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Ye Jin Kim

Bio: Ye Jin Kim is an academic researcher from Kyungpook National University. The author has contributed to research in topics: Ultimate tensile strength & Alloy. The author has an hindex of 9, co-authored 25 publications receiving 216 citations.

Papers
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Journal ArticleDOI
TL;DR: This paper showed that the precipitation behavior of β-Mg 17 Al 12 phase during aging and the resultant variation in hardness and mechanical properties of cast Mg-Al-Zn alloy are strongly dependent on initial grain size.

53 citations

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that the application of artificial water cooling during extrusion effectively increases the extrudability of the AZ91 alloy and significantly improves the mechanical properties of the extruded Mg alloy.
Abstract: This study demonstrates that the application of artificial water cooling during extrusion effectively increases the extrudability of the AZ91 alloy and significantly improves the mechanical properties of the extruded AZ91 alloy. The artificial cooling dramatically reduces the actual temperature of the deformation zone, which results in an increase in the maximum exit speed at which the alloy is extrudable without the occurrence of hot cracking from 4.5 m/min to 7.5 m/min. It also promotes dynamic recrystallization and precipitation behaviors during extrusion, which leads to a reduction in grain size and an increase in the amount of fine Mg 17 Al 12 precipitates. As a result, for the AZ91 alloy extruded at an exit speed of 1.5 m/min, the tensile and compressive yield strengths improve significantly by 51 MPa and 114 MPa, respectively, and its tension–compression yield asymmetry reduces from 0.73 to 1.02 owing to the refinement of the grain size by artificial cooling. In addition, the AZ91 alloy extruded at an exit speed of 7.5 m/min with artificial cooling exhibits a finer grain structure than and superior mechanical properties to the AZ91 alloy extruded at a slower exit speed of 4.5 m/min without artificial cooling. This result indicates that the application of artificial cooling can simultaneously improve the maximum extrusion speed and the tensile and compressive properties of Mg alloys.

42 citations

Journal ArticleDOI
TL;DR: In this paper, the texture of a rolled Mg alloy is effectively modified through the application of precompression and subsequent annealing treatment, leading to a remarkable improvement in the bending formability of the alloy at room temperature.

41 citations

Journal ArticleDOI
TL;DR: In this article, the microstructural evolution and underlying grain growth mechanism of a 10-12-twin-containing Mg alloy during annealing were investigated through quasi-in situ electron backscatter diffraction measurements of a rolled AZ31 alloy subjected to precompression along the rolling direction (RD).

40 citations

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that the addition of 4 ¾wt% Al to Mg-7Sn-1Zn alloy effectively promotes the dynamic recrystallization and dynamic precipitation behaviors during extrusion and significantly improves the tensile properties of the extruded alloy.

39 citations


Cited by
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Journal ArticleDOI
TL;DR: In 2018 and 2019, significant progress has been achieved in high-performance cast and wrought magnesium and magnesium alloys, such as Mg ion batteries, hydrogen storage Mg materials, bio-magnesium alloys and functional magnesium materials as discussed by the authors.

744 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of grain size on the strength and ductility of Mg alloys are summarized and fine-grained Mg-alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation methods are introduced.
Abstract: Magnesium (Mg) alloys, as the lightest metal engineering materials, have broad application prospects. However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simultaneously. Refining grain size via the deformation process based on the grain boundary strengthening and the transition of deformation mechanisms is one of the feasible strategies to prepare Mg alloys with high strength and high ductility. In this review, the effects of grain size on the strength and ductility of Mg alloys are summarized, and fine-grained Mg alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation technologies are introduced. Although some achievements have been made, the effects of grain size on various Mg alloys are rarely discussed systematically and some key mechanisms are unclear or lack direct microscopic evidence. This review can be used as a reference for further development of high-performance fine-grained Mg alloys.

111 citations

Journal ArticleDOI
TL;DR: In this article, an extruded Mg-1Gd alloy with a non-basal texture, whose basal poles are tilted 60.9° from the extrusion direction (ED), exhibits a high room-temperature tensile elongation of 37.2%.

80 citations

Journal ArticleDOI
TL;DR: In this article, a combined processing route of hot extrusion with multi-pass rotary die equal channel angular pressing (RD-ECAP) was applied to AZ91 Mg alloy with the aim of simultaneously improving its strength and ductility.
Abstract: A high strength, good ductility and cost-effective Mg alloy is highly desirable for the light-weighting application. Here, a combined processing route of hot extrusion with multi-pass rotary die equal channel angular pressing (RD-ECAP) was applied to AZ91 Mg alloy with the aim of simultaneously improving its strength and ductility. The anisotropic mechanical behavior of the ECAP alloy was investigated in comparison to the extruded alloy. The evolution of the microstructure and deformation texture was further examined as a function of the ECAP pass to construct the microstructure/texture-anisotropic properties link. The results indicate that the ECAP alloy exhibits a simultaneous improvement in both strength and ductility along three orthotropic directions compared to the as-cast alloy, and more ECAP passes continue this improvement trend. Thus, the optimal mechanical properties with the yield strength of 214.3–279.9 MPa, the ultimate tensile strength of 321.0–382.0 MPa, and the elongation of 8.2–15.5% along three tensile directions are achieved in the ECAP alloy after 12 passes RD-ECAP. This also implies a considerable anisotropy in the ECAP alloy, but it is significantly weakened compared to the extruded alloy. Moreover, it is found that the low ECAP pass (4 passes) is enough to achieve a homogenous microstructure, which is characterized by the uniform and fine equiaxed grains (~7 μm) with the fine β precipitates (~1.5 μm) along the grain boundaries. Therefore, the initial extrusion can accelerate the grain refinement and microstructure homogenization in subsequent ECAP processing. Increasing the ECAP passes over 4, there are no discernible changes in the grain and precipitate microstructures, but the texture migration is observed. The high strength of the ECAP alloys not only stems from the well-known refinement strengthening, but also for texture strengthening. The contribution of the texture strengthening is enhanced with the increase of the ECAP pass.

77 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of grain growth at elevated temperatures is discussed for a newly developed as-cast Mg-Gd-Al-Zn magnesium alloy, supported by fracture surface observations, texture analysis by Schulz reflection method based on X-ray diffraction (XRD), and work-hardening rate plots.
Abstract: The grain refinement by dynamic recrystallization (DRX), the enhancement of room-temperature strength and ductility by decreasing hot extrusion temperature, and the effect of grain growth at elevated temperatures are discussed for a newly developed as-cast Mg–Gd–Al–Zn magnesium alloy. The results are supported by fracture surface observations, texture analysis by Schulz reflection method based on X-ray diffraction (XRD), and work-hardening rate plots. It is found that by decreasing the extrusion temperature, the ductility of alloys enhances, which is related to the weakening of basal texture by the rare earth element Gd. Moreover, the grain growth annealing resulted in decreasing the strength and increasing the ductility in the conventional manner, where the texture intensity remained unchanged.

77 citations