In this study, an innovative internal oxidation-powder metallurgy combined process was employed to controllably generate nano-sized Cr₂O₃ reinforcing phases within the Cu matrix. The Cu/Cr₂O₃ composites were successfully fabricated using the hot-press sintering (HP) method, and a systematic comparison was made between the microstructure and mechanical properties of composites prepared by internal oxidation and external addition methods. The results show that internal oxidation primarily occurs during the sintering process rather than ball milling. Compared with external addition, the internal oxidation method effectively prevents particle aggregation and achieves a uniform distribution of Cr₂O₃ particles in the Cu matrix. When the Cr content reaches 5 wt%, the Cu-5%Cr composite exhibits optimal mechanical properties, with a yield strength of 282.7 MPa and ultimate tensile strength of 355 MPa, representing increases of 43% and 34% over pure copper, respectively, while maintaining an elongation of 12.6%. The Cr₂O₃ particles generated via internal oxidation enhance their strength through Orowan strengthening and dislocation pinning, thereby significantly improving mechanical performance without compromising plasticity. This research provides a novel process optimization approach for developing high-performance dispersion-strengthened copper matrix composites.

Au-17.5Ni is a high-performance solder extensively utilized in the assembly of satellites, aircraft engines, and ceramic components, owing to its exceptional high-temperature properties. However, its inherent brittleness renders it susceptible to defects such as fractures, cracking, and delamination during the manufacturing of welding wires and foils. To mitigate these challenges, this study employs first-principles calculations to investigate the structural stability, mechanical properties, and thermal behavior of the primary phase in the Au-17.5Ni alloy, with a particular focus on the Au-rich phase, a solid solution of Ni in Au. The results indicate that the Au-2.0Ni composition exhibits the highest plasticity, characterized by a Pugh’s ratio (B/G) of 7.671 and a hardness value of 0.643 GPa, representing a 31.76% increase compared to pure Au. These improvements significantly enhance the processing performance of the Au-17.5Ni alloy. Moreover, the constant pressure specific heat capacity (C_p) of Au-xNi alloys exceeds that of pure Au and increases with higher Ni content. At 800 K, the Au-3.0Ni alloy exhibits the highest C_p at 31.179 J mol⁻¹·K⁻¹, indicating improved high-temperature stability. Additionally, the thermal expansion coefficients for Au-1.0Ni, Au-2.0Ni, and Au-3.0Ni increase by 13.037%, 22.858%, and 38.097%, respectively, which may lead to elevated thermal stresses in welded joints. Consequently, maintaining the Ni content in the Au-rich phase of the Au-17.5Ni solder below 2.0 wt% can significantly enhance solder processability, ultimately improving the yield of welding wires and foils.