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Porous Cu–Al–Ni shape memory alloys (SMAs) are fabricated via powder metallurgy method using Cu, Al, Ni powders and Cu–Al–Ni alloy powder as raw materials, respectively. It is found that the two kinds of specimens have similar macroscopic morphologies: connected pores are uniformly distributed in the Cu–Al–Ni matrix, forming a 3D network structure. By comparison, the specimen fabricated using alloy powder has much finer microstructures than the specimens fabricated using Cu, Al, Ni powders. After adding Ce element to the latter, the microstructure of the Cu–Al–Ni matrix is significantly refined because of the formation of Ce‐rich particles. Damping tests show that the latter has superior damping capacity than the former. With the increase of Ce content, the damping of the latter increases first and then decreases. When the Ce content reaches 0.05 wt%, the highest damping can be achieved. Correlated mechanisms are discussed based on the microstructural observations. [ABSTRACT FROM AUTHOR]

High speed steel T15 particle reinforced copper matrix composites were prepared using powder metallurgy. A systematic investigation was conducted into the effects on the microstructure and mechanical properties of the composites of the sintering temperature, T15 hard particle content, and particle size. The results indicate that the grain size is efficiently refined by the addition of T15 hard particles. The decrease in grain size of 10 wt% T15/Cu composite is from 6.87 μm to 1.34 μm at the same sintering temperature, and the grain size is proportional to both the sintering temperature and the size of hard particles. As the sintering temperature increases, the relative density and hardness of the composite gradually increase, while the yield strength initially increases and then declines. When sintered at 790 °C, the 10 wt% T15/Cu composite achieved a maximum yield strength of 160.1 MPa, which is 178.9 % and 30.6 % higher than that of pure copper and 10 wt% TiC/Cu composites, respectively. There are no visible cracks after compression, and a good balance of strength and toughness is achieved. Meanwhile, the primary contributions of strengthening mechanisms such as grain refinement, thermal expansion mismatch and load transfer to the mechanical properties of T15/Cu composites were analyzed. It is anticipated that this will establish a foundation for the preparation and application of high-performance copper matrix composites reinforced with metal particles. • High speed steel T15 particle reinforced copper matrix composites were prepared using powder metallurgy. • The addition of T15 hard particles can effectively refine the grain size. • The mechanical properties of the T15/Cu composites showed a significant improvement. • The strengthening mechanism of T15/Cu composites was quantitively analyzed. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the temperature spectra of internal friction and relative dynamic modulus of a Cu–11.9Al–2.5Mn (wt.%) alloy. It is found that a peak appears at around 350 °C during the first heating process of the quenched specimen. The peak occurs not only during heating but also during cooling. Its activation energy has been calculated to be 1.85±0.17 eV in terms of the Arrhenius relation. In addition, the peak disappears in specimens during the second or more heating process, because an overlap occurs between the peak and the reverse martensitic phase transition peak. During cooling, however, the peak can be seen all the time. It is suggested that the peak originates from Zener relaxation. [Copyright &y& Elsevier]