Grain refining mechanisms in Mg–Al alloys with Al4C3 microparticles

Microstructural refinement and tensile properties enhancement of Mg–3Al alloy using charcoal additions

“…It is proposed that initially Al 4 C 3 particles form in the melt from the reaction between C and Al atoms, which in turn facilitates the formation of the Al 8 Mn 5 phase and subsequently the surface of polygonal Al 8 Mn 5 phase, nucleates ␣-Mg grain. Similar observation has been made by Nimityongskul et al [19], when Al 4 C 3 particles have been introduced in to the AM60B alloy. It is clearly understood from the literature, that the presence of Mn enhances the efficiency of Al 4 C 3 for grain refinement in Mg-Al alloys containing ≥6%Al and at the same time, Al 4 C 3 itself is able to nucleate ␣-Mg grains in Mn free Mg-3Al alloy system [14,19].…”

“…This hypothesis has been further supported by Guang et al [15]; they have demonstrated that, owing to the presence of fine Al 4 C 3 particles, considerable grain refinement is obtained in AZ31 Mg alloy when carbon addition has been carried out using Al-1C master alloy. However, some authors have proposed a duplex nucleation theory [12,18,19]. Ding and Liu [18] have demonstrated that the addition of Ni-C alloy in to Mg-3Al alloy has lead to the formation of Al 4 C 3 nuclei initially and subsequently they have reacted with Al-Ni phase to form Al-Ni-C ternary compounds.…”

Investigation of the microstructure and the influence of iron on the formation of Al8Mn5 particles in twin roll cast AZ31 magnesium alloy

“…Cao and co-workers [10,13] reported the formation of Al-rich, Fe-rich and Mn-rich particles at the centres of the grains in Mg-Al based magnesium alloys. A duplex nucleation mechanism has also been reported that includes inoculation by Al 4 C 3 particles which act as active nucleation sites for the formation of Al 8 Mn 5 particles in the first stage; the Al 8 Mn 5 particles further act as effective nucleation sites for the a-Mg grains in Mg-Al-Zn and Mg-Al-Mn magnesium alloys [14,15]. Kim et al reported on the observation of Al-Mn dispersoid particles in the interdendritic regions, with irregular shapes and sizes ranging from 100 to 200 nm, in as-strip-cast ZMA6111 magnesium alloy [16].…”

Microstructure Refinement After the Addition of Titanium Particles in AZ31 Magnesium Alloy Resistance Spot Welds

“…[20,21] Furthermore, Kim et al [22] proposed a theory of duplex nucleation, according to which, a polygonal Al 8 Mn 5 first nucleates on the surface of Al 4 C 3 and then a-Mg nucleates on the surface of Al 8 Mn 5 in Mn-containing Mg-Al alloy systems. Nimityongskul et al [23] provided direct experimental evidence of this duplex nucleation model in AM60B castings.…”

“…The objective of this work is to study the effect of extraneous Ti addition as an inoculant on the microstructure refinement and mechanical property improvement of AZ31 alloy welds that did not contain coarse Al 8 Mn 5 second phase particles. [1] Although the grain refinement by inoculants with varying potency in Mg-Al alloys has been studied by several investigators, [8][9][10][11][12][13][14][15][16][21][22][23]26] the mechanism of grain refinement is still unclear. The further objective of this article is to analyze the relationship between the type and size of inoculants and supercooling, and their effect on the heterogeneous nucleation behavior and microstructure refinement in the fusion zone of AZ31 Mg welds.…”