Effects of Ni addition on the magnetostriction and microstructures of Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys

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Effects of Ni addition on the magnetostriction and microstructures of

Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys

Yin-Chih Lin and Chien-Feng Lin

Citation: J. Appl. Phys. 111, 07A902 (2012); doi: 10.1063/1.3669915 View online: http://dx.doi.org/10.1063/1.3669915

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Effects of Ni addition on the magnetostriction and microstructures of

Fe

702x

Pd

30

Ni

x

high-temperature ferromagnetic shape memory alloys

Yin-Chih Lin1,a)and Chien-Feng Lin2

1

Department of Mold and Die Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan

2

Department of Mechanical and Automatic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung, Taiwan

(Presented 31 October 2011; received 10 September 2011; accepted 26 September 2011; published online 3 February 2012)

This study investigated the effects of adding a third alloying element, Ni, to create Fe70xPd30Nix

(x¼ 2, 4, 6, and 8 at. % Ni) ferromagnetic shape memory alloys. The Ni replaced a portion of the Fe. The magnetostriction and microstructures of Fe_70xPd30Nix high-temperature ferromagnetic

shape memory alloys were studied in detail. Investigation of the magnetostriction and microstructures indicated that the greater Ni amount in the Fe70xPd30Nix alloys caused the

less saturation magnetostriction at room temperature (RT); it was also observed that it was more difficult to generate an annealed recrystallization. However, greater Ni addition into the Fe70-xPd30Nix (x¼ 6 and 8 at. % Ni) alloys, the L10þ L1m twin phase decomposition into

stoichiometric L10þ L1mþ abct structures could be suppressed when the alloys were aged at

500C for 100 h. The result was that the Fe70xPd30Nix(x¼ 6 and 8 at. % Ni) alloys maintained a

high magnetostriction and magnetostrictive susceptibility (Dkks/DH) after the 500C/100 h aged

treatment. This magnetic property of the Fe_70xPd30Nix(x¼ 6 and 8 at. % Ni) alloys is suitable for

application in a high temperature (T > 500C) and high frequency environment.VC 2012 American

Institute of Physics. [doi:10.1063/1.3669915]

Magnetic field control of the high-temperature shape mem-ory effect was recently suggested as a principle for operation of a new type of actuator material. At present, a new class of high-temperature shape memory alloys (HTSMAs) has been widely investigated due to their ability to suppress transition at high temperatures exceeding 400C. This magnetic property makes HTSMAs suitable for actuation in the high-temperature environments commonly experienced in the aerospace, automo-tive, and oil industries or in other devices.1,2

Figure1shows the saturation magnetostriction (ks) versus

magnetic field (H), ks-H curves, measured at room temperature

(RT) of the as-received Fe_70xPd30Nix(x¼ 2, 4, 6, and 8 at. %

Ni) alloys. The saturation magnetostriction ks is evaluated as

ks¼ (2/3) [(kk)(k\)], where kk(k\) is the magnetostriction in

the longitudinal direction with a magnetic field parallel (perpen-dicular) to the sample’s longitude.3,4It can be seen in Fig. 1

that the saturation magnetostriction of the as-received Fe68Pd30Ni2(2 at. % Ni) alloys (48 106) is larger than that

of the as-received Fe62Pd30Ni8 (8 at. % Ni) alloys

(36.7 106). In Fig.1, the saturation magnetostriction of the as-received Fe_70xPd30Nixalloys reveals that greater Ni

addi-tion into the alloys results in less saturaaddi-tion magnetostricaddi-tion. Figure 2 shows the magnetostrictive strains of the Fe_70xPd30Nix (x¼ 2, 4, 6, and 8 at. % Ni) alloys

homoge-nized and then strain-forged to a38% reduction, solution-treated (ST) and annealed at 1100C for 8 h for recrystalliza-tion, and then followed by quenching in ice brine. k_kdenotes (DL/L)_kwith a magnetic applied field parallel to the sample’s

longitude, and k\ denotes (DL/L)\ with a magnetic applied

field normal to the sample’s longitude. Two typical k_kand k\

curves as a function of magnetic applied field can be seen in Fig.2. The magnetostriction k_ksand k\swith magnetostrictive

