Thermal activation analysis on the bubble-strengthening mechanism at high temperatures in tungsten fine wires

Grain-shape parameters for high-temperature creep resistance in powder metallurgy tungsten fine wires

“…7, was observed at Ͼ 40 MPa, giving H ϭ 180 ‫ע‬ 80 kJ/mol at the highest measurable stress. [6] On the other hand, no grain boundary cavitation could be confirmed at Ͻ 40 MPa, in which H increases to 390 ‫ע‬ 50 kJ/mol with decreasing stress, suggesting that the grain boundary diffusion (Coble creep) begins to play an important role in the deformation. [18] It is known that void growth increases as the oxygen content increases, and that a higher partial pressure of oxygen is required to cause void growth as the creep stress decreases.…”

“…[6] leads to ⅐ 3 ͌ ␥ ϰ 1/(d R) [7] If one estimates S/V to be roughly proportional to 1/d, Eq. Because the activation energy of H ϭ 390 kJ/mol obtained suggests the occurrence of diffusional creep at grain boundaries, Eq.…”

“…[2] The most likely mechanism by which bubbles strengthen the matrix is the so-called modulus-defect interaction. [5,6] On the other hand, most of the bubbles exist on grain boundaries and play a role in controlling the morphology of secondary recrystallized grains. [3] If the total interfacial energy is not at a minimum, the bubbles are nonequilibrium, their shape being irregular.…”