Stress Corrosion Crack Propagation Behaviour of Ultra-Fine Grained Copper Produced by Equal-Channel Angular Pressing Technique
Takashi YAMASAKI Hiroyuki MIYAMOTO and Takuro MIMAKI
Abstract:Stress corrosion crack (SCC) propagation tests have been carried out in 1 kmol/m3 sodium nitrite aqueous solution to investigate SCC propagation behaviour of ultra-fine grained (UFG) copper produced by equal-channel angular pressing (ECAP) technique. SCC propagation tests have been performed on Compact Tension (CT) specimens under constant load. Phenomenon of SCC propagation was estimated from the crack propagation rate (da/dt) and the stress intensity factor (KI). Relationship between the da/dt and the KI in UFG copper could be divided into region I and II. The da/dt increased with the KI in region I. The da/dt was independent of the KI and showed constant value in region II. SCC in UFG copper had propagated along grain boundary. On the other hand, the transgranular SCC propagation was observed in polycrystalline copper. The anodic dissolution mechanism should be considered for the SCC of UFG and polycrystalline coppers. The SCC propagation in UFG copper could be understood from the film rupture and dissolution if the grain boundary sliding is considered as a dominant slip event. Key Words:Ultra-fine grained copper, Equal-channel angular pressing technique, Stress corrosion crack, 1 kmol/m3 sodium nitrite aqueous solution, Intergranular crack, Grain boundary sliding