susceptibility (Dk_ks/DH) are plotted as a function of applied field (H) at RT (300 K) for the various Ni-content samples, indicating the following: k_ks¼ 88 106, k\s¼ 26 106

for Fe68Pd30Ni2 (2 at. % Ni) alloys; kks¼ 77 106,

k\s¼ 20 106 for Fe66Pd30Ni4 alloys; kks¼ 66 106,

k\s¼ 16 106 for Fe64Pd30Ni6 alloys; and

kks¼ 57 106, k\s¼ 15 106 for Fe62Pd30Ni8(8 at. %

Ni) alloys, respectively. However, the magnetostriction of the Fe70Pd30 alloy without added Ni is (kks¼ 51 106;

k\s¼ 10 106). It is obvious that doping Fe70Pd30alloys

with Ni can substantially improve the magnetostriction of the alloys at RT. The magnetostrictive strains of the Fe68Pd30Ni2

(2 at. % Ni) alloys (k_ks¼ 88 106, k\s¼ 26 106) were

higher than those of the Fe62Pd30Ni8 (8 at. % Ni) alloys

(k_ks¼ 57 106, k\s¼ 15 106). The magnetostriction

investigation indicates that, at RT (300 K), the magnetostric-tive strains decrease with increases in Ni content as the Fe_70xPd30Nixalloys are strain-forged to a 38% reduction

in thickness and then annealed for recrystallization at 1100C for 8 h and quenched in ice brine.

For alloys strain-forged to a38% reduction in thickness and ST and recrystallization annealed at 1100C for 8 h, the most important result of high-temperature (500C/100 h) aged Fe_70xPd30Nixalloys is shown in Fig.3. The magnetostrictive

strains k_ksand k\sare plotted as a function of applied field (H)

at RT for the various Nicontent samples, indicating the fol-lowing: k_ks¼ 16 106, k\s¼ 4 106 for Fe68Pd30Ni2 a)_{Author to whom correspondence should be addressed. Electronic mail:}

[email protected]. FAX:þ886-73835015.

0021-8979/2012/111(7)/07A902/3/$30.00 111, 07A902-1 VC2012 American Institute of Physics

JOURNAL OF APPLIED PHYSICS 111, 07A902 (2012)

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(2 at. % Ni) alloys; kks¼ 22 106, k\s¼ 7 106 for

Fe66Pd30Ni4 alloys; kks¼ 56 106, k\s¼ 12 106 for

Fe64Pd30Ni6 alloys; and kks¼ 57 106, k\s¼ 16 106

for the Fe62Pd30Ni8(8 at. % Ni) alloys, respectively. The

mag-netostrictive strains of the Fe70xPd30Nix(x¼ 2 and 4 at. % Ni)

alloys after aging at 500C for 100 h with a decrease in magne-tostriction and magnetostrictive susceptibility (Dkks/DH) are

shown in Fig. 3. The XRD and SEM analyses of the corre-sponding two aged alloys revealed the appearance of the abct

phase as well as with the decomposition of L10þ L1m twin

phase into stoichiometric L10þ L1mþ abctstructures, as shown

in Figs.4(a)–4(b)and Figs.5(a)–5(b). However, the magneto-strictive strains of the Fe70xPd30Nix (x¼ 6 and 8 at. % Ni)

alloys after aging at 500C for 100 h maintained a high magne-tostriction and magnetostrictive susceptibility, as shown in

Fig. 3. The XRD and SEM analyses revealed that these high Ni-content alloys, after 500C/100 h aging treatment, had a complete absence of the abct phase and the decomposition of

L10þ L1m twin phase into stoichiometric L10þ L1mþ abct

structures also disappeared in the latter two aged samples, as shown in Figs. 4(c)–4(d) and Figs. 5(c)–5(d). The magnetic property demonstrates that the Fe64Pd30Ni6 and Fe62Pd30Ni8

alloys are suitable for application in a high temperature (T > 500C) and high frequency environment.5

Figures4(a)–4(d) represent a series of x-ray diffraction (XRD) patterns of the Fe_70xPd30Nixalloys strain-forged to

a 38% reduction in thickness, ST at 1100_{C for 8 h, and}

aged at 500C for 100 h. Shown in Figs.4(a)–4(b) are the XRD patterns of the Fe68Pd30Ni2and Fe66Pd30Ni4alloys ST

and aged at 500C for 100 h, in which the reflections are comprised of two phases (L10þ L1m), with the main

diffrac-tion peaks being the reflecdiffrac-tion of (111)L10 and (101)L1m.

