Details
| Original language | English |
|---|---|
| Pages (from-to) | 614-635 |
| Number of pages | 22 |
| Journal | Advanced Engineering Materials |
| Volume | 14 |
| Issue number | 8 |
| Publication status | Published - 23 Jul 2012 |
| Externally published | Yes |
Abstract
Magnetic shape memory alloys (MSMAs), exhibit large strains and hence are materials, which could substitute giant magnetostrictive and piezoelectrical materials in actuating devices. The actuation stress needed to induce the strain is much lower than in other actuator materials. Since the strain can be induced without phase transformation by a magnetic field, the development of actuators with high working frequencies is possible. However, for reasonable applications, large strains have to be induced with small magnetic fields. Up to now repeatable magnetically induced strains of 5-10% in magnetic fields of less than 500 mT have been achieved only in single crystals. The production of Ni-Mn-Ga based single crystals is difficult and time consuming. The crystal quality is affected by porosity and impurities. With the Bridgeman based method called Slag Remelting and Encapsulation (SLARE) single crystalline ingots of Ni-Mn-Ga, Ni-Mn-Ga-Fe, and Ni-Mn-Ga-Co of high quality were grown and characterized. The results show that MSMA properties depend on the position within the single crystalline rods due to a composition gradient. The influence of surface treatment demonstrates that the decrease of surface roughness leads to a decrease of twinning stress. MSMAs with twinning stresses above 1 MPa show a magnetic field induced strain (MFIS) when tilting is not restricted by constraints. Softer samples can adapt to constraints much better and show large MFIS. Substituting Ni by Fe and Co, shifted the phase transitions successfully to higher temperatures. Ni-Mn-Ga alloyed with up to 6 at.% Co showed three different martensite structures: a non-modulated tetragonal structure, a modulated tetragonal structure, showing the same behavior as Ni-Mn-Ga with identical structures and a non-modulated orthorhombic structure with a stress-strain-behavior explainable by the double twinning mechanism.
ASJC Scopus subject areas
- Materials Science(all)
- General Materials Science
- Physics and Astronomy(all)
- Condensed Matter Physics
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In: Advanced Engineering Materials, Vol. 14, No. 8, 23.07.2012, p. 614-635.
Research output: Contribution to journal › Review article › Research › peer review
}
TY - JOUR
T1 - Key properties of Ni-Mn-Ga based single crystals grown with the SLARE technique
AU - Rolfs, Katharina
AU - Chmielus, Markus
AU - Guldbakke, Jan M.
AU - Wimpory, Robert C.
AU - Raatz, Annika
AU - Petry, Winfried
AU - Müllner, Peter
AU - Schneider, Rainer
PY - 2012/7/23
Y1 - 2012/7/23
N2 - Magnetic shape memory alloys (MSMAs), exhibit large strains and hence are materials, which could substitute giant magnetostrictive and piezoelectrical materials in actuating devices. The actuation stress needed to induce the strain is much lower than in other actuator materials. Since the strain can be induced without phase transformation by a magnetic field, the development of actuators with high working frequencies is possible. However, for reasonable applications, large strains have to be induced with small magnetic fields. Up to now repeatable magnetically induced strains of 5-10% in magnetic fields of less than 500 mT have been achieved only in single crystals. The production of Ni-Mn-Ga based single crystals is difficult and time consuming. The crystal quality is affected by porosity and impurities. With the Bridgeman based method called Slag Remelting and Encapsulation (SLARE) single crystalline ingots of Ni-Mn-Ga, Ni-Mn-Ga-Fe, and Ni-Mn-Ga-Co of high quality were grown and characterized. The results show that MSMA properties depend on the position within the single crystalline rods due to a composition gradient. The influence of surface treatment demonstrates that the decrease of surface roughness leads to a decrease of twinning stress. MSMAs with twinning stresses above 1 MPa show a magnetic field induced strain (MFIS) when tilting is not restricted by constraints. Softer samples can adapt to constraints much better and show large MFIS. Substituting Ni by Fe and Co, shifted the phase transitions successfully to higher temperatures. Ni-Mn-Ga alloyed with up to 6 at.% Co showed three different martensite structures: a non-modulated tetragonal structure, a modulated tetragonal structure, showing the same behavior as Ni-Mn-Ga with identical structures and a non-modulated orthorhombic structure with a stress-strain-behavior explainable by the double twinning mechanism.
AB - Magnetic shape memory alloys (MSMAs), exhibit large strains and hence are materials, which could substitute giant magnetostrictive and piezoelectrical materials in actuating devices. The actuation stress needed to induce the strain is much lower than in other actuator materials. Since the strain can be induced without phase transformation by a magnetic field, the development of actuators with high working frequencies is possible. However, for reasonable applications, large strains have to be induced with small magnetic fields. Up to now repeatable magnetically induced strains of 5-10% in magnetic fields of less than 500 mT have been achieved only in single crystals. The production of Ni-Mn-Ga based single crystals is difficult and time consuming. The crystal quality is affected by porosity and impurities. With the Bridgeman based method called Slag Remelting and Encapsulation (SLARE) single crystalline ingots of Ni-Mn-Ga, Ni-Mn-Ga-Fe, and Ni-Mn-Ga-Co of high quality were grown and characterized. The results show that MSMA properties depend on the position within the single crystalline rods due to a composition gradient. The influence of surface treatment demonstrates that the decrease of surface roughness leads to a decrease of twinning stress. MSMAs with twinning stresses above 1 MPa show a magnetic field induced strain (MFIS) when tilting is not restricted by constraints. Softer samples can adapt to constraints much better and show large MFIS. Substituting Ni by Fe and Co, shifted the phase transitions successfully to higher temperatures. Ni-Mn-Ga alloyed with up to 6 at.% Co showed three different martensite structures: a non-modulated tetragonal structure, a modulated tetragonal structure, showing the same behavior as Ni-Mn-Ga with identical structures and a non-modulated orthorhombic structure with a stress-strain-behavior explainable by the double twinning mechanism.
UR - http://www.scopus.com/inward/record.url?scp=84864692251&partnerID=8YFLogxK
U2 - 10.1002/adem.201200065
DO - 10.1002/adem.201200065
M3 - Review article
AN - SCOPUS:84864692251
VL - 14
SP - 614
EP - 635
JO - Advanced Engineering Materials
JF - Advanced Engineering Materials
SN - 1438-1656
IS - 8
ER -