| dc.contributor |
Karaman , Ibrahim |
|
| dc.creator |
Karaca , Haluk Ersin |
|
| dc.date |
2010 -01 -14T23 :58 :45Z |
|
| dc.date |
2010 -01 -16T01 :55 :31Z |
|
| dc.date |
2010 -01 -14T23 :58 :45Z |
|
| dc.date |
2010 -01 -16T01 :55 :31Z |
|
| dc.date |
2007 -08 |
|
| dc.date |
2009 -05 -15 |
|
| dc.date.accessioned |
2013 -03 -12T17 :54 :35Z |
|
| dc.date.available |
2013 -03 -12T17 :54 :35Z |
|
| dc.date.issued |
2013 -03 -12 |
|
| dc.identifier |
http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1562 |
|
| dc.identifier.uri |
http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1562 |
|
| dc.description |
The purpose of this work is to reveal the governing mechanisms responsible for the magnetic field -induced i ) martensite reorientation in Ni2MnGa single crystals , ii ) stress -assisted phase transformation in Ni2MnGa single crystals and iii ) phase transformation in NiMnCoIn alloys . The ultimate goal of utilizing these mechanisms is to increase the actuation stress levels in magnetic shape memory alloys (MSMAs ) . Extensive experimental work on magneto -thermo -mechanical (MTM ) characterization of these materials enabled us to i ) better understand the ways to increase the actuation stress and strain and decrease the required magnetic field for actuation in MSMAs , ii ) determine the effects of main MTM parameters on reversible magnetic field induced phase transformation , such as magnetocrystalline anisotropy energy (MAE ) , Zeeman energy (ZE ) , stress hysteresis , thermal hysteresis , critical stress for the stress induced phase transformation and crystal orientation , iii ) find out the feasibility of employing polycrystal MSMAs , and iv ) formulate a thermodynamical framework to capture the energetics of magnetic field -induced phase transformations in MSMAs . Magnetic shape memory properties of Ni2MnGa single crystals were characterized by monitoring magnetic field -induced strain (MFIS ) as a function of compressive stress and stress -induced strain as a function of magnetic field . It is revealed that the selection of the operating temperature with respect to martensite start and Curie temperatures is critical in optimizing actuator performance . The actuation stress of 5 MPa and work output of 157 kJm−3 are obtained by the field -induced variant reorientation in NiMnGa alloys . Reversible and one -way stress -assisted field -induced phase transformations are observed in Ni2MnGa single crystals under low field magnitudes ( <0 .7T ) and resulted in at least an order of magnitude higher actuation stress levels . It is very promising to provide higher work output levels and operating temperatures than variant reorientation mechanisms in NiMnGa alloys . Reversible field -induced phase transformation and shape memory characteristics of NiMnCoIn single crystals are also studied . Reversible field -induced phase transformation is observed only under high magnetic fields ( >4T ) . Necessary magnetic and mechanical conditions , and materials design and selection guidelines are proposed to search for field -induced phase transformation in other ferromagnetic materials that undergo thermoelastic martensitic phase transformation . |
|
| dc.format |
electronic |
|
| dc.format |
application /pdf |
|
| dc.format |
born digital |
|
| dc.language |
en _US |
|
| dc.subject |
magnetic shape memory alloys |
|
| dc.subject |
ferromagnetic shape memory alloys |
|
| dc.subject |
phase transformation |
|
| dc.subject |
martensitic transformation |
|
| dc.subject |
variant reorientation |
|
| dc.subject |
magnetocrystalline anisotropy energy |
|
| dc.title |
Magnetic field -induced phase transformation and variant reorientation in Ni2MnGa and NiMnCoIn magnetic shape memory alloys |
|
| dc.type |
Book |
|
| dc.type |
Thesis |
|
| dc.type |
Electronic Dissertation |
|
| dc.type |
text |
|