Thermal stability and microstructure development of cast and powder metallurgy produced Mg-Y-Zn alloy during heat treatment  

作　　者：Tomas Kekule Bohumil Smola Martin Vlach Hana Kudrnova Veronika Kodetova Ivana Stulikova 

机构地区：[1]Charles University in Prague,Faculty of Mathematics and Physics,Ke Karlovu 3,Praha 212116,Czech Republic

出　　处：《Journal of Magnesium and Alloys》2017年第2期173-180,共8页镁合金学报（英文）

基　　金：the Czech Science Foundation(GACR),project No.16-12828S is also gratefully acknowledged.

摘　　要：Response to isochronal annealing up to 440 ℃ of squeeze cast Mg–Y–Zn alloy and of the same alloy prepared by powder metallurgy(PM)and extruded at 280 ℃ was studied by resistivity and microhardness measurement,differential scanning calorimetry(DSC)and microstructure investigation.Electrical resistivity was measured at 77 K and microhardness was measured at room temperature after each annealing step.DSC measurement was performed at various heating rates.Transmission and scanning electron microscopy and optical microscopy revealed ribbons of long-period ordered structure(LPSO)18R and planar defects within grain boundaries.Relatively high density of planar defects was found in grain interiors of the cast alloy with the grain size approximately 50μm.Well pronounced subgrains were observed in the PM prepared alloy.Secondary phase particles decorate grain boundaries in this alloy.Three precipitation processes were detected in the cast alloy during repeated isochronal annealing up to 440 ℃,whereas only one significant process was revealed in the PM alloy.These processes were identified as embedding of stacking faults by solutes,development and rearrangement(18R→14H)of LPSO phase and development of grain boundary particles.A coarsening of grain boundary particles rich in Y and Zn only proceeds in the PM alloy.Activation energies of the precipitation processes were determined.Microhardness exhibits good thermal stability against annealing up to 360 ℃ in the PM alloy.

关 键 词：Mg-Y-Zn alloys Powder metallurgy MICROHARDNESS Microstructure development Electrical resistivity 

分 类 号：TG1[金属学及工艺—金属学]