SPring-8 における Mg 基 LPSO 相の弾性的性質の研究
ESISM, 神戸大工学研究科 田中克志，神戸大院 上野彰宣，JASRI 筒井智嗣，A.Q.R. BaronLong Period Stacking Ordered phasehas been founded in Mg-Zn-Y alloy

Measurement of Elastic Properties
Inelastic X-ray scattering

The structure of LPSO phases

EL

Scattered X-rayks, ℏωsIncident X-ray

T1
T2

Phononkp, ℏωpki , ℏωik s = k i + kp

Kishida et al. Intermetallics Vol. 31 (2012) 55

Typical polytypes of LPSO phase-π/a0π/akDispersion of phononsℏω s= ℏω i + ℏωp Energy conservation principle

Inoue et al. J. Mater. Res. Vol. 16 (2001) 1894

Elastic stiffness constants of Mg-based LPSO phase with the 14H structure (Hexagonal)

This precipitate significantly improve bothstrength and elongation of Mg based alloys

 c11
 c12
c 13TM, RE enriched layers

Extensive investigations are carrying out.

Pure Mg layers

The phase is formed in Mg-TM-RE system
TM: Al, Co, Ni, Cu, Zn
RE: Y, Dy, Ho, Er, Gd, Tb, Tm
10H

18R

14H

c12

c13c 22c 23c 23c330c 440c55
c66 c11  c12c66 2Five independent elastic constants

Relationship between energy of phonon at around the  point and elastic constants
k12 c11  k 22

Sample preparation
Mg

Momentum conservation principle

c11  c12
 k32 c44   22c c
k1k 2 11 122
k1k3 c13  c44 

k1k 2

c11  c122

k1k3 c13  c44 

c11  c12
 k 22 c11  k32 c44   2
2k 2 k3 c13  c44 k12

k 2 k3 c13  c44 k  k c  k c  21224423 33

02YZnAr+SF6Induction heating
A small single crystal was cut out(20 X 30 X 100 μm 3 )pure-MgO crucible

Measurement of superlatice reflections (00l)

１４H
１８R
Baron et al. J. Phys. Chem. Solids Vol. 61 (2000) 461

100μm
Microstructure of Mg-5at.%Zn-7at%Y alloyℏωi ~ ℏωs ~ 22keV Resolution ~1.5meV

Angular frequency / Trad s-1

Intensity (arb. unit)

Examples of measured IXS spectrums

40353025201510501614121086420[0] Longitudinal-1v = 5751 ms

048

Wave number / (nm) -1

2520v = 6164 ms15v = 2618 ms

0246All independent elastic constants are determined as-1

1050012[0] Transverse on (002)-1

Least square fitting for all measured phonon peaks[00] Longitudinal30345/ GPa

C 11C 12C 44

78.7±1.2

27.2±1.4

16.3±0.6

Wave number / (nm) -1
Angular frequency / Trad s-1

Angular frequency / Trad s-1

Results

Angular frequency / Trad s-1

Major phase is the 14H stacking structure

Wave number / (nm) -1[0] Transverse on (110)141210v = 3595 ms8-16C 33

4200123

Wave number / (nm) -1

493.7±2.5

C 13C 6626.8±1.925.7/ GPa

Dispersion of phonons

Poly-crystalline elastic constants are calculated as

Energy transfer / meV
Functions for peak fitting:Pseudo elastic scattering: delta function
Phonon: Dumped harmonic oscillator

Discussion

Elastic constants were roughly estimated
C 11
C 33
C 44
C 66
/ GPa

Convoluted with Lorentz function(Resolution function)

Is the LPSO phase a composite of pure-Mgand (Zn, Y) enriched layers?

Elastic constants of pure-Mg
C 11

C 12

C 44

59.3

25.7

16.4

C 33

C 13

C 66

61.5

21.4

16.8

71.1

83.2

15.0

28.2

Comparing with the macroscopic measurement(Resonant Ultrasound Spectroscopy)

Shearmodulus

57.4

22.2

Bulk
modulus / GPa
45.7

Future works
Measurements for LPSO phases with otherstacking sequence/ GPa
Poly-crystal/ GPa

Piezo-electrictransducers

To separate the elastic properties ofpure-Mg and (Zn, Y) enriched layers
Measurements for LPSO phases with otheralloying elements

Most of elastic stiffness constants of LPSO
phase are larger than those of pure-Mg

Inter-atomic bondings are strengthened
upon alloying with Zn and Y

Young’ smodulus

C 44 < C 66 but

C 11 < C 33

LPSO phase is not a simple composite ofpure-Mg and (Zn, Y) enriched layers

Young’ smodulusShear
modulus

53.4

20.9

Bulkmodulus / GPa
40.2

To understand what is the common
elastic propertis of LPSO phases