Ni-Mn-Ga alloys exhibit supelastic and magnetic shape memory effect as discussed

Question

Ni-Mn-Ga alloys exhibit supelastic and magnetic shape memory effect as discussed in class. Two other important properties of these alloys are the magnetocaloric effect and a negative magnetoresistivity. A) What is the magnetocaloric effect and negative magnetoresistivity? What is their practical significance? B) How are these effects being used in commercial applications? (you can use any reference on science direct or other data bases to answer this part. Cite your refernces clearly.) C) The mechanical behavior of these alloys is shown below. Estimate the modulus and tensile strength for 0%Dy and compare it to NiTi. D) The addition of the rare earth element Dy to these alloys is important in improving the mechanical properties. Plot the variation of approximate strength and ductility as a function of Dy content. What would be the optimum Dy content? E) Note also the Curie temperature (Tc) data for various Dy additions. What is the significance of this variation of Curie temperature?

TC (K)       352         349         351         350         305

%Dy        0               0.25        0.50        1.0           2.0

Explanation / Answer

Magentocaloric effect is an thermodynamic property in simple words change in form with respect to temperature as the temperature changes due the presence of any magnetic field the the conductivity of the magnet changes .Negative magnetorestvity means the decrease in conductivity to act like magnet in the presence of increased magnetic filed these properties studied on few dilute alloys .

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