation energy; Applied sciences; Bars; brittle-ductile transition; Cross-disciplinary physics: materials science; rheology; Deformation, plasticity, and creep; dislocation; Ductile brittle transition; Elasticity. Plasticity; Exact sciences and technology; fracture; Fractures; Materials science; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Miniature; Physics; plasticity; purity; Sintering; Strain rate; Treatment of materials and its effects on microstructure and properties; Tungsten; Dislocation motion; Experimental data; Notched test piece; Polycrystal; Mechanical properties; Two dimensional model; Ductile brittle transition; Sintering; Tungsten; Plasticity; Stress effects; Crack tip; Activation energy; Impurity states; Strain rate
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786435.2010.502145

The strain rate dependence of the brittle-to-ductile transition (BDT) temperature was investigated in notched and un-notched miniature bars made of high-purity polycrystalline tungsten and in notched bars of less-pure sintered material. The activation energy, E BDT , for the process controlling the BDT in pure tungsten was equal to 1.0 eV both in un-notched and notched specimens, though the brittle-ductile transition temperature, T BDT , was ≈ 40 K lower at each strain rate for the un-notched samples, indicating that the activation energy, E BDT , is a materials parameter, independent of geometrical factors. The experimental data obtained from pure tungsten are described well by a two-dimensional dislocation-dynamics model of crack-tip plasticity, which is also discussed. For sintered tungsten, E BDT was found to be 1.45 eV; T BDT at a given strain rate was higher than in the pure tungsten by ≈ 90 K, suggesting that the BDT in tungsten is very sensitive to impurity levels.