DIRECT OBSERVATION OF THE PERIOD OF ALLOYS WITH LONG‐PERIOD STACKING ORDER

1966 ◽  
Vol 9 (3) ◽  
pp. 101-103 ◽  
Author(s):  
Robert S. Toth ◽  
Hiroshi Sato
Keyword(s):  
Direct Observation ◽  
Long Period ◽  
Stacking Order

Effect of Long-Period Stacking Order Phase and α-Mg Phase on Strength and Ductility of Mg-Zn-Y Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 1237-1242 ◽  
Author(s):  
Masafumi Noda ◽  
Yoshihito Kawamura
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
High Temperatures ◽  
Mg Alloys ◽  
Tensile Yield Strength ◽  
Block Type ◽  
Lpso Phase ◽  
Long Period ◽  
Stacking Order ◽  
Type Phase

Mg alloys are lightweight structural alloys that normally have a good castability and machinability as well as an excellent specific strength and rigidity. However, the mechanical properties of Mg alloys are inferior to those of Al alloys, and their range of industrial applications is limited. Recently, Mg–Zn–Y alloy has been found to show a high tensile yield strength with a good elongation. The alloy has a long-period stacking order (LPSO) phase as the secondary phase in an α-Mg phase. In general, the tensile yield strengths of LPSO-type Mg alloy are known to be markedly enhanced by the formation of kink bands in the LPSO phase and by microstructural refinement of the α-Mg phase during plastic deformation. The separate roles of the LPSO phase and the α-Mg phase in relation to the mechanical properties of high-strength LPSO-type Mg alloy were investigated at ambient and high temperatures. For high strengths at ambient and high temperatures, it was important that the α-Mg phase consisted of a fine-grain region and a nonrecrystallized region, and that the LPSO phase remained as a block-type phase. On the other hands, it was necessary to change the LPSO phase from a block-type phase into a plate-type phase by heat treatment before tensile testing to improve the ductility of the alloy while maintaining its tensile yield strength. Microstructural control of the LPSO phase and the α-Mg phase is necessary to obtained Mg–Zn–Y alloy with superior mechanical properties at ambient-to-high temperatures.

Variation of long-period stacking order structures in rapidly solidified Mg97Zn1Y2 alloy

2005 ◽  
Vol 393 (1-2) ◽  
pp. 269-274 ◽  
Author(s):  
M. Matsuda ◽  
S. Ii ◽  
Y. Kawamura ◽  
Y. Ikuhara ◽  
M. Nishida
Keyword(s):  
Long Period ◽  
Stacking Order ◽  
Rapidly Solidified ◽  
Order Structures

On the Polytypic Transformations in SiC

2012 ◽  
Vol 18-19 ◽  
pp. 89-96
Author(s):  
Maya Marinova ◽  
Alkyoni Mantzari ◽  
Ariadne Andreadou ◽  
Efstathios K. Polychroniadis
Keyword(s):  
Liquid Phase ◽  
Liquid Phase Epitaxy ◽  
Growth Conditions ◽  
Small Energy ◽  
Long Period ◽  
Stacking Order

In the present work we report on the polytypic transformations taking place in nanoscale dimensions within 6H-SiC crystals. The examined crystals were grown by Liquid Phase Epitaxy using a mixture of Si and Al as solvents. The study concentrated on the differences from the “correct” stacking order of the Si-C bilayers for 6H-SiC leading to the formation of other polytypes. A great variety of sequences was found, which resulted to the appearance of rare short and long period polytypes or individual lamellae having their “own” stacking inside the 6H-SiC matrix. These nanostructured faults which deteriorate the quality of the grown material indicate also their “sensitivity” to any small or even infinitesimal change of the growth conditions, due to the very small energy among them.

On the Nanostructure of SiC

2010 ◽  
Vol 12 ◽  
pp. 99-104
Author(s):  
Maya Marinova ◽  
Efstathios K. Polychroniadis
Keyword(s):  
Silicon Carbide ◽  
Liquid Phase ◽  
Structural Properties ◽  
Liquid Phase Epitaxy ◽  
Stacking Faults ◽  
Growth Conditions ◽  
Small Energy ◽  
Long Period ◽  
Stacking Order

The present work deals with the structural properties of silicon carbide in nanoscale dimensions. The examined crystals were 6H-SiC grown by Liquid Phase Epitaxy. The study was concentrated on the stacking faults and any other differences from the “correct” stacking order of the Si-C bilayers for this polytype. Three main types of stacking faults were observed: (i) Cubic lamellae with thickness of four and two Si-C bilayers, always occurring in reverse stacking with respect to each other and separated by at least one unit cell of 6H-SiC; (ii) “twinned” 6H-SiC lamellae separated by a two-bilayer thick cubic inclusion. As a result the sequence in the “twinned” 6H-SiC changes from (3+3-) to (3-3+). (iii) Lamellae showing fringes, the interrelated distance of which suggests inclusion with sequence (22). Further, a high variety of sequences was found, leading to the appearance of rare long period polytypes or individual lamellae having their “own” stacking inside the 6H-SiC matrix. These nanostructured faults which deteriorate the quality of the grown material indicate also their “sensitivity” to any small or even infinitesimal change of the growth conditions, due to the very small energy among them.

scholarly journals Precipitates with Peculiar Morphology Consisting of a Disk-Shaped Amorphous Core Sandwiched between 14H-Typed Long Period Stacking Order Crystals in a Melt-Quenched Mg98Cu1Y1 Alloy

2006 ◽  
Vol 47 (4) ◽  
pp. 1264-1267 ◽  
Author(s):  
Makoto Matsuura ◽  
Kazuya Konno ◽  
Mitsuhiko Yoshida ◽  
Masahiko Nishijima ◽  
Kenji Hiraga
Keyword(s):  
Long Period ◽  
Stacking Order

Microstructures and Tensile Properties of Mg-6Gd-3Y-1.4Zn-0.4Zr Alloys

2016 ◽  
Vol 849 ◽  
pp. 148-153
Author(s):  
Cen Huang ◽  
Chu Ming Liu ◽  
Bi Zheng Wang
Keyword(s):  
Peak Hardness ◽  
Multidirectional Forging ◽  
Long Period ◽  
Stacking Order ◽  
A Value ◽  
Lpso Structure ◽  
Average Grain Size ◽  
Cumulative Strain ◽  
Cast Specimen ◽  
Peak Aged

Microstructures and tensile mechanical properties of Mg–6Gd–3Y–1.4Zn–0.4Zr (wt.%) alloy were systematically studied. Three phases were found in the as-cast specimen: α-Mg, Mg5(GdYZn), Mg12(GdY)Zn. The long-period stacking order (LPSO) structure was found in the alloy, which is the phase of Mg12(GdY)Zn. Two LPSO structures with different images were found in the homogenized alloys: the block-shaped ones at grain boundaries and needle-like ones in the inner grains. The homogenized Mg–6Gd–3Y–1.4Zn–0.4Zr (wt.%) alloy was subjected to multidirectional forging (MDF) at 480°C. It was shown that the average grain size decreased to ~5.2μm after 9 passes with the cumulative strain of 2.7. The ageing hardening behavior of as-forged specimens at 200°C has been investigated. Peak hardness was obtained after 26 h, with a value of 110 HV. The ultimate tensile strengths of the as-forged and peak-aged alloys were 398 MPa and 431 MPa, the yield strengths were 351MPa and 398MPa, and the elongations were 11.24% and 8% respectively.

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