The effects of tetravalent transition metals on Cu-Al based shape memory alloy

In this thesis, the effect of two different transition metals (Zirconium and Hafnium) additive on some physical properties (thermal, electrical, magnetization, and mechanical) of Cu-Al-Mn shape memory alloy has been studied. The samples were manufactured by using the arc melting method in a controlled environment in four different compositions includes CAM (Cu_70 Al_24 Mn_6 at%), CAMZ (Cu_69 Al_24 Mn_6 Zr_1 at%), CAMH (Cu_69 Al_24 Mn_6 Hf_1 at%), and CAMZH (Cu_69 Al_24 Mn_6 Zr_0.5 Hf_0.5 at%). The DSC results showed that the adding of tetravalent transition metals (Zirconium and Hafnium) caused to decrease in the austenite phase transformation temperatures, but the martensite phase transformation temperatures were increased after adding Zr and Hf. And the temperature hysteresis was decreased. Also, the same result was obtained in the measurement of electrical resistivity. According to XRD analysis, all samples have the same pattern which has martensite phase in two different morphologies (β_(1 )^' 〖and γ〗_1^'), and the SEM analysis showed the same result. Besides, both Zr and Hf were caused to reduce the crystallite size of Cu-Al-Mn alloys. The magnetization measurement investigated that Cu-Al-Mn alloy has the ferromagnetic property at room temperature but alloying of Zr and Hf caused to change its magnetic property from ferromagnetic to paramagnetic.