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This study investigates the damping properties of Cu–Al–Mn shape memory alloys (SMAs) with various chemical compositions and the effects of the addition of quaternary alloying elements Ag and Nb on the microstructure, martensitic transformation behavior, and damping capacity of SMAs. Compared to other Cu–12Al– x Mn (x = 4–7 wt%) SMAs, Cu–12Al–5Mn has a more significant inherent and intrinsic internal friction (IF PT + IF I) peak above room temperature. The addition of Ag or Nb to Cu–12Al–5Mn reduced the grain size, thereby increasing the hardness of the alloys; however, the damping capacity and temperature of the IF PT + IF I peak decreased simultaneously. The addition of Ag to Cu–12Al–5Mn significantly reduced the damping capacity (IF PT +IF I peak) because of the notable decrease in the amount of transformed martensite. Moreover, the addition of Nb to Cu–12Al–5Mn caused the AlNb 3 phase to precipitate, limiting the mobility of the martensite variant interfaces and slightly decreasing the damping capacity (IF PT + IF I peak). Among the Ag- and Nb-doped Cu–12Al–5Mn SMAs, Cu–12Al–5Mn–1 Nb showed not only a significantly higher hardness but also a higher IF PT + IF I peak, with tan δ exceeding 0.01 at approximately 50 °C. [Display omitted] • In Cu-based SMAs, damping capacity depends on microstructure and the volume fraction of the transformed martensite. • Alloying elements with different mechanisms affect the damping performance of Cu-based SMAs. • In Cu-based SMAs, both damping capacity and mechanical strength improve by optimizing chemical composition. [ABSTRACT FROM AUTHOR]

Abstract: The phase equilibria in the Co–W–V ternary system were experimentally investigated by optical microscopy (OM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) on the equilibrated alloys. Three isothermal sections of the Co–W–V ternary system at 1100°C, 1200°C and 1300°C were determined, and no ternary compound was found in this system. In addition, a novel phenomena induced by the liquid phase separation in the Co–W–V alloys was firstly discovered, suggesting that a stable liquid miscibility gap exists in the Co–W–V ternary system. The newly determined phase equilibria and firstly discovered phase separation phenomena in the Co–W–V system will provide important information for the development of Co–W based alloys. [Copyright &y& Elsevier]

The influence of Gd element and solution treatment on the microstructure of AZ31 alloy was investigated in this paper. The microstructure and phase composition were characterized by OM, SEM, EDS and XRD. The results indicate that Mg 17 Al 12 eutectic phase, scattered along the grain boundary, is suppressed effectively with Gd addition and the acicular Al 2 Gd superlattice with lamellar distribution is formed. Furthermore, the grain size of AZ31 alloy is also refined with Gd addition. In the subsequent process of solution, the migration and growth of Al 2 Gd phase conforms to Ostwald Ripening Theory. The morphology of Al 2 Gd phase becomes granular and scatterd in matrix uniformly after solution for 16 h at 813 K. [ABSTRACT FROM AUTHOR]