Search

This paper completes the welding of 4-mm-pure copper with bobbin tool-friction stir welding technology for the first time, and we discovered the evolution of microstructure by combining the temperature field evolution, microstructure, mechanical properties, electrical properties, and chemical corrosion resistance of welded joints. The findings demonstrate that the temperature field is dynamic, with the advancing side experiencing the highest peak temperature (422 °C). The size of recrystallized grain in the stir zone (SZ) is slightly larger than that of the base metal (BM), and the "banded structure" of alternating coarse-grain bands and fine grain bands is observed in this region. The microstructure of the heat-affected zone (HAZ) has larger grain size. Both the advancing and retreating sides of the thermomechanically affected zone (TMAZ) have a distinct microstructure, with the advancing side having a more pronounced elongated and curved microstructure. The welded joint has a specific microstructure gradient from the standpoint of the overall microstructure, which results in the fracture location at TMAZ with the biggest microstructure gradient in the tensile test, and the welded joint's efficiency is only 57.56% of the base metal. At the same time, the resistivity and the chemical corrosion resistance of the welded joint will decrease. During the welding process, the grains in the stir zone mainly undergo geometric dynamic recrystallization and the heat-affected zone mainly undergoes dynamic recovery. [ABSTRACT FROM AUTHOR]

Although copper has excellent thermal conductivity, poor wear resistance seriously limits its development. In this paper, a Cu matrix surface composite material reinforced by FeCoNiCrAl high-entropy alloy particles was prepared by friction stir processing. The microstructure and properties of the composite were investigated. The results showed that both the FSP process and the addition of HEA particles contributed to the refinement of the Cu-matrix grains. A diffusion layer with a width of about 0.8 µm was formed at the interface between the HEA particles and the Cu matrix. Compared with received Cu, the microhardness of Cu matrix in the composites was increased by 69.8%, the wear rate was reduced by 29.7%, and the wear resistance was significantly improved. Mean while, the ductility of the composite was consistent with that of the received Cu, and the thermal conductivity reached 87% of the received Cu. Therefore, this paper provided a new possibility for developing multifunctional structural materials with high wear resistance, high ductility, and high thermal conductivity. • HEA particle reinforced Cu-matrix surface composites were successfully prepared via FSP, and the grain size of the matrix was significantly reduced. • HEA particles and Cu matrix formed a diffusion layer continuous with good interfacial bonding. • Compared with traditional particle reinforcement, HEA particle was an excellent reinforcement particle. • The prepared surface composite has significantly improved wear resistance, while maintaining good ductility and thermal conductivity. [ABSTRACT FROM AUTHOR]

The effects of adding a small amount of the rare earth (RE) element Gd into a high-strength Mg97Zn1Y2 alloy containing a long periodic stacking ordered (LPSO) phase on the microstructure, phase composition, and corrosion behavior of the alloy were investigated. By adding different contents of X wt% Gd (X=0,3,6,10). With the incorporation of the rare earth element Gd, the morphology of the secondary phase underwent a continuous transition from a continuous network-like form to a discontinuous and blocky phase. The electrochemical test results show that the corrosion current density of Mg97Zn1Y2 is 13.62 μA/cm2 higher than that of the Mg97Zn1Y2–10 wt%Gd alloy. At this time, Mg97Zn1Y2–10 wt%Gd alloy exhibits the best corrosion resistance, which has improved by 2.11 % compared to the substrate. Additionally, the number of pitting pits and corrosion products formed on the surface of Mg97Zn1Y2–10 wt%Gd alloy is lower than that of other alloys. • Adding Gadolinium to Mg97Zn1Y2 alloy affects the dispersion of the second phase, the structural shape, and the content change. • The emergence of the Mg12Zn (Y, Gd) composite phase enhances the nucleation and growth rates of the LPSO phase. • Corrosion resistance is enhanced when the second phase is uniformly distributed and structurally continuous in the alloy. [ABSTRACT FROM AUTHOR]