Influence of Fe on the Formation of Nucleation in Carbon-Inoculated Mg-3%Al Alloy

Abstract

The Mg-3% Al melt was treated by carbon inoculation and Fe addition. The influence of Fe on the formation of nucleation was investigated. That Fe inhibited the grain refinement of the carbon-inoculated Mg-3%Al alloy or not was closely associated with the operating sequence of carbon inoculation and Fe addition. Under the condition of Fe addition firstly and then carbon inoculation, the Al4C3particles and the particles with duplex phase structure of Al4C3coated on Al-C-Fe or Al-Fe could be observed. Both kinds of particles should act as nucleating substrates for a-Mg grains, resulting in no obvious effect of Fe on refining efficiency of carbon inoculation. Under the contrary condition, the potency of Al4C3nucleating substrates was poisoned by transforming Al4C3into Al-C-Fe-rich intermetallic particles, resulting in grain-coarsening.

Inclusion removal and grain refinement of magnesium alloy castings

“…The nucleating particles for cases where Ca, Fe and C were all present were duplex phases with Al-C-O-Fe cores and Al-C-O coatings suspected to be Al 4 C 3 on Al-Fe or Al-Fe-C phases [194]. In previous research, the duplex phase formed only if Fe was added before C inoculation [241].…”

“…who observed that Al-C-O particles acted as nucleants and that Fe and/or Mn additions poisoned these nucleants to less effective 69% reduction) for the alloys refined by Fe only (by Al-Fe intermetallics[241]) or Fe then C respectively[241,242]. If the alloy was refined by C first then Fe the grain size would increase from 183 (70% reduction) to 582 μm (5% reduction) for the alloys refined by C only or C then Fe respectively[241,242]. The C refined alloy had Al-C-O particles while the Fe then C refined alloy had both Al-C-O and Al-C-O-Fe particles.…”