TY - JOUR

T1 - Ultra-severe plastic deformation

T2 - Evolution of microstructure, phase transformation and hardness in immiscible magnesium-based systems

AU - Edalati, Kaveh

AU - Uehiro, Ryoko

AU - Fujiwara, Keisuke

AU - Ikeda, Yuji

AU - Li, Hai Wen

AU - Sauvage, Xavier

AU - Valiev, Ruslan Z.

AU - Akiba, Etsuo

AU - Tanaka, Isao

AU - Horita, Zenji

PY - 2017/7/31

Y1 - 2017/7/31

N2 - Although severe plastic deformation (SPD) alters the microstructure and phase transformation at the early stages of straining, the microstructural features finally saturate to the steady states at large shear strains. However, from the atomic point of view, to achieve the steady state in immiscible systems with positive heat of mixing, the minimum shear strain should be so high that the thickness of sheared phases becomes comparable to one atomic distance. In this study, ultrahigh shear strains up to ~70,000 are introduced in different Mg-based immiscible systems by high-pressure torsion (HPT) method for up to 1500 turns. New metastable phases are formed in most of the selected magnesium alloys by ultra-SPD, in good agreement with the first-principles calculations. However, the microstructural/structural saturation hardly occurs in many alloys even at ultrahigh strains. The materials processed by ultra-SPD exhibit unique hardness-strain and tensile behaviors which cannot be observed after conventional SPD.

AB - Although severe plastic deformation (SPD) alters the microstructure and phase transformation at the early stages of straining, the microstructural features finally saturate to the steady states at large shear strains. However, from the atomic point of view, to achieve the steady state in immiscible systems with positive heat of mixing, the minimum shear strain should be so high that the thickness of sheared phases becomes comparable to one atomic distance. In this study, ultrahigh shear strains up to ~70,000 are introduced in different Mg-based immiscible systems by high-pressure torsion (HPT) method for up to 1500 turns. New metastable phases are formed in most of the selected magnesium alloys by ultra-SPD, in good agreement with the first-principles calculations. However, the microstructural/structural saturation hardly occurs in many alloys even at ultrahigh strains. The materials processed by ultra-SPD exhibit unique hardness-strain and tensile behaviors which cannot be observed after conventional SPD.

KW - DFT calculations

KW - Magnesium alloys

KW - Nanostructured materials

KW - Phase transition

KW - Severe plastic deformation (SPD)

KW - Ultrafine-grained (UFG) materials

UR - http://www.scopus.com/inward/record.url?scp=85021242458&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2017.06.076

DO - 10.1016/j.msea.2017.06.076

M3 - Article

AN - SCOPUS:85021242458

VL - 701

SP - 158

EP - 166

JO - Materials Science and Engineering: A

JF - Materials Science and Engineering: A

SN - 0921-5093

ER -