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RISS 인기검색어
- 검색키워드
- 저자 : Jongbin Go (검색결과 2 건)
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Improvement in Mechanical Properties of Rolled AZ31 Alloy Through Combined Addition of Ca and Gd
Jongbin Go,Jong Un Lee,문병기,Jonghun Yoon,Sung Hyuk Park 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.12
In this study, the effects of the combined addition of Ca and Gd on the microstructure and mechanical properties of rolledMg alloys are investigated by the addition of 0.5 wt% Ca and 0.5 wt% Gd to a commercial AZ31 alloy. The combined additionof Ca and Gd leads to the formation of undissolved second phases such as Al2Caand Al2Gd,which promote dynamicrecrystallization during rolling via the particle-stimulated nucleation phenomenon. As a result, the rolled AZ31–0.5Ca–0.5Gd (wt%) (AZXG3100) alloy shows a finer recrystallized grain structure than the rolled AZ31 alloy; the average grainsize of the former (11.9 μm) is considerably smaller than that of the latter (22.4 μm). The combined addition of Ca and Gdimproves the tensile yield strength of the rolled material from 131 to 144 MPa, which is attributed mainly to the combinedeffects of Hall–Petch hardening enhanced by grain refinement and dispersion hardening induced by the undissolved particles. The tensile elongation of the rolled material also increases from 14.6 to 18.3% upon the combined addition of Ca and Gd,because the activation of twinning during tension is less pronounced in the rolled AZXG3100 alloy owing to its smallergrain size. These results demonstrate that the combined addition of Ca and Gd simultaneously improves the tensile strengthand ductility of the rolled AZ31 alloy.
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High‑Strength AZ91 Alloy Fabricated by Rapidly Solidified Flaky Powder Metallurgy and Hot Extrusion
이태경,Michiaki Yamasaki,Yoshihito Kawamura,Jongbin Go,Sung Hyuk Park 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
A high-strength AZ91 alloy is produced via hot extrusion using flakes fabricated through the rapidly solidified flaky powdermetallurgy. The AZ91 alloy flakes have an extremely fine dendritic structure without any second-phase particles owing tothe fast cooling rate during solidification; these microstructural features considerably promote dynamic recrystallization andprecipitation behaviors during extrusion process. As a result, the AZ91 alloy extruded using the flakes exhibits an almostfully recrystallized microstructure with a very small average grain size of 1.2 μm owing to an increase in the number ofnucleation sites for recrystallization, and it shows a high microstructural homogeneity owing to the numerous Mg17Al12precipitates uniformly distributed throughout the material. This extruded AZ91 alloy has a tensile yield strength of 345 MPa,ultimate tensile strength of 417 MPa, and total elongation of 5.6%. These superior tensile strengths are mainly attributed tothe combined effects of precipitation hardening caused by abundant fine precipitates and grain boundary hardening causedby fine recrystallized grains.
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