Effect of Grain Refinement on Tensile Ductility in ZK60 Magnesium Alloy under Dynamic Loading

Mukai, Toshiji; Yamanoi, Masashi; Watanabe, Hiroyuki; Ito, Koichi; Higashi, Kenji

doi:10.2320/matertrans.42.1177

Cited by 121 publications

(55 citation statements)

References 10 publications

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“…1) Die casting and injection molding are the main method of manufacturing such components, 2) however, plastic forming technologies such as hot drawing and hot forging with high productivity have been developed to form thinner walls of the components without defects. 3,4) In the drawing process, it has been clearly demonstrated that the critical strain rate increase with the refinement of grain size in AZ31 magnesium alloy at 523 K. 5) Thus, grain size refinement of magnesium alloys is essential not only for the development of superior mechanical properties at room temperature such as higher strength, toughness 6,7) and ductility, 8) but also for the higher productivity. In general, dynamic restoration behavior is dependent on the stacking fault energy (SFE) and lattice diffusivity.…”

Section: Introductionmentioning

confidence: 99%

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

et al. 2008

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The effect of initial grain size on dynamically recrystallized grain size (DRX grain size) is examined in AZ31 magnesium alloy with four kinds of initial grain sizes. When the average grain size after the high-temperature compression test is plotted against Zenner-Hollomon parameter (Z-parameter), initial grain size dependence on DRX grain size appears only in the specimen with large initial grain size in the low Z region, but not in the specimen with small grain size or in high Z region. When the grain size measured only in recrystallized region is plotted against Z-parameter, initial grain size dependence on DRX grain size does not appear. From these results, it is concluded that there is no initial grain size dependence on DRX grain size when the DRX proceeds to some degree, because the DRX grain size becomes constant for a given Zvalue. The initial grain size dependence on DRX grain size observed in the low Z region would be related to the rotation of basal plane perpendicular to the compression axis during deformation before the DRX grains have been developed sufficiently.

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Section: Introductionmentioning

confidence: 99%

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

et al. 2008

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“…In general, tensile elongation of magnesium alloys increases with decreasing grain size. 24) However, the elongation did not decrease in spite of the grain coarsening.…”

Section: Rolled Amca602mentioning

confidence: 99%

Optimization of Rolling Conditions in Mg–Al–Ca Alloy Containing Insoluble Second Phase Particles

et al. 2008

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Hot rolling was conducted for Mg-6 mass%Al-2 mass%Ca alloy containing insoluble second phase particles and the mechanical properties of the rolled sheets were examined. The alloy used for rolling contained spherical particles with the size of 1.5 mm mainly in the grain boundaries. The amount of edge crack in the rolled sheets decreased at the rolling temperatures above $ 623 K. The highest strength and moderate elongation were obtained when the alloy was rolled at 623 K. The processing conditions for good workability under a given microstructure of the workpiece were considered from a viewpoint of relaxation of stress concentrations at the particle-matrix interface during rolling, and hot working diagrams were constructed. In order to attain good workability under the existence of relatively large second phase particles of 1.5 mm, it is required not only to activate the non-basal slip but also to make use of diffusional relaxation.

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“…It has been shown that pile-up of dislocations at the interface between the matrix and deformation twins caused stress concentration to form cracks [2]. Another study suggested that the ductility of Mg alloys is further limited under dynamic loading due to lowered activity of dislocations [3]. It has also been reported that a Mg-Al-Mn alloy had pronounced mechanical anisotropy at high strain rates of around 1.0×10 3 s -1 [4].…”

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Deformation Response of Mg-Y Alloys under Dynamic Loading

Mukai

Nagao

Terada

et al. 2015

Magnesium Technology 2015

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Extended AbstractWeight reduction of automobiles and aircrafts improves fuel economy and reduces greenhouse gas emissions. Use of Mg alloys may allow weight reduction because of their low densities, but adoption is hindered because they exhibit limited ductility at ambient temperatures [1]. In a previous study of fracture toughness in a Mg alloy, crack readily propagated near twin boundaries and resulted in poor durability [2]. It has been shown that pile-up of dislocations at the interface between the matrix and deformation twins caused stress concentration to form cracks [2]. Another study suggested that the ductility of Mg alloys is further limited under dynamic loading due to lowered activity of dislocations [3]. It has also been reported that a Mg-Al-Mn alloy had pronounced mechanical anisotropy at high strain rates of around 1.0×10 3 s -1 [4]. Therefore, the mechanical properties of Mg alloys should be evaluated accurately for applications involving possible dynamic loading.It has been reported that addition of rare earth elements such as yttrium may improve mechanical properties over conventional Mg-Al-Zn alloys by minimizing intensity of the basal texture [5][6][7][8][9]. However, the deformation behavior of Mg alloys containing yttrium is not sufficiently understood at strain rates exceeding 1×10 3 s -1 . This study examines a binary Mg-Y alloy at high strain rates in compression to clarify the effect of yttrium addition on the mechanical properties. Details have been reported elsewhere [10].This study investigated a binary Mg-0.6at.%Y alloy. A billet was fabricated by gravity casting into a steel mold. The cast binary alloy was homogenized at 773 K, followed by quenching in water. It was then extruded at 673 K at a ratio of 25:1. The extruded rod having a diameter of 8 mm was annealed at 673 K for 16.5 h to form an equiaxed grain structure with an average grain size of 42 μm. As a reference material, extruded magnesium with 99.95% purity and an average grain size of 50 μm was prepared. Cylindrical specimens having a height of 8 mm and a diameter of 4 mm were machined parallel to the extrusion direction. To examine the mechanical anisotropy, cylindrical specimens of height 6.5 mm and diameter 4 mm were also prepared along two directions, parallel and perpendicular to the extrusion direction. High strain rate compression tests were performed by using a split Hopkinson pressure bar (SHPB) at ambient temperature (298 K). The average strain rate was measured to be 1.4×10 3 s -1 for a specimen of 8.0 mm height and to be 1.7×10 3 s -1 for a specimen of 6.5 mm height. The shape of the specimen during deformation was detected as a series of images by an ultra-high speed camera (Shimadzu HPV-1) with a sampling time of 4 μs.By investigation of the Mg-0.6 at.% Y alloy and comparing it with a commercial purity magnesium sample, we have found that yttrium solute contributed to enhanced compressive ductility, reduced strain hardening rate, and minimized deformation asymmetry in magnesium, even under dynamic loading. ...

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Effect of Grain Refinement on Tensile Ductility in ZK60 Magnesium Alloy under Dynamic Loading

Cited by 121 publications

References 10 publications

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

Optimization of Rolling Conditions in Mg–Al–Ca Alloy Containing Insoluble Second Phase Particles

Deformation Response of Mg-Y Alloys under Dynamic Loading

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Effect of Grain Refinement on Tensile Ductility in ZK60 Magnesium Alloy under Dynamic Loading

Cited by 121 publications

References 10 publications

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

Optimization of Rolling Conditions in Mg&ndash;Al&ndash;Ca Alloy Containing Insoluble Second Phase Particles

Deformation Response of Mg-Y Alloys under Dynamic Loading

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Optimization of Rolling Conditions in Mg–Al–Ca Alloy Containing Insoluble Second Phase Particles