Crack Initiation and Small Crack Growth Behavior of Age-Hardened Cu-6Ni-2Mn-2Sn-2Al Alloys
Masahiro GOTO, Seung-Zeon HAN, Chang-Joo KIM, Takaei YAMAMOTO and Norio KAWAGOISHI
Abstract:In order to clarify the fatigue behavior of Cu-6Ni-2Mn-2Sn-2Al alloy which was aged (400, 3h) after 80% swaging, fatigue tests of smooth specimens have been carried out. In addition to this, fatigue tests of the alloy with 0.1% Zr have been performed. The plastic replication technique was used for monitoring the crack initiation and propagation behavior. Experimental results showed that the crack initiation life of Zr added alloy is larger than no Zr alloy. The crack initiation sites of the alloys were both the grain boundary and slip bands independent of Zr addition. With regard to a major crack which led to the final fracture of the specimen, however, the initiation sites for Zr added alloy tended to be in the slip bands. For no Zr added alloy, the major cracks tended to initiate from the grain boundary. Thus, it can be concluded that the crack initiation resistance at the grain boundary increases due to the Zr addition. This increased resistance for crack initiation may result from the Zr particles precipitated at the grain boundary by the heating of ageing. On the other hand, a slight effect of Zr addition on crack growth behavior was observed. Key Words:Fatigue, Cu-6Ni-2Mn-2Sn-2Al alloy, Ageing, Crack initiation, Crack propagation, Zr addition, Precipitation strengthening