These XRD patterns also show that the (101)abct peak

appears in a diffraction angle 2h¼ 44.60 _{in Fig.}_4(a) _and

2h¼ 44.52 _{in Fig.} _4(b)_{, along with many new diffraction}

peaks revealed in the diffraction patterns. These phenomena demonstrate that the decomposition of L10þ L1mtwin phase

into stoichiometric L10þ L1mþ abct structures occurred in

these 500C/100 h aged Fe70–xPd30Nix (x¼ 2 and 4 at. %

Ni) alloys, which led to low magnetostriction, as shown in Fig. 3. The XRD patterns of the strain-forged Fe64Pd30Ni6

and Fe62Pd30Ni8alloys after ST at 1100C for 8 h then aging

at 500C for 100 h are shown in Figs.4(c)and4(d). An anal-ysis of Fig. 4(c) with Fig.4(d) reveals no (101)abct peak in

the x-ray diffraction patterns, in which we also cannot observe any new diffraction peaks in the diffraction patterns. These phenomena indicate that the decomposition of L10þ L1m twin phase into stoichiometric L10þ L1mþ abct

structures was suppressed after the strain-forged Fe_70xPd

30-Nix(x¼ 6 and 8 at. % Ni) alloys were ST and then aged at

FIG. 2. (Color online) The linear magnetostriction (106) at RT (300 K) in parallel (kk) and normal (k\) applied field (H (kOe)) to sample’s

longi-tude of the Fe70xPd30Nix(x¼ 2, 4, 6, and 8 at. % Ni) alloys strain-forged to

a 38% reduction in thickness and then solution-treated (ST) and recrystallization-annealed at 1100_{C for 8 h.}

FIG. 3. (Color online) The linear magnetostriction (106_{) at RT (300 K)}

in parallel (kk) and normal (k\) applied field (H (kOe)) to sample’s

longi-tude of the Fe70xPd30Nix(x¼ 2, 4, 6, and 8 at. % Ni) alloys strain-forged to

a 38% reduction in thickness and solution-treated (ST) and recrystallization-annealed at 1100C for 8 h, quenched in ice brine, and then aged at 500C for 100 h.

FIG. 1. (Color online) The linear saturation magnetostriction ks(106) vs

magnetic field (H) ks–H curves measured at room temperature of the

as-received Fe70xPd30Nix(x¼ 2, 4, 6, and 8 at. % Ni) alloys.

07A902-2 Y.-C. Lin and C.-F. Lin J. Appl. Phys. 111, 07A902 (2012)

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500C for 100 h, which maintained a higher magnetostric-tion, as shown in Fig.3. The XRD study result demonstrates that with more Ni addition in the Fe_70xPd30Nix(x¼ 6 and 8

at. % Ni) alloys, the separation of L10þ L1mtwin phase into

stoichiometric L10þ L1mþ abctstructures can be suppressed

after aging treatment of 500C/100 h and improve the ferro-magnetic shape memory effect (FSME) at high temperature.

Shown in Figs. 5(a)–5(b) are SEM microstructures of the Fe68Pd30Ni2 and Fe66Pd30Ni4 alloys homogenized

through strain forging and recrystallization annealing (i.e., ST) at 1100C for 8 h, and then aged at 500C for 100 h. The decomposition of the L10þ L1mtwin phase into

stoichi-ometric L10þ L1mþ abct structures, indicated by an arrow,

is apparent in both aged samples. The lamellar stoichiomet-ric L10þ L1mþ abctstructures are similar to pearlite, but

x-ray diffraction pattern analysis confirms that these lamellar structures contained L10þ L1mþ abctphases, shown in Figs.

