Atom probe tomography characterisation of powder forged connecting rods alloyed with vanadium and copper

Abstract

The precipitation of V and Cu in the powder forged connecting rods of Fe-V-Cu-C alloy, were studied by atom probe tomography (APT). The purpose of alloying with V was to further improve the mechanical properties of the existing powder forged materials based on Fe-Cu-C. In this study, materials tested at room temperature and 120°C were investigated. It was found that Cu was unevenly distributed on a micrometer scale. The local Cu content affected the Cu precipitation; a higher Cu content resulted in a higher volume fraction of precipitates. The V was found to form very small nitrides. The N presumably originates from the sintering process. The vanadium nitrides act as nucleation points for the Cu precipitates during cooling of the material during fabrication. APT analysis of the deformed material close to the fracture surface of the tensile test samples showed a similar volume fraction of Cu precipitates, but statistical analysis of the data indicates that both Cu and VN precipitates are more diffuse than in the undeformed material.