Dynamic recrystallization of titanium: Effect of pre-activated twinning at cryogenic temperature
| Autor: | S.J. Qu, C.K. Yan, Cao Guojian, A.H. Feng, Daolun Chen, J.L. Sun, Jun Shen |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Materials science Polymers and Plastics Deformation (mechanics) Metals and Alloys chemistry.chemical_element Thermodynamics 02 engineering and technology Slip (materials science) Flow stress Strain hardening exponent 021001 nanoscience & nanotechnology 01 natural sciences Electronic Optical and Magnetic Materials chemistry 0103 physical sciences Ceramics and Composites Dynamic recrystallization 0210 nano-technology Crystal twinning Softening Titanium |
| Zdroj: | Acta Materialia. 154:311-324 |
| ISSN: | 1359-6454 |
| DOI: | 10.1016/j.actamat.2018.05.057 |
| Popis: | A pre-cold-deformation process was applied for commercially pure titanium at cryogenic temperature to activate high-density deformation twins, and subsequent hot-deformation was used to induce dynamic recrystallization (DRX). Three major types of twins were effectively activated during cryogenic deformation, including { 11 2 ¯ 2 } contraction twins, { 11 2 ¯ 1 } extension twins, and { 10 1 ¯ 2 } extension twins. A special type of slipped { 11 2 ¯ 1 } “twins” was also activated by a sequential effect of twinning and slip. Selection of twinning variants followed Schmid's law well, where only the twinning systems with a Schmid factor of m ≥ 0.4 could be activated. The pre-activated twinning led to a remarkably stable flow stress at 500 °C up to a true strain of 1.0, due to the attainment of dynamic equilibrium between strain hardening and high-temperature softening. Two DRX stages occurred: (1) twin-active DRX stage, and (2) discontinuous dynamic recrystallization (DDRX) stage. The DRX mechanisms identified were twinning-induced DRX (or TDRX) and DDRX. While the low-temperature slip alone had little influence on DRX, the pre-activated { 11 2 ¯ 2 } twins, { 11 2 ¯ 1 } twins, { 10 1 ¯ 2 } twins and slipped { 11 2 ¯ 1 } “twins” contributed effectively to DRX in the form of spheroidization of twin lamellae due to twin-dislocation interactions, leading to a substantial grain refinement from ∼41 to ∼1 μm during subsequent hot-deformation. |
| Databáze: | OpenAIRE |
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