Abstract
It has long been recognized that grain refinement of Mg-Al alloys is difficult, although various methods have been tried. In the present paper, a novel grain refiner, Al-3.4V-1B master alloy, has been developed to refine the as-cast AZ91 alloy. A comparative study on grain refinement effects of Al-3.4V-1B, Al-5V, and Al-3Ti-1B master alloys was performed under the same solidification conditions. It is shown that Al-3.4V-1B master alloy not only has significant grain refinement ability, but also keeps stable anti-fading capacity with holding time up to 2 h. Based on the analysis of grain refinement, VB2 particles introduced by Al-3.4V-1B master alloy are the heterogeneous nuclei for AZ91 alloy.
Highlights
Mg alloys are known as “green engineering materials for the 21st century”, which have been used in aerospace, automobiles, electronic products due to their low densities, and high specific strengths [1,2,3]
It is most likely that the VB2 particles are the potential effective nucleation sites for AZ91 alloy rather than Al3 V particles due to the fact that the no obvious grain refinement is obtained in AZ91 alloy inoculated by Al-5V master alloy
The grain refinement of AZ91 alloy induced by Al-3.4V-1B master alloy was investigated in the present paper
Summary
Mg alloys are known as “green engineering materials for the 21st century”, which have been used in aerospace, automobiles, electronic products due to their low densities, and high specific strengths [1,2,3]. With the increase in demands for energy conservation and emission reduction, light-weighting materials including Mg alloys will be in continuous demand [4,5]. Grain refinement can simultaneously improve strength and ductility, and can reduce casting defects, such as segregations and porosity. Zirconium has been widely applied to cause grain refinement of magnesium alloys. After adding 0.15 wt.% of zirconium to the melt, a grain size reduction of more than 80% was achieved [7]. The significant grain refinement induced by zirconium does not occur in these magnesium alloys with aluminum, because aluminum and zirconium can readily form stable intermetallic phases, which are ineffective as nucleant particles for magnesium grains [7,8]
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