4(a)–4(b). Magnetostriction measurement indicated that these L10þ L1mþ abct structures had low magnetostrictive

strains, as illustrated in Fig. 3. Figures 5(c)–5(d) are SEM images of the Fe64Pd30Ni6and Fe62Pd30Ni8alloys

homoge-nized and strain-forged through recrystallization annealing at 1100C for 8 h and then aged at 500C for 100 h. The decomposition of the L10þ L1m twin phase into

stoichio-metric L10þ L1mþ abct structures is not evident in these

SEM images. X-ray diffraction patterns also indicate that the Fe70xPd30Nixalloy addition of Ni (Ni¼ 6 and 8 at. %) after

strain forging, ST, and aging at 500C for 100 h can suppress the L10þ L1mtwin phase separation into the stoichiometric

L10þ L1mþ abctstructures, as shown in Figs.4(c)–4(d). As

a result, the Fe64Pd30Ni6(6 at. % Ni) and Fe62Pd30Ni8(8 at.

% Ni) alloys after strain forging, ST, and aging at 500C for 100 h maintain a high magnetostrictive strain and magneto-strictive susceptibility (Dkks/DH), as demonstrated in Fig.3.

Magnetostriction measurement indicates that the Fe70xPd30Nix alloys with greater Ni addition cause a

decrease in magnetostriction at room temperature (RT). The higher Ni addition in the Fe70xPd30Nix(x¼ 6 and 8 at. %

Ni) alloys increases magnetostriction and magnetostrictive susceptibility (Dkks/DH) when the alloys are strain-forged,

ST, and aged at high temperature (500C) for 100 h. The reason is that the decomposition of L10þ L1m twin phase

into the stoichiometric L10þ L1mþ abct structures can be

suppressed after the 500C/100 h aging treatment; therefore, the high Ni-content Fe70xPd30Nix (x¼ 6 and 8 at. % Ni)

alloys are suitable application for high temperature (T > 500C) and high frequency environments. The low Ni-content Fe70xPd30Nix(x¼ 2 and 4 at. % Ni) alloys

strain-forged, ST, and aged at 500C for 100 h generate the decom-position of L10þ L1m twin phases into the stoichiometric

L10þ L1mþ abct structures, which lead to a decrease of

magnetostriction, as confirmed by SEM, XRD, and magneto-strictive meter setup, all of which are consistent.

1

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2_{Y. Xin, Y. Li, and Z. Liu,}_{Scr. Mater.}_{63, 35 (2010).}

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(2011).

4

Y. C. Lin and H. T. Lee,J. Magn. Magn. Mater.322, 197 (2010).

5_{K. C. Atli, I. Karaman, R. D. Noebec, and H. J. Maierd,}_{Scr. Mater.}_{64, 315}

(2011).

FIG. 5. (a)-(d). SEM images of the Fe70xPd30Nix(x¼ 2, 4, 6, and 8 at. %

Ni) alloys strain-forged to a38% reduction in thickness through solution-treated (ST) and annealed recrystallization at 1100_{C for 8 h, then aged at} 500_{C for 100 h.}

FIG. 4. X-ray diffraction (XRD) patterns: (a) Fe68Pd30Ni2(2 at. % Ni), (b)

Fe66Pd30Ni4, (c) Fe64Pd30Ni6, and (d) Fe62Pd30Ni8alloys strain-forged to a

38% reduction in thickness, solution-treated (ST) at 1100_{C for 8 h,} quenched in ice brine, and aged at 500_{C for 100 h (41.14}_denotes diffrac-tion angle 2h¼ 41.14_).

07A902-3 Y.-C. Lin and C.-F. Lin J. Appl. Phys. 111, 07A902 (2012)

Effects of Ni addition on the magnetostriction and microstructures of Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys

Effects of Ni addition on the magnetostriction and microstructures of

Fe70−xPd30Nix high-temperature ferromagnetic shape memory alloys

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Effects of Ni addition on the magnetostriction and microstructures of

Fe

Pd

Ni

high-temperature ferromagnetic shape memory alloys