Grain refining mechanism in Mg–9Gd–4Y alloys by zirconium

Abstract

The effect of different zirconium contents on the grain size of Mg-9Gd-4Y alloys and the grain refinement mechanism of zirconium have been studied. The results reveal that zirconium can refine the grains of the alloys to a large extent, and the grains become finer with an increase of zirconium content. Microstructural analysis shows that there is at least one zirconium rich core in almost each grain in alloys with a high zirconium content, whereas the characteristic zirconium rich cores are not found in the alloy with a low zirconium content. It is suggested that the grain refinement mechanism of zirconium in the low zirconium alloy is different from that in the high zirconium alloys: the zirconium works mainly by restricting grain growth in the low zirconium alloy, and by generating nucleants in the high zirconium alloys.

Fatigue of rare‐earth containing magnesium alloys: a review

“…The Gd‐containing intermetallic compounds in Mg‐8Gd‐xZn‐0.4Zr alloys were broken during hot extrusion and then dispersed along the direction of hot extrusion. During hot extrusion, recrystallized grains formed on the initially grain boundaries suggest that the accumulation of dislocations at grain boundaries stimulates the DRX process, and this also reflects the role of added RE elements . A similar type of extruded microstructures is also reported in Refs.…”

“…[22][23][24][25]32 This was due to the role of added RE elements and zirconium, where Zr mainly restricted the grain growth. 63 A similar role of grain refinement by RE elements, for example, gadolinium, 51 yttrium, 64 cerium 65 and neodymium, 42 has been reported as well. In addition, according to the study by He et al, 47 as-cast Mg-10Gd-2Y-0.5Zr alloy contains three different phases: α-Mg solid solution matrix phase with supersaturated Gd+Y elements, (Gd+Y)-rich eutectic compound, which had a higher Gd+Y content than the matrix, and intracrystalline Zr-rich cores.…”

Effect of Zr, Mn and Sc additions on the grain size of Mg–Gd alloy

“…From the Mg-Zr phase diagram, these metallic particles in the cores appear to be ␣-Zr. The characteristic Zr rich cores have also been observed in Mg-Zr and Mg-Gd-Y-Zr alloys [15][16][17][18]. It is these Zr rich cores that play an important role on refining grains by generating nucleants during the solidification.…”

Effect of corrosion attack on the fatigue behavior of an as-cast Mg–7%Gd–5%Y–1%Nd–0.5%Zr alloy

“…3(e)), which is close to that of Mg 5 Gd (f.c.c., a = 2.23 nm [31]). Previous work demonstrated that Zr-rich particles mainly existed in grain interior and formed from the peritectic reaction during solidification and could act as nuclei for the grain refinement of Mg alloys [32][33][34][35]. In the research about the effect of Zr on grain refinement for an as-cast Mg-Gd-Y-Zr alloy, Sun et al reported that no Zr-containing phases could be formed [32].…”