Quantitative Discussion on Superplastic Deformation Mechanisms Mg—4.3 Al—Zn—0.4Mn Alloy
Zhang Min chen Pu quan Zhang Jiren (Harbin Institute of Technology)
Sheet specimens of Mg4.3 3Al-Zn-0.4Mn alloy have beeu elongated in the range rate fram■=3.33×10~(-6)s~(-1) to～1.67×10~(-1)s~(-1),and the strain-rate sensitivity indexes m also measured by means of the sudden change of strain-rate which was suggested by Backofen.The complete curves (log a/log ■and m/log■have been obtained.The contributions of grain boundary sliding (GBS),diffusion creep(DC), dislocation slip(DS) to total elongation were estimated respectively in the regions Ⅰ,Ⅱ and Ⅲ of loga/log ■ curve with the help of the replicas of transmission elect- ran micrograph.The results calculated are as follows: region Ⅰ:r_(GBS)=35%,r_(DC)=37.8%,r_(DS)=19.6%. region Ⅱ:r_(GBS)=58%,r_(DC);28.5%,r_(DS)=12.3%. region Ⅲ:r_(GBS)=19%,r_(DC)=6.3%,r_(DS)=69%. According to these quantitative data,the mutual effects and accommodation. relationships of the three deformation mechanisms during the superplastic deformatien is analyzed.