Development of Microstructures of Long-Period Stacking Ordered Structures in Mg85Y9Zn6 Alloys Annealed at 673 K (400 °C) Examined by Small-Angle X-Ray Scattering

Abstract

Development of LPSO structure and in-plane ordering during annealing the Mg85Y9Zn ternary alloy sample at 673 K (400°C) was examined by synchrotron radiation small-angle scattering/ diffraction measurements. By examining the first diffraction peaks for 18R, 10H, and in-plane order spot, the growth kinetics of in-plane order domain and the transition from 10H into 18R were discussed. The domain growth of in-plane order was characterized by small domain with little correlation between neighboring segregation layers.

Stability of Long-Period Stacking Ordered Structures at Elevated Temperatures Examined by Multicolor Synchrotron Radiation X-ray Scattering/Diffraction Measurements

“…The microstructure change is similar to the one observed for 1-2 samples. 25) As reported in the previous work on 6-9 and 1-2 alloys, 16,25) the peaks at 3.4 nm ¹1 , 4 nm ¹1 and 4.8 nm ¹1 correspond to compositional modulation of 14H, 18R and 10H stacking orders. The broad peak appearing between 5 nm ¹1 and 6 nm ¹1 is the interference between L1 2 clusters in the segregated layers.…”

“…The broad peak appearing between 5 nm ¹1 and 6 nm ¹1 is the interference between L1 2 clusters in the segregated layers. 16,17,24) During heating, the main LPSO periodicity appearing in the sample was 18R for the 3-5 composition, and weak 10H are also observed in the as-cast sample. The 10H peak disappeared at lower temperatures than 18R did, due to relative instability.…”

“…is much slower than the initial mold casting. Considering that the reported stable periodicity for the sample having ¡-Mg + LPSO two phase microstructure is 14H, 15,25) higher cooling rate in the L+¡-Mg region leads to insufficient mixing in the liquid region and formation of LPSO at higher concentration. The peak position corresponding to the in-plane ordering is much lower than the ideal 2 ffiffi ffi 3 p a position, 4) as reported for 6-9 and 1-2 alloys.…”

Small-angle X-ray scattering analysis on the in-plane cluster distribution during heating amorphous Mg85Y9Cu6 alloys

“…[1][2][3][4][5][6] Detailed LPSO structures with nearly perfect order have been examined using electron microscopes, [7][8][9][10][11][12][13][14] first-principles calculations, [15][16][17][18] and other techniques. [19][20][21][22][23] For such ideal cases, LPSO structures are characterized by periodic stacking faults in the c-planes of the hcp Mg lattice, where Zn 6 Y 8 -Mg, so-called L1 2 clusters, 7,[10][11][12][13][14][15][16] are aligned as 2√3 × 2√3 two-dimensional superstructures. However, in MgYZn alloys, less-ordered samples with well-defined signatures of LPSO structures, that is, sharp diffraction peaks of 18R or 10H stacking and diffuse six-hold cluster arrangements, are commonly observed, suggesting that the average cluster-cluster distance can be loose and change smoothly during annealing.…”

“…However, in MgYZn alloys, less-ordered samples with well-defined signatures of LPSO structures, that is, sharp diffraction peaks of 18R or 10H stacking and diffuse six-hold cluster arrangements, are commonly observed, suggesting that the average cluster-cluster distance can be loose and change smoothly during annealing. [17][18][19][20][21] This leads to the idea of a cluster solution for stacking faults. Kimizuka et al 17,18) performed first-principles calculations for clustercluster interactions and coarse-grained Monte Carlo simulations to explain the differences in the in-plane cluster arrangements between MgYAl and MgYZn alloys.…”