Microstructure,texture,mechanical properties and corrosion behavior of the extruded Mg-4Zn alloy,as a biodegradable material,were investigated.A refined microstructure caused by dynamic recrystallization(DRX),and a ge...Microstructure,texture,mechanical properties and corrosion behavior of the extruded Mg-4Zn alloy,as a biodegradable material,were investigated.A refined microstructure caused by dynamic recrystallization(DRX),and a general fiber texture were achieved after extrusion.Mechanical properties along different directions of the extruded samples were investigated using shear punch test(SPT).The shear yield stress(SYS)of 113.8 MPa obtained in the transverse direction(TD)was higher than the 106 MPa achieved for the extruded direction(ED)and 45˚samples.This was attributed to the higher amounts of twins and also lower Schmid factor(SF)in the TD.On the other hand,encouraged activation of the basal slip system in the 45˚samples resulted in improved room temperature formability,as indicated by the normalized displacement in the SPT diagram.Electron back scattered diffraction(EBSD)analysis of the surfaces corroded in the phosphate buffered saline(PBS)solution,showed that despite having similar grain sizes and second phase particles shape and volume fractions,surfaces containing grains near(0001)orientations and extension twins<10¯12>(TD and 45˚samples)have lower corrosion rates,as compared to the ED specimens.展开更多
Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample afte...Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample after applying sheet extrusion(size:68μm)changed to fine grains of 6.0 and 5.2μm after 3 and 5 passes of DECLE and following extrusion.The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test(SPT)results.SPT was carried out in the temperature range of 200−300℃ and strain rate range of 0.003−0.33 s^(–1).The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions,which indicated that dislocation creep,controlled by dislocation climb and solute drag mechanism,acted as the main hot deformation mechanism.It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction,and the relationship of which was anticipated using a 3D surface curve.Moreover,the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.展开更多
文摘Microstructure,texture,mechanical properties and corrosion behavior of the extruded Mg-4Zn alloy,as a biodegradable material,were investigated.A refined microstructure caused by dynamic recrystallization(DRX),and a general fiber texture were achieved after extrusion.Mechanical properties along different directions of the extruded samples were investigated using shear punch test(SPT).The shear yield stress(SYS)of 113.8 MPa obtained in the transverse direction(TD)was higher than the 106 MPa achieved for the extruded direction(ED)and 45˚samples.This was attributed to the higher amounts of twins and also lower Schmid factor(SF)in the TD.On the other hand,encouraged activation of the basal slip system in the 45˚samples resulted in improved room temperature formability,as indicated by the normalized displacement in the SPT diagram.Electron back scattered diffraction(EBSD)analysis of the surfaces corroded in the phosphate buffered saline(PBS)solution,showed that despite having similar grain sizes and second phase particles shape and volume fractions,surfaces containing grains near(0001)orientations and extension twins<10¯12>(TD and 45˚samples)have lower corrosion rates,as compared to the ED specimens.
文摘Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample after applying sheet extrusion(size:68μm)changed to fine grains of 6.0 and 5.2μm after 3 and 5 passes of DECLE and following extrusion.The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test(SPT)results.SPT was carried out in the temperature range of 200−300℃ and strain rate range of 0.003−0.33 s^(–1).The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions,which indicated that dislocation creep,controlled by dislocation climb and solute drag mechanism,acted as the main hot deformation mechanism.It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction,and the relationship of which was anticipated using a 3D surface curve.Moreover,the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.
