Microstructure evolution and characterization of the adiabatic shear bands in AZ31 magnesium alloy

Liu, Xuanyu; Mao, Pingli; Zhou, Le; Wang, Zhi; Liu, Zheng; Wang, Rui

doi:10.1016/j.matchar.2023.112726

Cited by 13 publications

(6 citation statements)

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“…The DRX mechanism has been reported during transformed ASB formation in steels [79,87] and titanium [4,88], indicating that DRX nanograins are generated inside ASBs, while RDR has also been mentioned, resulting in the transformation of elongated sub-grains to ultrafine equiaxed grains via a 30 • rotation of grain boundaries [79]. In addition, the ASB neighboring microstructure, in the case of a dynamically compressed AZ31 magnesium alloy, has been separated into three regions regarding grain crystal orientation [89]. Specifically, the ASB core has shown a random crystal orientation composed of ultrafine equiaxed DRX grains, the ASB transition zone has revealed a textured crystal orientation and, finally, the surrounding matrix also showed a random orientation, as Figure 9 illustrates through a grain orientation diagram.…”

Section: Dynamic Recrystallizationmentioning

confidence: 99%

“…In contrast, discontinuous DRX nucleates the recrystallized grains along the initial grain boundaries and is responsible for local microstructural softening, providing a zigzag-like tendency in the stress-strain curve. Figure 10 depicts that the ASB core of the AZ31 alloy consists mainly of a recrystallized and deformed structure due to severe shear strain and a significant temperature rise, while the transition zone and surrounding matrix contain a substructure instead of a recrystallized one [89]. Also, the rising temperature during DRX is considered responsible for grain boundary migration and coalescence, revealing equiaxed nanograins of low-density imperfections [90].…”

Section: Dynamic Recrystallizationmentioning

confidence: 99%

“…AZ31 alloy consists mainly of a recrystallized and deformed structure due to severe shear strain and a significant temperature rise, while the transition zone and surrounding matrix contain a substructure instead of a recrystallized one [89]. Also, the rising temperature during DRX is considered responsible for grain boundary migration and coalescence, revealing equiaxed nanograins of low-density imperfections [90].…”

Section: Dynamic Recrystallizationmentioning

confidence: 99%

“…Following this, during the second step of the DRX mechanism, a strain increase reacts to grain elongation inside the ASB core (Figure 12d), while some of these grains are divided into smaller equiaxed nanograins, subjecting them to a rotation mechanism (Figure 12e). Finally, several micro-ASBs are gen- [89]. Reprinted from [89] with permission from Elsevier.…”

Section: Dynamic Recrystallizationmentioning

confidence: 99%

“…Figure 9. Grain orientation diagram in ASB neighboring microstructure for AZ31 Mg alloy under 1200 s −1 dynamic compression[89]. Reprinted from[89] with permission from Elsevier.…”

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confidence: 99%

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A Review on the Adiabatic Shear Banding Mechanism in Metals and Alloys Considering Microstructural Characteristics, Morphology and Fracture

Karantza,

Manolakos

2023

Metals

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The current review work studies the adiabatic shear banding (ASB) mechanism in metals and alloys, focusing on its microstructural characteristics, dominant evolution mechanisms and final fracture. An ASB reflects a thermomechanical deformation instability developed under high strain and strain rates, finally leading to dynamic fracture. An ASB initially occurs under severe shear localization, followed by a significant rise in temperature due to high strain rate adiabatic conditions. That temperature increase activates thermal softening and mechanical degradation mechanisms, reacting to strain instability and facilitating micro-voiding, which, through its coalescence, results in cracking failure. This work aims to summarize and review the critical characteristics of an ASB’s microstructure and morphology, evolution mechanisms, the propensity of materials against an ASB and fracture mechanisms in order to highlight their stage-by-stage evolution and attribute them a more consecutive behavior rather than an uncontrollable one. In that way, this study focuses on underlining some ASB aspects that remain fuzzy, allowing for further research, such as research on the interaction between thermal and damage softening regarding their contribution to ASB evolution, the conversion of strain energy to internal heat, which proved to be material-dependent instead of constant, and the strain rate sensitivity effect, which also concerns whether the temperature rise reflects a precursor or a result of ASB. Except for conventional metals and alloys like steels (low carbon, stainless, maraging, armox, ultra-high-strength steels, etc.), titanium alloys, aluminum alloys, magnesium alloys, nickel superalloys, uranium alloys, zirconium alloys and pure copper, the ASB propensity of nanocrystalline and ultrafine-grained materials, metallic-laminated composites, bulk metallic glasses and high-entropy alloys is also evaluated. Finally, the need to develop a micro-/macroscopic coupling during the thermomechanical approach to the ASB phenomenon is pointed out, highlighting the interaction between microstructural softening mechanisms and macroscopic mechanical behavior during ASB evolution and fracture.

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Section: Dynamic Recrystallizationmentioning

confidence: 99%

Section: Dynamic Recrystallizationmentioning

confidence: 99%

Section: Dynamic Recrystallizationmentioning

confidence: 99%

Section: Dynamic Recrystallizationmentioning

confidence: 99%

“…Figure 9. Grain orientation diagram in ASB neighboring microstructure for AZ31 Mg alloy under 1200 s −1 dynamic compression[89]. Reprinted from[89] with permission from Elsevier.…”

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confidence: 99%

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