Inoculant Fading-Resistance of Fe-Bearing Mg–3%Al Alloys Refined by Carbon Combining with Calcium Addition

Abstract

Mg3%Al alloys containing different trace Fe contents were treated by carbon combining with Ca inoculation. The holding time after being inoculation was adjusted from 5 to 80 min. The effect of holding time on grain refinement and the structures of nucleating particles were systematically investigated. Significant grain refinement is obtained for the Mg3%Al alloys containing trace Fe refined by carbon combining with Ca inoculation. The grain size keep stable with prolonging the holding time and exhibit significant fading-resistance. The duplex-phase particles of AlFe coated with AlC-rich phase could be easily observed and they should actually act as potent nuclei for Mg grains. The Ca content in the AlC-rich shell is obviously higher than that in the Mg matrix. The segregation of Ca on the surfaces of different phases contributes to the formation of duplex-phase particles and keeps the duplex phase structure particles stable. Consequently, no inoculant-fading of carbon-inoculation occurred due to the high stability of the duplex phase structure particles.

Revealing the Nuclei Formation in Carbon-Inoculated Mg-3%Al Alloys Containing Trace Fe

“…These results indicate that the trend of forming stable duplex-phase particles becomes more and more obvious during the carbon inoculation process. This result is also confirmed by our previous research, which showed that the duplex phase particles kept stable when prolonging the holding time to 80 min and exhibit significant fading resistance [6].…”

“…To exactly control the Al content in the Mg–Al melt, the amounts of Al in the pellets and the Al-15%Fe master alloy were carefully taken into consideration. The melting process used in this study is similar to that in our previous research [6]. The added contents of Fe, carbon, and Ca were 0.05%, 0.2%, and 0.2% (mass ratio, the same below) of the melt, respectively.…”

“…For the past decade, grain refinement has become one of the most important routes to improve the mechanical properties of magnesium alloys [1,2,3]. The main grain refining methods for Al-bearing Mg alloys includes superheating [4], Elfinal processing [5], carbon inoculation [6,7,8], and solute addition [9,10,11,12,13]. Among these techniques, carbon inoculation is attracting widespread interest due to its low cost, low operating temperature, and less fading.…”

“…Numerous experiments have identified the existence of duplex-phase structure particle in the Mg–Al melt [26,27,28]. In a recent study conducted by Du et al, it was shown that Al–C-rich phases were coated on Al–Fe or Al–C–Fe-rich phases and that these duplex-phase particles could be potent substrates for α-Mg grains [6,26]. Similar to Fe, Mn is another impurity element that can influence grain refining efficiency.…”

“…For example, two kinds of duplex-phase particles of Al 4 C 3 coated on Al 8 Mn 5 and Al 0.89 Mn 1.11 were found in AZ31 and AZ63 alloys refined by carbon-inoculation, respectively [28]. In addition, alkaline-earth elements, such Ca and Sr, can effectively promote the formation of duplex-phase particles [6,26]. Furthermore, it has been proven that further grain refining efficiency could be obtained for the Mg–Al alloys modified by combining the addition of Ca or Sr with carbon inoculation due to the synergistic action [25].…”