Presentation Title

Martensitic phase transition in NiTi thin-film alloys

Advisor Information

Renat Sabirianov

Location

UNO Criss Library, Room 112

Presentation Type

Oral Presentation

Start Date

7-3-2014 3:15 PM

End Date

7-3-2014 3:30 PM

Abstract

In the present work, we examine the martensitic phase transition of the shape memory alloy (SMA) NiTi. We are interested in whether a homogeneous external magnetic field can be used to affect the phase transition during heating and cooling. This theoretical simulation utilizes a Monte Carlo method written in Python to simulate the interatomic interactions during cooling and heating of the NiTi lattice. Starting from a cubic structure at 300K, the program simulates cooling to 240K and we observe that the phase transition occurs at approximately 250K – 260K. Upon cooling, the NiTi lattice transitions from a cubic to a rhombohedral structure regardless of the presence of the external magnetic field. However, upon heating the sample back to 300K, we see two cases. In the first case, the lattice transitions from rhombohedral to a cubic structure in the presence of the external magnetic field. For the second case, the lattice transitions from rhombohedral to a monoclinic structure without the external magnetic field. We also found that when subjected to this external magnetic field, the phase transition during cooling is not as abrupt, i.e. an external magnetic field softens the typically first order phase transition. Our study suggests that magnetic fields can indeed be used to affect the phase transition of NiTi and this idea may extend to other SMAs as well.

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Mar 7th, 3:15 PM Mar 7th, 3:30 PM

Martensitic phase transition in NiTi thin-film alloys

UNO Criss Library, Room 112

In the present work, we examine the martensitic phase transition of the shape memory alloy (SMA) NiTi. We are interested in whether a homogeneous external magnetic field can be used to affect the phase transition during heating and cooling. This theoretical simulation utilizes a Monte Carlo method written in Python to simulate the interatomic interactions during cooling and heating of the NiTi lattice. Starting from a cubic structure at 300K, the program simulates cooling to 240K and we observe that the phase transition occurs at approximately 250K – 260K. Upon cooling, the NiTi lattice transitions from a cubic to a rhombohedral structure regardless of the presence of the external magnetic field. However, upon heating the sample back to 300K, we see two cases. In the first case, the lattice transitions from rhombohedral to a cubic structure in the presence of the external magnetic field. For the second case, the lattice transitions from rhombohedral to a monoclinic structure without the external magnetic field. We also found that when subjected to this external magnetic field, the phase transition during cooling is not as abrupt, i.e. an external magnetic field softens the typically first order phase transition. Our study suggests that magnetic fields can indeed be used to affect the phase transition of NiTi and this idea may extend to other SMAs as well.