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Zhang, J.; Fan, Z.; Wang, Y. Q.; Zhou, Baoxue

doi:10.1023/a:1006702709371

Cited by 65 publications

(21 citation statements)

References 7 publications

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“…Mg-high Si alloys are in situ Mg metal matrix composites (MMCs) containing hard particles of Mg 2 Si [4][5][6], since a maximum solid solubility of Si into Mg is only 0.003 at.% and Si atoms react with Mg atoms and are precipitated as an intermetallic compound of Mg 2 Si [7,8]. Recently, it has being shown that Mg-Si alloys have high potential as heat resistant light metals because Mg 2 Si exhibits a high melting temperature, low density, low thermal expansion coefficient, and a reasonably high elastic modulus [6,[9][10][11]. However, ingot metallurgy (I/M) Mg-Si alloys showed very low ductility and strength because of the large Mg 2 Si particle size and brittle eutectic structures [5,7,11].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, it has being shown that Mg-Si alloys have high potential as heat resistant light metals because Mg 2 Si exhibits a high melting temperature, low density, low thermal expansion coefficient, and a reasonably high elastic modulus [6,[9][10][11]. However, ingot metallurgy (I/M) Mg-Si alloys showed very low ductility and strength because of the large Mg 2 Si particle size and brittle eutectic structures [5,7,11]. More recently, it has been reported that the mechanical properties of Mg-Si alloys could be improved by the application of advanced processing techniques such as hot extrusion (HE) [4,12,13], rapid solidification (RS) [14], directional solidification (DS) [15], and mechanical alloying (MA) [9,16].…”

Section: Introductionmentioning

confidence: 99%

“…Traditionally, many of the studies have been focused on the modification effect of rare earth elements, strontium, sodium salt, and halide salts on the eutectic and primary Si crystals in Al-Si alloys [17][18][19][20][21][22][23][24] and on Mg 2 Si in Al-Si-Mg alloys [11,[25][26][27][28], while less work has been carried on the modification effect of Mg 2 Si in Mg-Si alloys.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Modification of Mg2Si in Mg–Si alloys with K2TiF6, KBF4 and KBF4 + K2TiF6

Wang

Jiang

et al. 2005

Journal of Alloys and Compounds

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modification of Mg2Si in Mg–Si alloys with K2TiF6, KBF4 and KBF4 + K2TiF6

Wang

Jiang

et al. 2005

Journal of Alloys and Compounds

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“…1). Generally, increasing cooling rate brings on an increase in undercooling of the melts, which in turn refines the size of as-cast microstructures, as reported by Zhang et al 16) In addition, also the relatively rapid solidification restricts the growth of grains and yields fine structures. Hereby, both unmodified and KBF 4 -modified alloys can be refined with increase in cooling rate.…”

Section: Influence Of Cooling Rate On Initial As-cast Microstructurementioning

confidence: 69%

Influences of Morphology and Size of Mg2Si on Microstructural Evolution of Mg–6.2Si Alloys during Partial Remelting

