A novel T-type specimen enabled the separation of the thermal and athermal contributions of electropulsing treatment(EPT)in pretwinned AZ31 Mg alloy.The combination of T-type geometry and carefully selected EPT condit...A novel T-type specimen enabled the separation of the thermal and athermal contributions of electropulsing treatment(EPT)in pretwinned AZ31 Mg alloy.The combination of T-type geometry and carefully selected EPT conditions equalized the thermal contributions at two distinct locations(J70-C and J77-D)in a thermally stable regime,which isolated the athermal effect in J70-C.The results were verified using finite element analysis.Although the athermal EPT contribution did not alter the fundamental microstructural evolution mechanisms,the evolution rate increased significantly.As a result,the J70-C region exhibited faster grain growth,annihilation of twin boundaries,reduction of low-angle grain boundaries,dislocation annihilation,and static recrystallization compared to its counterpart,as further supported by the microhardness trends.These results were interpreted in light of the additional driving force by the athermal EPT contribution,which accelerated the strain-induced boundary migrations beyond Joule heating alone.The proposed T-type specimen methodology offers a robust framework for decoupling the thermal and athermal effects in macroscale EPT processes.展开更多
Alloying with Gd and Ag can significantly enhance the comprehensive properties of magnesium alloys,and accurate phase equilibria are a necessity for advanced alloy design.However,literature review reveals limited info...Alloying with Gd and Ag can significantly enhance the comprehensive properties of magnesium alloys,and accurate phase equilibria are a necessity for advanced alloy design.However,literature review reveals limited information on the phase equilibria in the ternary Mg-Gd-Ag system.Thus,in this paper,the phase equilibria of the ternary Mg-Gd-Ag system in the region of 0-50 at.%Gd at 450℃and 500℃were investigated by combining the electron probe microanalysis and X-ray diffraction of totally 66 equilibrated alloys,with two isothermal sections at 450℃and 500℃established accordingly;and relatively high solid solubility of Ag in GdMg_(3)was characterized.Moreover,seven ternary compounds(denoted asτ_(1)toτ_(7))were found,and their crystal structures were refined by using Rietveld method.Theτ_(1)was identical to the previously reported X phase with a diamond-cubic structure,while the remaining six ternary compounds(τ_(2)toτ_(7))were newly found.The seven ternary compounds(τ_(1)toτ_(7))are among the space groups of Fd3m(τ_(1)),P4/nmm(τ_(2)),P63mc(τ_(3)),P63mc(τ_(4)),Pmn2_(1)(τ_(5)),P62m(τ_(6))and Pc(τ_(7)).Their homogeneity ranges and lattice parameters were carefully determined.The solubilities of the third elements in the binary compounds of the three subsystems were also well measured.It is anticipated that the presently obtained phase equilibria as well as the crystal structures of ternary compounds in the Mg-Gd-Ag system would serve as a foundation for developing thermodynamic database and alloy design in the near future.展开更多
基金funded by the Defense Acquisition Program Administration(DAPA)(Grant No.KRIT-CT-23-059)supported by the‘Human Resources Program in Energy Technology’of the Korea Institute of Energy Technology Evaluation and Planning(KETEP),which was funded by the Ministry of Trade,Industry,and Energy(MOTIE)(Grant No.RS-2024-00398425).
文摘A novel T-type specimen enabled the separation of the thermal and athermal contributions of electropulsing treatment(EPT)in pretwinned AZ31 Mg alloy.The combination of T-type geometry and carefully selected EPT conditions equalized the thermal contributions at two distinct locations(J70-C and J77-D)in a thermally stable regime,which isolated the athermal effect in J70-C.The results were verified using finite element analysis.Although the athermal EPT contribution did not alter the fundamental microstructural evolution mechanisms,the evolution rate increased significantly.As a result,the J70-C region exhibited faster grain growth,annihilation of twin boundaries,reduction of low-angle grain boundaries,dislocation annihilation,and static recrystallization compared to its counterpart,as further supported by the microhardness trends.These results were interpreted in light of the additional driving force by the athermal EPT contribution,which accelerated the strain-induced boundary migrations beyond Joule heating alone.The proposed T-type specimen methodology offers a robust framework for decoupling the thermal and athermal effects in macroscale EPT processes.
基金support from the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(No.2021JJ10062)is acknowledged.
文摘Alloying with Gd and Ag can significantly enhance the comprehensive properties of magnesium alloys,and accurate phase equilibria are a necessity for advanced alloy design.However,literature review reveals limited information on the phase equilibria in the ternary Mg-Gd-Ag system.Thus,in this paper,the phase equilibria of the ternary Mg-Gd-Ag system in the region of 0-50 at.%Gd at 450℃and 500℃were investigated by combining the electron probe microanalysis and X-ray diffraction of totally 66 equilibrated alloys,with two isothermal sections at 450℃and 500℃established accordingly;and relatively high solid solubility of Ag in GdMg_(3)was characterized.Moreover,seven ternary compounds(denoted asτ_(1)toτ_(7))were found,and their crystal structures were refined by using Rietveld method.Theτ_(1)was identical to the previously reported X phase with a diamond-cubic structure,while the remaining six ternary compounds(τ_(2)toτ_(7))were newly found.The seven ternary compounds(τ_(1)toτ_(7))are among the space groups of Fd3m(τ_(1)),P4/nmm(τ_(2)),P63mc(τ_(3)),P63mc(τ_(4)),Pmn2_(1)(τ_(5)),P62m(τ_(6))and Pc(τ_(7)).Their homogeneity ranges and lattice parameters were carefully determined.The solubilities of the third elements in the binary compounds of the three subsystems were also well measured.It is anticipated that the presently obtained phase equilibria as well as the crystal structures of ternary compounds in the Mg-Gd-Ag system would serve as a foundation for developing thermodynamic database and alloy design in the near future.
