Stress corrosion failure of Zircaloy?2 sheets in methanolic HCl solution: Role of crystallographic texture

Abstract

The stress corrosion cracking (SCC) characteristics of Zircaloy?2 sheets in methanol?0.4 vol. pct. hydrochloric acid have been studied in the annealed and cold?rolled conditions using longitudinal and transverse specimens. The times to failure for annealed longitudinal specimens were longer than those for similarly tested transverse specimens at stress levels below ?45% UTS. The cold?rolled specimens developed resistance to SCC, but failed totally by cleavage when notched, unlike annealed specimens which failed by intergranular initiation followed by cleavage. The crystallographic texture developed by cold rolling is such that the crack initiation is difficult because of quicker passivation characteristics of the crack initiating plane. The texture also gives unfavourable orientation of slip and twinning planes with respect to tensile axis. The crack initiating planes are identified with the help of X?ray pole figures. The apparent activation energy is found to be texture dependent at a given stress level. On the basis of apparent activation energy measurements, dynamic tests at constant cross?head speeds and electrochemical measurements, the mechanism of SCC is identified to be the one involving stress?aided anodic dissolution. Copyright 1982 Verlag GmbH & Co. KGaA, Weinheim