Influence of deformation and
heat treatment of polycrystalline Ni2.19Fe0.04Mn0.77Ga
alloy on the microstructure
evolution and development of the martensitic transformation
I. Musabirov1, I.
M. Safarov1, I.
Z. Sharipov1, R.
V. Mashirov2, V.
for Metals Superplasticity Problems of Russian Academy of Sciences, Ufa,
Kotelnikov Institute of Radio-engineering and Electronics of RAS,
The paper is received on January 11, 2015
The results of a study of the physical properties of polycrystalline Ni2.19Fe0.04Mn0.77Ga
alloy in initial cast state, after severe plastic deformation by torsion under
pressure and after annealing of deformed material at temperatures of 400°C,
500°C, 600°C and 700°C are present. Record the temperature dependence of the
magnetization and electrical resistivity in the initial cast alloy shows that
the temperature intervals of the martensitic and magnetic transitions overlap.
According to the study of the microstructure of the alloy in different
structural states, the dependence of the average grain size of the
recrystallized structure in the sample from the degree of annealing is
established. It is shown that the martensitic structure of the material is
observed only after annealing of the deformed alloy at 500°C. As a result of
severe plastic deformation of the investigated alloy the ferromagnetic ordering
is destroyed and the martensitic transformation is suppressed. Subsequent heat
treatment of deformed alloy leads to a gradual recovery of ferromagnetic order.
Key words: shape
memory effect, ferromagnetic shape memory effect, martensitic transformation, severe
plastic deformation, NiMnGa alloys.