Mechanical behaviour and damping properties of Ni modified Cu-Zn-Al shape memory alloys

The microstructure, mechanical behaviour and damping properties of Cu-18Zn-7Al-xNi alloys (where x = 0.1, 0.2, 0.3 and 0.4) were investigated. The Cu-Zn-Al alloys were produced by casting and then subjected to a homogenization - cold rolling - annealing treatment scheme. Optical-, scanning electron-microscopy and X-ray diffraction analysis were utilized for structural characterization of the alloys, while tensile test, fracture toughness, and hardness measurement were used to assess the mechanical properties. The results show that all the alloy compositions consisted of the predominating CuZn phase. Sharp edged elongated grain structures were observed in the unmodified and the 0.4% Ni modified CuZnAl alloys, while the 0.1, 0.2 and 0.3 %Ni modified CuZnAl alloy compositions, had more of granular/curved/round grain edges and smaller grain widths. The hardness of the unmodified CuZnAl alloy (294.5 ± 2.08 VHN) was lower than that of the Ni modified CuZnAl ones with an increase in hardness ranging between 23.5 and 38.4%. The tensile strength, the percentage elongation (10.7-14.3%) and the fracture toughness of the 0.1, 0.2 and 0.3% Ni modified CuZnAl alloys were observed to be higher than those of the unmodified and the 0.4 %Ni modified CuZnAl alloys. The 0.2% Ni modified CuZnAl alloy had the highest damping capacity among all compositions under investigation, while the 0.4% Ni modified one showed the least capacity to serve as a damping material.