Recent Advances in the Grain Refinement Effects of Zr on Mg Alloys: A Review

Sun, Ming; Yang, Daoguo; Mao, Lin; Li, Xikuo; Pang, Song

doi:10.3390/met12081388

Cited by 19 publications

(3 citation statements)

References 74 publications

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“…Second, the widely accepted theory for grain refinement during solidification for various alloys is still the inoculation effect, e.g. Ti with B in Al [52], Zr in Mg, or Al [53]. This mechanism seems impossible for hypoeutectic Ti-B alloys when β-phase grains are solidified before the eutectic-originated TiB phase [54].…”

Section: Discussionmentioning

confidence: 99%

Boron Effect on Microstructure, Superplastic Behavior, and Mechanical Properties of Ti-4Al-3Mo-1V Alloy

Postnikova¹,

Котов²,

Базлов³

et al. 2023

Preprint

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The microstructure evolution, superplasticity, and room temperature mechanical properties of Ti-4%Al-1%V-3%Mo alloys modified with 0.01-2 wt.% boron were investigated. Increasing the boron content from 0 to 0.1 wt.% effectively refined prior β-grains, reducing a mean grain size from ~700 µm to ~210 µm. Whiskers of the TiB phase with a size in a range of 0.7-2.9 µm were observed after solidification and thermomechanical processing. Alloys with 0.01-0.1 wt.% boron exhibited similar superplastic elongations and strain rate sensitivity coefficient m of 0.4-0.5 at a strain rate of 1×10-3 s-1 and the elongation to failure decreased from 1000% at 875°С to 400-500% at 700°С. Along with this, the minor boron addition effectively decreased flow stress values, especially at 775 °C, that was explained by the acceleration of the recrystallization and globularization of the microstructure at the initial stage of deformation. Recrystallization-induced decrease in yield strength from 770 MPa to 680 MPa was observed with an increase in boron content from 0 to 0.1 wt.%. Heat treatment increased post-forming strength characteristics for the alloys with 0.01-0.1 wt.% boron by 90–140 MPa without ductility reduction. Alloys with 1-2 wt.% B demonstrated the opposite behavior. The grain refinement effect was not revealed, and prior β grain sizes were ~670-750 µm after solidification. Thermomechanical processing promoted the fragmentation of boride whiskers and the formation of near-spherical particles with a size of ~1 μm for the alloy with a eutectic concentration of 2 wt.% B. A high fraction of borides, ~5-11%, in the alloys with 1-2 wt.% B deteriorated the superplastic properties and drastically decreased ductility at room temperature. The alloy with 2 wt.% B demonstrated non-superplastic behavior and a low level of mechanical properties, meanwhile, the alloy with 1% boron exhibited high-temperature superplasticity at 875 °C with elongation of ~500%, and yield strength of 830 MPa, ultimate tensile strength of 1020 MPa at a room temperature after 100% of superplastic deformation.

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Section: Discussionmentioning

confidence: 99%

Boron Effect on Microstructure, Superplastic Behavior, and Mechanical Properties of Ti-4Al-3Mo-1V Alloy

Postnikova¹,

Котов²,

Базлов³

et al. 2023

Preprint

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show abstract

“…A segregation effect is the most pronounced at the minor content of alloying element or impurity and the distribution of the elements became more homogeneous at its high content [ 16 ]. Second, the widely accepted theory for grain refinement during solidification for various alloys is still the inoculation effect, e.g., Ti with B in Al [ 48 ], Zr in Mg, or Al [ 49 ]. This mechanism seems impossible for hypoeutectic Ti-B alloys when β -phase grains are solidified before the eutectic-originated TiB phase [ 50 ].…”

Section: Discussionmentioning

confidence: 99%

Effect of Boron on the Microstructure, Superplastic Behavior, and Mechanical Properties of Ti-4Al-3Mo-1V Alloy

et al. 2023

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The decrease of superplastic forming temperature and improvement of post-forming mechanical properties are important issues for titanium-based alloys. Ultrafine-grained and homogeneous microstructure are required to improve both processing and mechanical properties. This study focuses on the influence of 0.01–2 wt.% B (boron) on the microstructure and properties of Ti-4Al-3Mo-1V (wt.%) alloys. The microstructure evolution, superplasticity, and room temperature mechanical properties of boron-free and boron-modified alloys were investigated using light optical microscopy, scanning electron microscopy, electron backscatter diffraction, X-ray diffraction analysis, and uniaxial tensile tests. A trace addition of 0.01 to 0.1 wt.% B significantly refined prior β-grains and improved superplasticity. Alloys with minor B and B-free alloy exhibited similar superplastic elongations of 400–1000% in a temperature range of 700–875 °C and strain rate sensitivity coefficient m of 0.4–0.5. Along with this, a trace boron addition provided a stable flow and effectively reduced flow stress values, especially at low temperatures, that was explained by the acceleration of the recrystallization and globularization of the microstructure at the initial stage of superplastic deformation. Recrystallization-induced decrease in yield strength from 770 MPa to 680 MPa was observed with an increase in boron content from 0 to 0.1%. Post-forming heat treatment, including quenching and ageing, increased strength characteristics of the alloys with 0.01 and 0.1% boron by 90–140 MPa and insignificantly decreased ductility. Alloys with 1–2% B exhibited an opposite behavior. For the high-boron alloys, the refinement effect of the prior β-grains was not detected. A high fraction of borides of ~5–11% deteriorated the superplastic properties and drastically decreased ductility at room temperature. The alloy with 2% B demonstrated non-superplastic behavior and low level of strength properties; meanwhile, the alloy with 1% B exhibited superplasticity at 875 °C with elongation of ~500%, post-forming yield strength of 830 MPa, and ultimate tensile strength of 1020 MPa at room temperature. The differences between minor boron and high boron influence on the grain structure and properties were discussed and the mechanisms of the boron influence were suggested.

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“…Sun et al [11] reported the latest progress on the effect of Zr in the grain refinement of magnesium alloys. The Mg-Zr master alloy ensured a clean interface between the Zr particles and Mg solution, which was beneficial to the diffusion of Zr elements and improved the utilization rate of nucleation.…”

Section: Contributionsmentioning

confidence: 99%