Modification of Mg2Si morphology in Mg–Si alloys with Bi

Guo, Erjun; Ma, Bing; Wang, L.P.

doi:10.1016/j.jmatprotec.2007.12.038

Cited by 84 publications

(41 citation statements)

References 21 publications

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“…[15] In another work, Bi has been added to Mg-Si alloys to modify the morphology of Mg 2 Si particles. [16] It was found that the optimal Bi content of 0.5 wt pct significantly decreased the size of Mg 2 Si particles and changed its morphology from coarse dendritic shape to polyhedral shape.…”

Section: Introductionmentioning

confidence: 95%

Microstructure and Impression Creep Characteristics of Cast Mg-5Sn-xBi Magnesium Alloys

Keyvani

Mahmudi

Nayyeri

2010

Metall Mater Trans A

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The microstructure and creep behavior of a cast Mg-5Sn alloy with 1, 2, and 3 wt pct Bi additions were studied by impression tests in the temperature range 423 K to 523 K (150°C to 250°C) under punching stresses in the range 125 to 475 MPa for dwell times up to 3600 seconds. The alloy containing 3 wt pct Bi showed the lowest creep rates and, thus, the highest creep resistance among all materials tested. This is attributed to the favorable formation of the more thermally stable Mg 3 Bi 2 intermetallic compound, the reduction in the volume fraction of the less stable Mg 2 Sn phase, and the dissolution of Bi in the remaining Mg 2 Sn particles. These particles strengthen both the matrix and grain boundaries during creep deformation of the investigated system. The creep behavior of the Mg-5Sn alloy can be divided into the low-and high-stress regimes, with the respective average stress exponents of 5.5 and 10.5 and activation energies of 98.3 and 163.5 kJ mol À1 . This is in contrast to the creep behavior of the Bi-containing alloys, which can be expressed by a single linear relationship over the whole stress and temperature ranges studied, yielding stress exponents in the range 7 to 8 and activation energies of 101.0 to 107.0 kJ mol À1 . Based on the obtained stress exponents and activation energies, it is proposed that the dominant creep mechanism in Mg-5Sn is pipe-diffusion controlled dislocation viscous glide the low-stress regime and dislocation climb creep with back stress in the high-stress regime. For the Mg-5Sn-xBi alloys, however, the controlling creep mechanism is dislocation climb with an additional particle strengthening effect, which is characterized by the higher stress exponent of 7 to 8.

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Section: Introductionmentioning

confidence: 95%

Microstructure and Impression Creep Characteristics of Cast Mg-5Sn-xBi Magnesium Alloys

Keyvani

Mahmudi

Nayyeri

2010

Metall Mater Trans A

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“…Mg-Si alloys can be divided into two groups: hypoeutectic (below 1.45 at.% Si) and hypereutectic (above 1.45 at.% Si). Unfortunately, the as-cast hypereutectic alloys have a low mechanical properties due to the presence of primary Mg2Si compound which forms the large particles in the matrix [9][10][11][12][13][14]. In order to improve the mechanical properties the modified treatment can be used, however, the improvement of mechanical properties after modification is not impressive.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Aluminum on the Microstructure and Hardness of Mg-5Si-7Sn Alloy

Rzychoń¹,

Dybowski²

2016

Archives of Metallurgy and Materials

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Magnesium alloys due the low density and good mechanical properties are mainly used in the automotive and aerospace industry. In recent years, magnesium alloys are extensively developed for use in high temperatures (above 120°C). Among these alloys, magnesium alloys containing tin and silicon have large possibilities of application due to the formation of thermally stable intermetallic Mg2Sn and Mg2Si. In this paper the influence of aluminum and heat treatment on the on the microstructure and hardness of Mg-7Sn-5Si alloy is reported. It was found that the microstructure of Mg-7Sn-5Si alloy consist of α-Mg solid solution, Mg2Sn and Mg2Si compounds. Addition of 2 wt% of Al to Mg-7Sn-5Si alloy causes the formation of Al2Sn phase. Moreover, Al dissolves in the α-Mg solid solution. The solution heat-treatment of tested alloys at 500°C for 24 h causes the dissolve the Mg2Sn phase in the α-Mg matrix and spheroidization of Mg2Si compound. The Mg2Si primary crystals are stable at solution temperature. After ageing treatment the precipitation process of equilibrium Mg2Sn phase was found in both alloys. The addition of aluminum has a positive effect on the hardness of Mg-7Sn-5Si alloy. In case of Mg-5Si-7Sn-2Al alloy the highest hardness was obtained for sample aged for 148 h at 250°C (88 HV2), while in case of Al-free alloy the highest hardness is 70 HV for material aged for 148 h at 250°C.

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“…However, compared with the above-mentioned techniques, modification treatment is a more cost-effective processing technique and available for generally commercial application. Much work has been focused on the modification effects of rare earth [8], KBF 4 [9,10], Sr [11], Sb [12,13], Bi [14], Ba [15], Ca and P [16] on the primary and eutectic Mg 2 Si in magnesium alloys. However, it was reported that certain internal defects exist.…”

Section: Introductionmentioning

confidence: 99%

“…For example, although KBF 4 has a good effect on the modification of Mg 2 Si phase in Mg-5Si alloys, a large quantity of smoke and sputter [9,10] is produced, which is harmful to the surrounding environment. Besides, Bi [14] and Ba [15] can modify and refine the primary Mg 2 Si, but the Mg 2 Si phase becomes coarse again when the adding amount exceeds a limit.…”

Section: Introductionmentioning

confidence: 99%