et al. 2009

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After isothermally treated at 660°C for 20 min, both dendritic Mg 2 Si in unmodified alloys and polyhedral ones in KBF 4 -modified alloys transformed to nearly globular morphology, while the degree of spheroidization in KBF 4 -modified alloy was lower than that in unmodified alloy. This result might be attributed to both restriction effect of boron and stability of octahedral primary Mg 2 Si crystals. After isothermal treatment at 660°C for 20 min, however, the initial grain sizes of dendritic Mg 2 Si crystals in unmodified alloy or polyhedral ones in modified alloy obtained by different cooling rates (copper mold with the holes of f20 and f6 mm) only caused a little effect on the partial remelting microstructure. The fine primary Mg 2 Si particles obtained from f6 mm hole, however, were more readily to evolve to globular crystals, which might be attributed to the more active Ostwald ripening and/or coalescence.KEY WORDS: Mg-Si alloys; modification; grain size; partial remelting.In spite of the above, seldom investigations have been carried out on the effect of partial remelting on the microstructural evolution of modified Mg-high Si alloys. The present study is aimed to investigate the influence of as-cast microstructure, with different grain sizes and morphologies of Mg 2 Si, on the microstructural evolution of the unmodified and KBF 4 -modified Mg-6.2Si alloys during partial remelting process. Particular attention is paid to the influence of isothermal holding temperatures on the morphology evolution of KBF 4 -modified Mg-6.2Si alloy. It is expected that the preliminary work could be significant in prompting the development of Mg-high Si alloys. Experimental ProcedureIndustrial pure Mg ingot (99.85 wt% purity) and Si (99.02 wt% purity) were used as starting materials to prepare the designed Mg-6.2wt%Si alloy. Based on the previous work, 1,8) 5 wt% KBF 4 that can fully modify Mg-6.2Si alloy was adopted. Details of the fabrication process of Mg-high Si alloys unmodified and modified with KBF 4 were described in elsewhere. 1,8) The unmodified and KBF 4 -modified Mg-6.2Si melts were manually stirred for about 2 min using a stainless steel impeller, held at ϳ800°C for 3 min, and then poured into a copper mold with the holes of f20 mmϫ100 mm and f6 mmϫ100 mm preheated at ϳ120°C, respectively.The partial remelting experiment was performed in an electric resistance furnace under a protective atmosphere of flowing gas of SF 6 (0.6 vol%) and CO 2 (Bal.). When the furnace was heated to 500°C, the circular column samples (f20 mmϫ10 mm and f6 mmϫ10 mm) were placed in the furnace. Then the furnace was heated to the predetermined temperatures (620, 640 or 660°C) with a heating rate of ϳ8°C/min, and isothermally held at that temperatures for 20 min. The temperature was monitored by the use of a thermocouple placed at the centre of the sample with an accuracy of Ϯ1°C. To preserve the morphology and amount of the unmelted fractions which existed at high temperatures, the samples were withdrawn and then quenched in cold water i...

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“…Other than expensive methods of rapid solidification and mechanical alloying, [4] high cooling rates and impurity modifications are well-known techniques that have been used so far. Zhang et al [5] used a wedge copper mold with a range of cooling rates, and Ourfali et al [6] applied Bridgman solidification with different withdrawal velocities. Both methods were found to be effective in refining the coarse Mg 2 Si structure and producing a final dendritic structure.…”

Section: Introductionmentioning

confidence: 99%

Modification of Cast Al-Mg2Si Metal Matrix Composite by Li

Hadian

Emamy

Campbell

2009

Metall Mater Trans B

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The effects of both Li modification and cooling rate on the microstructure and tensile properties of an in-situ prepared Al-15 pct Mg 2 Si composite were investigated. Adding 0.3 pct Li reduced the average size of Mg 2 Si primary particles from~30 to~6 lm. The effect of cooling rate was investigated by the use of a mold with different section thicknesses from 3 to 9 mm. The results show a refinement of primary particle size as a result of both Li additions and cooling rate increases, and their effects are additive. Similarly, both effects increased ultimate tensile stress (UTS) and elongation values. The thin sections show somewhat unexpectedly low and scattered tensile results attributed to the casting defects observed in fracture surfaces. The Li-modified alloy displays serrated yielding behavior that is not fully explained here. The refinement by Li and enhanced cooling rate is explained in terms of an analogy with the effect of Sr and cooling rate in Al-Si alloys, and is ultimately attributed to the effect of the alkali and alkaline earth metals deactivating oxide double films (bifilms) suspended in Al melts as favored substrates for intermetallics.

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Cited by 65 publications

References 7 publications

Modification of Mg2Si in Mg–Si alloys with K2TiF6, KBF4 and KBF4 + K2TiF6

Modification of Mg2Si in Mg–Si alloys with K2TiF6, KBF4 and KBF4 + K2TiF6

Influences of Morphology and Size of Mg2Si on Microstructural Evolution of Mg–6.2Si Alloys during Partial Remelting

Modification of Cast Al-Mg2Si Metal Matrix Composite by Li

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