Abstract
The fractography of zirconium and zirconium alloy specimens cracked in a number of aggressive environments has been studied. In methanol-iodine at room temperature, fractures are completely intergranular, but penetration occurs even in the absence of applied stresses. In methanol-hydrochloric acid solutions, although intergranular attack on unstressed specimens also occurs, the application of external stress causes a change to transgranular cracking. When exposed in air at 300 to 450 C (572 to 842 F) with coatings of chloride salts or immersed in a fused nitrate-iodide salt mixture, cracking of stressed specimens is predominantly transgranular, whereas in fused nitrate-chloride and .nitrate-bromide salts at 300 to 450 C, the penetration is intergranular and occurs even on unstressed specimens with gross internal oxidation. Transgranular fractures can also be caused during dynamic bend tests in mercury and cesium. The transgranular fractures in methanol-hydrochloric acid; hot and fused salts; and liquid metals have characteristic differences. The mechanisms of both intergranular and transgranular failure are discussed.
