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| 1 | Influence of Bi addition on dynamic recrystallization and precipitation behaviors during hot extrusion of pure Mg显示文摘Low material cost and high extrudability for ensuring price competitiveness with Al alloys,as well as excellent mechanical properties,are essential for expanding the application range of Mg extrudates.Bi is a promising alloying element for developing extruded Mg alloys that satisfy such requirements.Bi is inexpensive,exhibits a high solubility limit,and forms a thermally stable Mg3Bi2 phase,which improves the commercial viability and enables the high-speed extrusion of Mg–Bi alloys.In this study,the effects of Bi addition on the dynamic recrystallization(DRX)and dynamic precipitation behaviors during hot extrusion of a pure Mg and the resultant microstructure and mechanical properties of the extruded materials were investigated.The addition of 6 wt%and 9 wt%Bi to a pure Mg yielded numerous fine Mg3Bi2 precipitates during the early stage of hot extrusion.Consequently,the area fraction of dynamic recrystallized(DRXed)grains decreased because of DRX-behavior suppression by the Zener pinning effect.However,the DRXed grain size was substantially reduced through the grain-boundary pinning effect.The size and number of undissolved Mg3Bi2 particles in the homogenized billets increased when the Bi content was increased,which resulted in increased DRX fractions owing to the enhanced levels of particle stimulated nucleation.Bi addition yielded considerable strength improvement of the extruded pure Mg.However,the extruded Mg–Bi binary materials were less ductile than the extruded pure Mg material.This lower ductility resulted from the cracking at twins formed in the coarse unDRXed grains of the Mg-6Bi material and the cracking at large undissolved Mg3Bi2 particles in the Mg-9Bi material. | Jongbin Go Jong Un Lee Hui Yu Sung Hyuk Park | 2020 | Journal of Materials Science & Technology2020，44，9： | 3 |
| 2 | Elucidating the evolution of long-period stacking ordered phase and its effect on deformation behavior in the as-cast Mg-6Gd-1Zn-0.6Zr alloy显示文摘Herein,the evolution of long-period stacking ordered(LPSO)phases in the as-cast Mg-6Gd-1Zn-0.6Zr(wt.%)alloy are investigated via transmission electron microscopy(TEM)and atom probe tomography(APT).The TEM results reveal that two types of LPSO phase(a bulky interdendritic phase and a plate-like matrix LPSO phase)are formed in the as-cast sample.Most of the LPSO phases are confirmed to be of the 14H type,with a smaller proportion being of the 18R LPSO.Further,the APT results reveal that the composition of the interdendritic LPSO phase is closer to that of the ideal 14H phase compared to the matrix LPSO phase,and both the interdendritic and matrix LPSO phases exhibit a Gd/Zn ratio of 2.5,thereby indicating a deficient Zn content compared to the ideal 14H phase(i.e.,1.3).In addition,the influence of the LPSO phases on the deformation behavior is investigated at different compressive plastic strains using electron backscatter diffraction(EBSD)analysis to reveal twinning and slip behavior during deformation.The results indicate that the LPSO phase induces additional work hardening in the late stage of deformation via the suppression of{1011}compressive twinning and the activation of non-basal slip systems. | Sangwon Lee Yejun Park Jongbin Go Young Mok Kim Seok Su Sohn Jiehua Li Pyuck-Pa Choi | 2023 | Journal of Magnesium and Alloys2023，11，8： | 0 |
| 3 | Comparative study of extrudability, microstructure, and mechanical properties of AZ80 and BA53 alloys显示文摘The extrudability,microstructural characteristics,and tensile properties of the Mg–5Bi–3Al(BA53)alloy are investigated herein by comparing them with those of a commercial Mg–8Al–0.5 Zn(AZ80)alloy.When AZ80 is extruded at 400℃,severe hot cracking occurs at exit speeds of 4.5 m/min or more.In contrast,BA53 is successfully extruded without any surface cracking at 400℃ and at high exit speeds of 21–40 m/min.When extruded at 3 m/min(AZ80–3)and 40 m/min(BA53–40),both AZ80 and BA53 exhibited completely recrystallized microstructures with a<10–10>basal texture.However,BA53–40 has a coarser grain structure owing to grain growth promoted by the high temperature in the deformation zone.AZ80–3 contains a continuous network of Mg_(17)Al_(12) particles along the grain boundaries,which form via static precipitation during natural air-cooling after the material exits the extrusion die.BA53–40 contains coarse Mg_(3)Bi_(2) particles aligned parallel to the extrusion direction along with numerous uniformly distributed fine Mg_(3)Bi_(2) particles.AZ80–3 has higher tensile strength than BA53–40 because the relatively finer grains and larger number of solute atoms in AZ80–3 result in stronger grain-boundary and solid-solution hardening effects,respectively.Although BA53 is extruded at a high temperature and extrusion speed of 400℃ and 40 m/min,respectively,the extruded material has a high tensile yield strength of 188 MPa.This can be primarily attributed to the large particle hardening effect resulting from the numerous fine Mg_(3)Bi_(2) particles. | Sang-Cheol Jin Jae Won Cha Jongbin Go Jun Ho Bae Sung Hyuk Park | 2023 | Journal of Magnesium and Alloys2023，11，1： | 0 |
| 4 | Effects of Sn addition on the microstructure and mechanical properties of extruded Mg-Bi binary alloy显示文摘We investigated the effects of Sn addition on the microstructural characteristics and mechanical properties of an extruded Mg-Bi binary alloy by comparing Mg-5 Bi(B5)and Mg-5 Bi-4 Sn(BT54).Both the extruded alloys exhibit a partially recrystallized grain structure with a strong extrusion fiber texture and numerous Mg3Bi2 precipitates.However,the addition of Sn significantly decreases the average grain size of the extruded alloy from 123.9 to 75.2μm.The Sn solute atoms inhibit the activity of dislocation slip,which reduces the internal strain energy accumulated in the dynamically recrystallized(DRXed)grains during extrusion.Consequently,this reduced strain energy leads to the decrease in the DRXed grain size owing to weakened grain growth during natural air-cooling.The extruded BT54 alloy exhibits higher tensile strength and ductility than the extruded B5 alloy.The improvement in the strength by the Sn addition is attributed to the combined effects of grain refinement,Sn solute atoms,and increased dislocation density.The formation of{10-11}and{10-11}-{10-12}twins during tension is suppressed by the grain refinement,thereby improving the tensile elongation considerably. | Sang-Cheol Jin Jong Un Lee Jongbin Go Hui Yu Sung Hyuk Park | 2022 | Journal of Magnesium and Alloys2022，10，3： | 0 |
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