EFFECT OF MICROSTRUCTURAL MODIFICATION ON TENSILE AND FATIGUE PROPERTIES OF CU-35WT-PERCENT NI-3.5WT-PERCENT CR ALLOY

Tensile and fatigue properties of Cu-35wt%Ni-3.5wt%Cr in four different material conditions have been investigated. It is shown that reduced grain size and enhanced dislocation density lead to an increase in tensile as well as fatigue strength of solution treated specimens. In the presence of precipitates, tensile properties are less dependent on grain size. Similar to tensile strength, LCF strength is improved by precipitation hardening. However, for large-grained material, the effect of precipitation hardening in the HCF region is reduced due to pronounced intergranular cracking. On the other hand, the intergranular cracking can be reduced by grain refinement, so that an improvement of HCF properties is then possible while taking advantage of precipitation hardening. Results obtained by TEM-investigation of deformed specimens are also discussed in connection with deformation behaviours of the material conditions.