Effect of Zr addition on the fatigue strength of Cu-6Ni-2Mn-2Sn-2Al alloy

Abstract

Fatigue tests of Cu-6Ni-2Mn-2Sn-2Al alloy smooth specimens were carried out to clarify the effect of trace Zr on the fatigue strength. The growth behaviour of a major crack, which led to the final fracture of the specimen, was monitored to study the physical basis of fatigue damage. When stress amplitude was less than σ a = 350 MPa, the fatigue life of Zr-containing alloys was about two times larger than that of alloys without Zr. When σ a > 350 MPa, increments of fatigue life due to Zr decrease with an increase in σ a and the increments were negligible at σ a = 400 MPa. Increased fatigue life due to Zr addition resulted from an increase in crack initiation life and microcrack growth life. The growth rate of a small crack was determined by a term, σ a n l, independent of Zr addition. The effects of trace Zr on fatigue strength were discussed with relation to the initiation and propagation behaviour of a major crack.