Effect of the Mn Additive on Cu-Zn-Al Shape Memory Alloy
Chemical and Materials Engineering
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This thesis has reviewed the development and the current status in the research field of copper-based shape memory alloys including the Cu-Al-Ni, Cu-Zn-Al, Cu-Al-Mn, Cu-Al-Be, and other copper-based shape memory alloy. From the standpoint of mechanisms (phase transformation, thermodynamics) and properties (shape memory effect, mechanical properties), this thesis summarizes the previous research and contributions to improve the properties of copper-based shape memory alloys.A polycrystalline Cu-Zn-Al shape memory alloy was developed and studied. The grain refinement, eutectic structure, and the precipitates were investigated. The microstructure of the alloy has been observed and analyzed; grains are significantly refined by the addition of manganese. The lamellar structure of the alloy has also been discussed. The shape memory effects were evaluated with bending tests, and the results indicate that for the sample without any addition of Mn, the shape recovery is 7 ̊, and for the alloy with 1 % Mn, 5 ̊. The shape memory effect of the newly developed alloy was not significantly decreased although the grains were dramatically refined. The phase transformation procedure and the solidification process were explored; the heat treatment was discussed, and the oxidation and diffusion of the alloy were scrutinized.