Xiuqing Li

In this work, Mo particles were incorporated into a Cu matrix, with the hope of retaining the advantageous properties of Cu while improving its mechanical performance. Mechanical ball milling was employed to fabricate Cu-Mo composite powders with different Mo concentrations; the Mo particles were incorporated at mass fractions of 5%, 10%, 15%, and 20%, which were subsequently densified by spark plasma sintering (SPS) to achieve a high-density composite. Phase identification and microstructural analysis were performed using X-ray diffraction (XRD). Tensile strength, compressive strength, and Vickers hardness measurements were performed to evaluate the mechanical performance of the Cu-Mo composite. Microstructural characterization of the tensile specimen was conducted via electron backscatter diffraction (EBSD), energy dispersive X-ray spectroscopy (EDS), and field-emission scanning electron microscopy (FE-SEM). The results demonstrate a consistent decrease in grain size and a corresponding increase in density with higher Mo content in the composite. For Cu-15wt%Mo composite, the Vickers hardness is 135 HV, compressive strength is 300 MPa, and tensile strength is 371 MPa. Compared with pure Cu, they were increased by 74%, 115%, and 64%, respectively. The main strengthening mechanisms have been revealed. This research can offer a foundation and reference for designing and developing high-performance Cu-Mo composite.

The effect of sliding velocity on the tribological performance of a B ₄ C‐hBN/TC4 titanium alloy tribo‐pair is systematically investigated in artificial seawater. Worn surfaces and the chemical composition of the tribofilm are characterized by scanning electron microscopy, 3D profilometry, energy‐dispersive X‐ray spectroscopy, Raman, and X‐ray photoelectron spectroscopy. Results show that a 30 wt% hBN content yields the lowest coefficient of friction (COF) and wear rate. As the rotational speed increases from 510 to 750 r min ⁻¹ , the lubrication regime transitions from boundary to mixed, leading to a steadily decreasing COF. This phenomenon is directly linked to the formation and stabilization of a protective tribofilm. The film, rich in low‐shear‐strength compounds such as Ca(OH) ₂ , Mg(OH) ₂ , CaCO ₃ , and H ₃ BO ₃ , effectively lubricates and protects the contact surfaces. However, further increasing the speed to 1 000 r min ⁻¹ generates excessive frictional heat at the contact interface. This thermal effect degrades the protective tribofilm by reducing its viscosity and thickness, ultimately compromising its integrity. As a result, the lubrication regime fails, leading to a deterioration in tribological performance, as evidenced by a sharp increase in the COF.