Effect of Mn/P Atomic Ratio on the Microstructure and Properties of Cu-Mn-P Alloy

Abstract

In this study, Cu-Mn-P alloys with Mn/P atomic ratios ranging from 1 to 3 were designed based on computational phase diagrams. The microstructures of these alloys were systematically investigated using a combination of TEM, EPMA, EBSD, and XRD. The results indicate that the alloy with a Mn/P atomic ratio of 2 exhibits optimal comprehensive properties. A simple thermomechanical treatment involving solution treatment followed by 70% cold rolling and aging at 400°C for 6 hours resulted in a hardness of 186.8 HV, a tensile strength of 577 MPa, a yield strength of 548 MPa, and an electrical conductivity of 63.5% IACS. Alloys with Mn/P ratios below 2 showed a reduced density of precipitates, leading to diminished precipitation hardening, while higher ratios resulted in increased manganese content in the solid solution, causing lattice distortions and reduced conductivity. TEM analysis confirmed that the precipitated phase was rod-shaped hexagonal Mn₂P, which grew along the (100) plane of the matrix and maintained a coherent interface with the matrix. This research provides insights for the future development of high-performance quaternary Cu-Mn-X-P alloys.