Study Of Microstructure And Properties Of CuZnAl(Dy,Gd) Shape Memory Alloys

The microstructure, phase transformation behavior, shape memory effect and anti-corrosion behavior of CuZnAl(Gd,Dy) shape memory alloys are investigated by optical microscope, scanning electronic microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC), bending method and electrochemical measurement. The effect of rare earth Dy and Gd on the microstructure and properties of CuZnAl alloys is investigted.The results show that thin spherical phases, which are rare earth rich phase, precipitate in the matrix of CuZnAl alloy. The cast microstructure of CuZnAl alloy is refined efficiently by the spherical phases and the growth of the grains during the solid treatment is also stunted. With 0.08wt.% rate earth addition, the grains is diminished from 0.52mm to 0.3mm, and the fracture behavior is changed from brittle to ductile fracture. Rare earth addition can increase the martensitic transformation temperatures of CuZnAl alloys and improve the stability of the alloy under aging or thermal cycling process. With the increase of the content of rare earth element, the shape recovery ratio increases and reaches its maximum value with 0.08wt.%Dy or 0.08-0.12wt.%Gd addition, respectively. Uniform corrosion occurs of CuZnAl alloy which is immersed in NaCl and NaOH solution, and the anticorrosion property is improved. In electrochemical measurement, rare earth Dy or Gd addition decreases the OCP value of CuZnAl alloy in 3.5% NaCl solution and the corrosion current density.