3 ) The high strength of Mg 97Y 2Zn 1 is ascribed to a kink deformation of the LPSO structure.
CRYSTALDIFFRACT 1.4 SERIES
2 ) Mg 97Y 2Zn 1 alloys include a series of novel long-period stacking ordered (LPSO) structures synchronized with the chemical concentration, which can be classified into the 10H-, 18R-, 14H-, and 24R-types. 1 ) The σ 0.2 values of Mg 97Y 2Zn 1 alloys produced by conventional casting and extrusion exceed 320 MPa. Mg–Y–Zn ternary alloys are potential lightweight structural materials because the 0.2% proof stress (σ 0.2) of rapidly solidified powder metallurgy Mg 97Y 2Zn 1 alloys exceeds 600 MPa. The development of lightweight structural materials has received much attention, motivated by the need for energy conservation and compliance with exhaust-gas regulations for vehicles. Present result insists that the volume increase of 2H lattice takes place first, and then the transformation from the hcp structure to 18R stacking occurs. These segregated Y and Zn atoms in SF layers, which have a local fcc structure, create a synergy between the stacking and chemical modulations.
CRYSTALDIFFRACT 1.4 FREE
Furthermore, the results of free energy calculations for the hcp and fcc structures in the Mg–Y–Zn ternary system show that the segregation of Y and Zn atoms on SFs occurs by the Suzuki effect. Based on a first-principles calculation for pure Mg, volume expansion of the 2H lattice causes the transformation to an 18R structure. Then, a formation of 18R-type LPSO structure occurred. After the volume expansion of 2H lattice, the structure collapsed due to insert of random stacking faults (SFs). At first, lattice volume of 2H increased with an increase in the temperature, because of the Zn and Y emitted from the D0 3 phase into the 2H lattice. In this research, the transformation process from the D0 3/hcp structure to 18R-type LPSO structure was discussed by means of in situ XRD and first-principles calculation. The D0 3/hcp structure transformed to 18R-type LPSO during heating at ambient pressure.
However, Mg 85Y 9Zn 6 recovered after being subjected to a loading pressure of 7 GPa at 973 K shows a fine dual-phase structure composed of a face-centered cubic (fcc) structure showing a superlattice (D0 3), as well as a hexagonal close-packed structure (hcp:2H). Institute of Multidisciplinary Research for Advanced Materials, Tohoku UniversityĬast Mg 85Y 9Zn 6 has an 18R-type LPSO structure. Magnesium Research Center, Kumamoto University Geodynamics Research Center, Ehime University Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology
Department of Mechanical Engineering, Ehime University Geodynamics Research Center, Ehime Universityĭepartment of Mechanical Engineering, Ehime Universityĭepartment of Condensed Matter Physics, Institute of Physics, P.J.