Application of Electron Fractography to the Study of High-temperature Cavitation in Tungsten

Because brittle fracture surfaces sometimes carry a clear imprint of the results of prior thermomechanical history of a material, electron fractography can be used to glean information on this history. This is particularly so for those high-temperature phenomena that involve the development of elimination of small holes in solids. Examples of such holes are sintering pores, creep cavities, and gas bubbles. If the matrix is brittle at low temperatures the holes can be exposed for detailed microscopic examination simply by snapping the specimen at low temperature. This requirement is satisfied in tungsten in which we have studied the crystallography and the growth rates of gas bubbles, the morphologies of creep cavities, and the mechanism of hot cracking in fusion welds.