Effect of Alloy Composition on Microstructure and Strength of Fine Grained Extruded Mg‐Zn‐Y Alloys Containing Quasicrystal Phase

Effect of Solidification Cooling Rate on Microstructure and Mechanical Properties of an Extruded Mg-Zn-Y Alloy

“…The YAS can be related to the composition of the alloy and the extrusion temperature. The YAS becomes lower with a lower concentration of solute [18,19,21] and a lower extrusion temperature [19]. Both conditions result in a lower rate of recrystallization.…”

“…However, since the Mg-3.0Zn-0.5Y alloy was not fully recrystallized after extrusion, this condition is changed [19]. The unrecrystallized regions of the alloy, which contain lattice strain in form of dislocations and subgrain/low angle boundaries, offer resistance to further slip but almost none to twinning [18,19,21]. Since twinning is associated with compression, the compression will become easier and the slope of the Hall-Petch plot in compression lower (extrusions at lower temperates are likely to have larger unrecrystallized regions; in other words, finer grained alloys are associated with larger regions of unrecrystallized grains).…”

“…Very high strength has been reported in alloys containing the LPSO phase after wrought processing [4][5][6]. In the case of alloys containing the i-phase , very high strengths in combination with good ductility and low anisotropy have been reported [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Apart from the dispersion of the i-phase , these alloys are strengthened by Zn solid solution and Mg-Zn binary phase precipitation.…”

“…Very high strengths were shown after powder metallurgy of Mg-Zn-Y alloys in which the grain size was reduced to the sub-micron level [16]. However, it was also shown that micron and sub-micron grain size could be obtained by simple extrusion from alloys cast by chill casting method, resulting in tensile yield stresses (YS) nearing or better than 400 MPa, accompanied by total elongation of over 13% [17][18][19]21]. The supersaturated matrix in these alloys resulted in dynamic precipitation of nano-sized precipitates of Mg-Zn phase during extrusion.…”

“…In this study solidification methods were used for the purpose of obtaining the best mechanical properties after subsequent wrought processing. Since chill casting of the alloy was deemed necessary to achieve these properties after extrusion [17][18][19]21], in the present study chill casting is compared with a conventional steel mold casting and a water-cooled mold casting of a Mg-Zn-Y alloy. The effect of these three casting processes on solidification and extruded microstructure, as well as on mechanical properties are studied.…”