Martensitic Transformation, Mechanical Properties and Corrosion Resistance of Ni48Co1Mn37In14- x Al x Magnetic Shape Memory Alloys

Abstract:

The effect of Al doping on microstructure, crystal structure, martensitic transformation, mechanical properties and corrosion resistance of Ni₄₈Co₁Mn₃₇In_14-xAl_x (0≤x≤2) magnetic shape memory alloys was studied by the material preparation method of arc melting. The results show that the grain size of the alloy is reduced by replacing part of In with Al, and the average grain size is reduced to about 10 μm when 2at% Al element is doped, which is about 1/35 of that of the undoped sample. When the doping amount of Al is 0.25at%?2at%, the metal Al is completely dissolved into the matrix, and the solid solubility of Al in the alloy increases with the increase in the doping amount; when the doping amount is 2at%, the solid solubility of Al in the matrix is close to 2at%. With the substitution of Al for In, the alloy changes from the two-phase structure of L2₁ cubic austenite and monoclinic 6M martensite to a single 6M at room temperature, the unit cell volume gradually decreases, and the martensitic transformation temperature shows an upward trend. The compressive strength of the alloy continues to increase, and compared with that of Ni₄₈Co₁Mn₃₇In₁₄, the compressive fracture strength of Ni₄₈Co₁Mn₃₇In₁₂Al₂ is increased by 160%, and the compressive strain also increases from 5.46% to 6.36%. After an appropriate amount of Al replacing In, the corrosion resistance of the alloy in artificial seawater generally shows an increasing trend. The corrosion resistance of Ni₄₈Co₁Mn₃₇In₁₂Al₂ alloy is significantly higher than that of Ni₄₈Co₁Mn₃₇In₁₄ alloy, and its corrosion resistance is close to that of 304 stainless steel.

Key words:magnetic shape memory alloy;metal Al doping;martensitic transformation;mechanical properties;corrosion resistance