The Evolution Of Microstructure And Properties In Casting And Wrought Mg-Gd-Zn(-Zr) Alloys Containing LPSO Struture

Magnesium alloy develops rapidly as green engineering materials in recent years and has the advantages of short process,low consumption,high quality,and recyclable reuse.Mg-Gd alloy is becoming one of the most promising alloy systems due to its excellent characteristics of aging strengthening,and a long period ordered structure which is formed after the addition of Zn provides a new way to strengthen the alloyThis paper studies on the Mg-Gd-Zn(-Zr)alloy.The Mg-14Gd-2Zn(GZ142,wt.%)and Mg-14Gd-2Zn-0.3Zr(GZ142K,wt.%)were produced by gravity casting and semi continuous casting.And the same time,this paper studies on the evolution of microstructure and properties about casting Mg-Gd-Zn(-Zr)with LPSO structure through the different test ways,such as ICP,OM,XRD,SEM,TEM,DSC,nano indentation,tensile and so on.Then the microstructure and mechanical properties of the wrought Mg-Gd-Zn(-Zr)alloy were studied through differential temperature extrusion and cold rolling.Focus on the formation and evolution of the LPSO structure and the effect on the properties of the alloy.The 14H-LPSO structure and 18R-LPSO structure were distributed in the gravity casting Mg-Gd-Zn alloy.In the as-cast Mg-Gd-Zn alloy,the former exists in the ?-Mg grain and the latter exists at the grain boundary.This is the first time to find the 18R-LPSO structure in the metal mould gravity casting Mg-Gd-Zn alloy.After the solid solution treatment,exceptthe 14H-LPSO in the ?-Mg grain,the 18R-LPSO structure at the grain boundary has been turned into the 14H-LPSO structure.After the differential temperature extrusion,the recovery recrystallization,the grain refinement and the two-peak structure would be happened in the GZ142 and GZ142K alloys,and the LPSO structure would be bending.The degree of recrystallization and the grain size would be increased,and the microstructure of two-peak and the LPSO structure would be decreased as the die mold temperature increase from 320? to 420?.The mechanical properties of low temperature(mold temperature 320?)extrusion alloy at room temperature are better.The yield strength,tensile strength and elongation of the peak-aged GZ142 K with the rolling deformation 4.4% and mold temperature 320? could reach397 MPa,467MPa and 1.8%.