A New Lead-Free Copper Alloy CuAl8Fe5Ni4Zn4Sn1 for Plain Bearings and Its Strengthening Mechanisms

Abstract

CuAl8Fe5Ni4Zn4Sn1 (OF 2238) is a new lead-free copper alloy for plain-bearing applications that was first officially presented in a scientific journal in 2020. Soon after its invention, the use of the alloy for connecting rod bushings in heavy-duty internal combustion engines was promoted and validated with customers. The aim of this article is to describe the material properties of the new alloy in more detail than previously and explain how the advantageous properties of CuAl8Fe5Ni4Zn4Sn1 are generated. At the beginning of this article, the general development trends in the field of copper alloys for sliding applications are presented, into which the new alloy from this publication can be classified. In the main part of this publication, the authors go through the production chain of CuAl8Fe5Ni4Zn4Sn and show how the entire manufacturing process contributes to obtaining a material with a combination of high strength, ductility and sufficient toughness. This starts with fine microstructures after casting, followed by homogenisation and refinement during hot extrusion and work hardening chiefly during cold drawing. What is most surprising, however, is the finding that a strong hardening effect can be achieved in the new alloy by precipitation of fine κ-phase at temperatures of about 400 °C and air cooling without prior solution treatment. These results make it clear that there is great potential for further material developments to support material efficiency and even to expand the application limits.