Surface Alloying on Cu with Mo by High-Current Pulsed Electron Beam Irradiation

Molybdenum (Mo) and copper (Cu) belong to the binary mutually insoluble system. However, Copper-molybdenum (Cu-Mo) composite materials, which combine the high-temperature hardness and strength of Mo with the excellent conductivity and thermal conductivity of Cu, have important applications in electric contacts, heat dissipation components, and other fields. The problem is that the solid solubility between Cu-Mo is extremely low, making it difficult to achieve alloying, which greatly limits the excellent performance of Cu-Mo composite materials. In this study, high current pulsed electron beam (HCPEB) irradiation technology was used to realize the surface alloying of the Cu-Mo immiscible system to improve the properties of materials. HCPEB was used to irradiate the Cu matrix of Mo coating powder prepared, and the effects of different pulse times on the solid solubility, phase structure, and surface hardness of the sample were studied. The results show that HCPEB irradiation can effectively improve the solid solubility of the Cu-Mo mutually insoluble system. The maximum level of solid solubility of Mo in the Cu lattices is reached after 15-pulsed irradiation. The microstructure image shows that a large number of spherical and molar Mo particles can be observed in the surface layer of the sample after 15 HCPEB irradiation. When the number of irradiation increases to 35 times, Cu(Mo) solid solubility decreases due to the thermal decomposition of Cu(Mo) solid solution. Microstructural characterization shows that a large number of spherical and molar Mo particles can be observed in the surface layer of the irradiated sample after HCPEB irradiation. After multiple pulse irradiations, most of the Mo particles tend to be distributed at crystal defects. There is a certain orientation relationship between the precipitated Mo particles and the Cu matrix. The performance test results show that the surface hardness of the HCPEB irradiated sample with Mo increases significantly with the increase of pulse numbers. The performance test results show that the hardness of the Cu(Mo) alloying surface layer significantly increases with the increase of irradiation times after HCPEB alloying treatment. This is not only the result of solid solution strengthening, but also the dislocation strengthening and dispersion strengthening of small Mo phases in the Cu(Mo) alloying surface layer jointly improve the properties of the alloying surface layer.