Measurement of Thermal Expansion Coefficient of 18&lt;i&gt;R&lt;/i&gt;-Synchronized Long-Period Stacking Ordered Magnesium Alloy

Yasuda, Nobuhiro; Kimura, Shigeru

doi:10.2320/matertrans.m2016078

Cited by 12 publications

(5 citation statements)

References 15 publications

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“…The calculated result in Fig. 7(a) indicates the possibility of a transformation from hcp-Mg to an 18R structure above 420 K. This transformation has not been observed experimentally in pure Mg, 19) probably because of the high activation energy required for atomic displacement, as discussed in the previous work. 5) The following calculation was performed to make a case for a change in the lattice constant of the hcp-Mg by the release of a solution of Y and Zn from the D0 3 phase.…”

Section: Analysis Of Xrd Patternssupporting

confidence: 50%

“…A clear gap in the a value is observed, which almost coincides with the difference in the lattice parameter between the hcp and 18R-type LPSO structures observed in the MgYZn system. 19) The c value estimated from the (0002) hcp peaks collected over the entire experimental temperature range is shown by a gray cross in Fig. 3(b).…”

Section: Analysis Of Xrd Patternsmentioning

confidence: 99%

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Key Factor for the Transformation from hcp to 18R-Type Long-Period Stacking Ordered Structure in Mg Alloys

et al. 2019

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Cast Mg 85 Y 9 Zn 6 has an 18R-type LPSO structure. However, Mg 85 Y 9 Zn 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). The D0 3 /hcp structure transformed to 18R-type LPSO during heating at ambient pressure. 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. 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. After the volume expansion of 2H lattice, the structure collapsed due to insert of random stacking faults (SFs). Then, a formation of 18R-type LPSO structure occurred. Based on a first-principles calculation for pure Mg, volume expansion of the 2H lattice causes the transformation to an 18R structure. Furthermore, the results of free energy calculations for the hcp and fcc structures in the MgYZn ternary system show that the segregation of Y and Zn atoms on SFs occurs by the Suzuki effect. These segregated Y and Zn atoms in SF layers, which have a local fcc structure, create a synergy between the stacking and chemical modulations. 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. [

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Section: Analysis Of Xrd Patternssupporting

confidence: 50%

Section: Analysis Of Xrd Patternsmentioning

confidence: 99%

Key Factor for the Transformation from hcp to 18R-Type Long-Period Stacking Ordered Structure in Mg Alloys

et al. 2019

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“…Diffraction experiments were performed with using a high precision diffractometer at the BL40XU beamline of SPring-8 [4]. A Gandolfi camera attachment was used to obtain fine diffraction patterns from oriented Mg 97 Zn 1 Y 2 alloy polycrystals [1]. The X-ray beam generated from the helical undulator was monochromatized with the Si(111) channel cut monochrometor and shaped by 150 × 150 μm 2 slits.…”

Section: Methodsmentioning

confidence: 99%

“…For structural materials, the thermal expansion often crucially affects mechanical strength. Recently, we succeeded to determine the thermal expansion coefficient of a single-phase 18R-LPSO Mg 85 Zn 6 Y 9 alloy [1]. This was achieved to use newly developed Gandolfi camera at the SPring-8 BL40XU.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Thermal Expansion Coefficient of MgZnY Alloys with Synchronized Long-Period Stacking Ordered Phase

Kimura

Yasuda

2018

MSF

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We measured the thermal expansion coefficients of 18R-LPSO phase and α-Mg phase in a Mg97Zn1Y2 alloy polycrystal. This was achieved by using a Gandolfi camera, which was attached on a high precision diffractometer at SPring-8 BL40XU beamline. By using this system, fine diffraction data were obtained from a Mg97Zn1Y2 polycrystal at 6 different temperatures between 90 and 450 K. We succeeded to determine cell parameters of 18R-LPSO phase and α-Mg phase separately in the Mg97Zn1Y2 alloy polycrystal. The thermal expansion coefficients were determined from the refined cell parameters. The differences of the thermal expansion coefficients of 18R-LPSO phase and α-Mg phase in the Mg97Zn1Y2 alloy were much smaller than those of single-phase 18R-LPSO and α-Mg polycrystals.

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“…This may due to the pure nickel coating of h-BN partially melted into the magnesium melt after the addition of h-BN particles. Studies have shown that the LPSO structure has a lower CTE than pure magnesium and good mechanical properties [10,11]. Therefore, Y element is added to the melt to consume Ni element, where the atomic ratio of Ni and Y is 1/1.6.…”

Section: Microstructure Of H-bn+lpso/mg Compositesmentioning

confidence: 99%

Preparation and Thermal Properties of BN and LPSO Hybrid Reinforced Magnesium Matrix Composite

Xia

et al. 2021

MSF

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Hexagonal boron nitride (h-BN) is a ceramic material with high thermal conductivity (TC) and low coefficient of thermal expansion (CTE), which can improve multiple thermal properties of metal-matrix composites as a reinforcing particle, but its wettability with metal melt is very poor. In order to enhance the wettability between the h-BN and magnesium alloy melt, the electroless plating was used to coat a thin layer of pure nickel on h-BN particles, which was proved to be effective and efficient in this study. The results showed that by adding Y element to magnesium alloy melt to consume Ni element melted from the nickel-plating layer, the long period stacking ordered (LPSO) structure composed of Mg-Ni-Y was successfully formed, and the magnesium matrix composite reinforced by hybrid h-BN and LPSO structure was obtained. After ultrasonic treatment (UT), the TC of the magnesium composite containing 3 vol% h-BN and 14.16 vol% LPSO is 99.92 W/(m·K), which is a 8.3% enhancement compare to the composite without UT. The average CTE (293-373 K) of the composite is 18.36×10-6 K-1, which is reduced by 29.4% compared with pure magnesium.

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Measurement of Thermal Expansion Coefficient of 18<i>R</i>-Synchronized Long-Period Stacking Ordered Magnesium Alloy

Cited by 12 publications

References 15 publications

Key Factor for the Transformation from hcp to 18R-Type Long-Period Stacking Ordered Structure in Mg Alloys

Key Factor for the Transformation from hcp to 18R-Type Long-Period Stacking Ordered Structure in Mg Alloys

Measurement of Thermal Expansion Coefficient of MgZnY Alloys with Synchronized Long-Period Stacking Ordered Phase

Preparation and Thermal Properties of BN and LPSO Hybrid Reinforced Magnesium Matrix Composite

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