Cu-xNi-5Sn (wt %) alloys with a different Ni content were prepared by a powder metallurgy method. The effect of Ni content on the hardness and yield strength of Cu-xNi-5Sn (wt %) alloys was investigated. The microstructure, composition, and morphology of Cu-xNi-5Sn (wt %) alloys were observed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and cold field emission scanning electron microscope (FESEM), respectively. Results indicate that the hardness and yield strength firstly increase and then decrease with the increase of Ni content and reach up to a maximum when Ni content is 12.5 wt %. Furthermore, the formation of the sandwich structure and needle-like phase is found in the grain, the grain boundary and intragranular precipitates are rich in both the Ni and Sn phase. The formation of the inerratic and suitable lamellar precipitates of sandwich structure and needle-like phase can be responsible for the good mechanical properties of the Cu-12.5Ni-5Sn alloy after aging treatment. The sandwich structure and need-like phase that were observed by FESEM can contribute to clarify the morphology of Cu-Ni-Sn alloys.

Friction tests were conducted on self-matched pairs of medium-carbon steel using a pin-disk tribometer in an ambient laboratory environment with and without wear-debris removal, in order to clarify the influence of wear debris on the tribological properties of steels that were exposed to magnetic fields. The wear debris and worn surface were observed and analyzed. In the case that the wear debris was removed, the vast majority of wear debris was large, scarce oxidation, and no agglomeration, the grooves of various shapes and discontinuities, and no oxide layer were formed on the worn surface, severe wear occurred throughout the friction process. When the wear debris was not removed, the wear debris became fine, agglomeration and oxidation, a debris layer was formed on the worn surface, and the wear mode transitioned from severe to mild occurred during friction process. The results reveal that the re-entering of wear debris into the friction area is essential for the formation of a wear-debris layer and that an anti-wear effect can be achieved via the wear-debris layer formed on the worn surface during the friction process with a magnetic field.

In response to the need to optimize the performance of copper–graphite current-carrying friction materials, spark plasma sintering (SPS) technology was used to prepare copper–graphite composite materials with different graphite orientations. A self-made current-carrying friction testing machine was used to study the effect of graphite orientation on the current-carrying friction performance of copper–graphite composites. The results showed that as the graphite orientation increased, the current-carrying friction performance of the copper–graphite composites initially improved and then deteriorated. The performance was optimal when the graphite orientation of the 7.5 wt% graphite–copper composite was 90°, primarily constrained by the wear rate. The main wear mechanism was furrowing, and graphite enrichment occurred on the worn surface, where the graphite content on the wear surface was higher than that in the bulk material. The degree of enrichment varied under different wear mechanisms. The graphite content near the entry region of the friction surface was significantly lower than that near the exit region.