ISSRNS 2016: Abstracts / Extended abstracts / Synchrotron Radiation in Natural Science Vol. 15, No. 1-2 (2016)
94
P-40
Crystallographic structure study of Fe
64Mn
30Si
6shape memory alloys
W. Prendota1*, S. Miyazawa2, T. Strączek 1, K. Goc1, Cz. Kapusta1 and A. Takasaki2
1AGH University of Science and Technology, Cracow, Poland
2Shibaura Institute of Technology, Tokyo, Japan
Keywords: Memory Shape Alloy, Memory Shape Effect
*e-mail: Witold.Prendota@fis.agh.edu.pl
Memory Shape Alloys (MSA) are the family of materials exhibiting the Shape Memory Effect (SME), which basically allows a deformed material to obtain its previous shape after subsequent heating. It is related to a martensite-to-austenite transformation (deformation) and a reverse process during heating: ε↔γ phases change. There are many systems which exhibit the SME.
The most common are Ni-Ti alloys, because they are e.g.
biocompatible and long term corrosion resistant [1]. The MSA play important role in industrial and medical applications. In order to reduce costs, the Fe-Mn-Si system has been studied.
In the Fe-Mn-Si material preparation process the iron (64 at.%; purity: 99,9%), manganese (30 at.%, purity:
99,9%) and silicon (6 at.%, purity: 99,9%) powders were mixed, mechanically alloyed (30 hours, 600 rpm, 1:8 ball to weight ratio, argon atmosphere), sintered (10 minutes, 900 °C temperature, 20 MPa uniaxial pressure, vacuum), and annealed (1 hour, 600 °C, vacuum). After deformation compression performed in uniaxial geometry parallel to the external stress of the sintering (room temperature, 1 mm/min, 4 % deformation). Last step was subsequent heating the samples in furnance to 200, 300, 400, 500 and 600°C, respectively.
In this study, X-Ray Diffraction (XRD) and X-ray Absorption Spectroscopy (XAS) in the XANES (X-ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure) ranges were used.
XRD measurements were done on Rigaku Ultima IV (Cu-Kα radiation, 0.154 nm wavelength). Synchrotron measurements were carried out at the SuperXAS beamline of the Swiss Light Source, Paul Sherrer Institute, Switzerland (partial fluorescence yield mode, room temperature).
X-Ray measurements were performed in the temperature range, starting from room temperature, up to 600°C (five temperature points) in vacuum. The results obtained are presented in Figure 1. They reveal a crystallographic structure change during heating due to the ε→γ transformation.
Figure 2 presents results of the XAS study for the unannealed sample (Room Temperature) and after 600°C heating. Fourier transforms obtained from the EXAFS part of the Fe K-edge data, reveal one main peak at 1.96 and 2.06Å for the unannealed and 600°C annealed sample, respectively.
Figure 1. Results of XRD temperature measurements.
For the Mn K-edge EXAFS the obtained peaks are at 2.09 and 1.99Å for the unannealed and 600°C annealed sample, respectively. Small differences observed in the XANES region can be attributed to slight changes in the electronic state of the elements.
0 2 4 6 8 10
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35
0 1 2 3 4 5 6 7 8 9 10
0,00 0,05 0,10 0,15 0,20 0,25
7050 7100 7150 7200 7250 7300 7350 7400 7450 0,0
0,2 0,4 0,6 0,8 1,0 1,2
0 1 2 3 4 5 6 7 8 9
-0,4 -0,2 0,0 0,2 0,4 0,6
6500 6550 6600 6650 6700 6750 6800 6850 6900 0,0
0,2 0,4 0,6 0,8 1,0 1,2
0 1 2 3 4 5 6 7 8 9 10
-1,0 -0,5 0,0 0,5 1,0
|Chi(R)| (Å-2)
R (Å) EXAFS_SM_S1_Mn_K_edge - Room Temp.
EXAFS_SM_S4_Mn_K_edge - 600 deg
|Chi(R)| (Å-2)
R (Å)
EXAFS_SM_S1_Fe_K_egde - Room Temp.
EXAFS_SM_S4_Fe_K_edge - 600 deg
Normalized µ(E)
Energy (eV)
EXAFS_SM_S1_Fe_K_egde - Room Temp.
EXAFS_SM_S4_Fe_K_edge - 600 deg
kChi(k) (Å-1)
k (Å-1) EXAFS_SM_S1_Fe_K_egde - Room Temp.
EXAFS_SM_S4_Fe_K_edge - 600 deg
Normalized µ(E)
Energy (eV)
EXAFS_SM_S1_Mn_K_edge - Room Temp.
EXAFS_SM_S4_Mn_K_edge - 600 deg
b)
kChi(k) (Å-1)
k (Å-1) EXAFS_SM_S1_Mn_K_edge - Room Temp.
EXAFS_SM_S4_Mn_K_edge - 600 deg
a)
Figure 2. XANES/EXAFS results obtained for room temperature and 600°C for a) Fe and b) Mn K-α.
The results obtained show that in the case of 600°C sample the dominant phase (based on XRD) is α-BCC which is consistent with the Fe and Mn K-edge XAS (1st neighbour shell at 1.96Å and 1.99 Å, respectively). In the unannealed sample the γ-phase dominates (1st neigbour shell at 2.06Å and 2.09 Å, respectively).
Acknowledgments: This work was supported partially by the Ministry of Science and Higher Education (MNiSW), Poland and Shibaura Institute of Technology, Japan.
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[1] V. P. Panoskaltsis (2013). Mechanics of Shape Memory Alloys - Constitutive Modeling and Numerical Implications, Shape Memory Alloys - Processing, Characterization and Applications, Dr. Francisco Manuel Braz Fernandes (Ed.), InTech, DOI: 10.5772/52228.
